DOTS T. Reddy
Internet-Draft McAfee
Intended status: Standards Track M. Boucadair
Expires: June 16, 2018 Orange
P. Patil
Cisco
A. Mortensen
Arbor Networks, Inc.
N. Teague
Verisign, Inc.
December 13, 2017
Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal
Channel
draft-ietf-dots-signal-channel-13
Abstract
This document specifies the DOTS signal channel, a protocol for
signaling the need for protection against Distributed Denial-of-
Service (DDoS) attacks to a server capable of enabling network
traffic mitigation on behalf of the requesting client.
A companion document defines the DOTS data channel, a separate
reliable communication layer for DOTS management and configuration
purposes.
Editorial Note (To be removed by RFC Editor)
Please update these statements with the RFC number to be assigned to
this document:
o "This version of this YANG module is part of RFC XXXX;"
o "RFC XXXX: Distributed Denial-of-Service Open Threat Signaling
(DOTS) Signal Channel";
o "| 3.00 | Alternate server | [RFCXXXX] |"
o reference: RFC XXXX
o This RFC
Please update TBD statements with the port number to be assigned to
DOTS Signal Channel Protocol.
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Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on June 16, 2018.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Notational Conventions and Terminology . . . . . . . . . . . 5
3. Design Overview . . . . . . . . . . . . . . . . . . . . . . . 6
4. DOTS Signal Channel: Messages & Behaviors . . . . . . . . . . 8
4.1. DOTS Server(s) Discovery . . . . . . . . . . . . . . . . 8
4.2. CoAP URIs . . . . . . . . . . . . . . . . . . . . . . . . 8
4.3. Happy Eyeballs for DOTS Signal Channel . . . . . . . . . 9
4.4. DOTS Mitigation Methods . . . . . . . . . . . . . . . . . 10
4.4.1. Request Mitigation . . . . . . . . . . . . . . . . . 11
4.4.2. Retrieve Information Related to a Mitigation . . . . 20
4.4.3. Efficacy Update from DOTS Clients . . . . . . . . . . 28
4.4.4. Withdraw a Mitigation . . . . . . . . . . . . . . . . 30
4.5. DOTS Signal Channel Session Configuration . . . . . . . . 32
4.5.1. Discover Configuration Parameters . . . . . . . . . . 33
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4.5.2. Convey DOTS Signal Channel Session Configuration . . 35
4.5.3. Delete DOTS Signal Channel Session Configuration . . 40
4.6. Redirected Signaling . . . . . . . . . . . . . . . . . . 40
4.7. Heartbeat Mechanism . . . . . . . . . . . . . . . . . . . 42
5. DOTS Signal Channel YANG Module . . . . . . . . . . . . . . . 43
5.1. Tree Structure . . . . . . . . . . . . . . . . . . . . . 43
5.2. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 45
6. Mapping Parameters to CBOR . . . . . . . . . . . . . . . . . 55
7. (D)TLS Protocol Profile and Performance Considerations . . . 56
7.1. (D)TLS Protocol Profile . . . . . . . . . . . . . . . . . 56
7.2. (D)TLS 1.3 Considerations . . . . . . . . . . . . . . . . 58
7.3. MTU and Fragmentation . . . . . . . . . . . . . . . . . . 59
8. Mutual Authentication of DOTS Agents & Authorization of DOTS
Clients . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 61
9.1. DOTS Signal Channel UDP and TCP Port Number . . . . . . . 61
9.2. Well-Known 'dots' URI . . . . . . . . . . . . . . . . . . 61
9.3. CoAP Response Code . . . . . . . . . . . . . . . . . . . 61
9.4. DOTS Signal Channel CBOR Mappings Registry . . . . . . . 62
9.4.1. Registration Template . . . . . . . . . . . . . . . . 62
9.4.2. Initial Registry Contents . . . . . . . . . . . . . . 62
9.5. DOTS Signal Channel YANG Module . . . . . . . . . . . . . 68
10. Implementation Status . . . . . . . . . . . . . . . . . . . . 68
10.1. nttdots . . . . . . . . . . . . . . . . . . . . . . . . 69
11. Security Considerations . . . . . . . . . . . . . . . . . . . 69
12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 70
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 70
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 71
14.1. Normative References . . . . . . . . . . . . . . . . . . 71
14.2. Informative References . . . . . . . . . . . . . . . . . 73
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 76
1. Introduction
A distributed denial-of-service (DDoS) attack is an attempt to make
machines or network resources unavailable to their intended users.
In most cases, sufficient scale can be achieved by compromising
enough end-hosts and using those infected hosts to perpetrate and
amplify the attack. The victim in this attack can be an application
server, a host, a router, a firewall, or an entire network.
Network applications have finite resources like CPU cycles, the
number of processes or threads they can create and use, the maximum
number of simultaneous connections it can handle, the limited
resources of the control plane, etc. When processing network
traffic, such applications are supposed to use these resources to
offer the intended task in the most efficient manner. However, a
DDoS attacker may be able to prevent an application from performing
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its intended task by making the application exhaust its finite
resources.
TCP DDoS SYN-flood, for example, is a memory-exhausting attack while
ACK-flood is a CPU-exhausting attack [RFC4987]. Attacks on the link
are carried out by sending enough traffic so that the link becomes
congested, thereby likely causing packet loss for legitimate traffic.
Stateful firewalls can also be attacked by sending traffic that
causes the firewall to maintain an excessive number of states that
may jeopardize the firewall's operation overall, besides like
performance impacts. The firewall then runs out of memory, and can
no longer instantiate the states required to process legitimate
flows. Other possible DDoS attacks are discussed in [RFC4732].
In many cases, it may not be possible for network administrators to
determine the cause(s) of an attack. They may instead just realize
that certain resources seem to be under attack. This document
defines a lightweight protocol that allows a DOTS client to request
mitigation from one or more DOTS servers for protection against
detected, suspected, or anticipated attacks. This protocol enables
cooperation between DOTS agents to permit a highly-automated network
defense that is robust, reliable, and secure.
An example of a network diagram that illustrates a deployment of DOTS
agents is shown in Figure 1. In this example, a DOTS server is
operating on the access network. A DOTS client is located on the LAN
(Local Area Network), while a DOTS gateway is embedded in the CPE
(Customer Premises Equipment).
Network
Resource CPE router Access network __________
+-----------+ +--------------+ +-------------+ / \
| |____| |_______| |___ | Internet |
|DOTS client| | DOTS gateway | | DOTS server | | |
| | | | | | | |
+-----------+ +--------------+ +-------------+ \__________/
Figure 1: Sample DOTS Deployment (1)
DOTS servers can also be reachable over the Internet, as depicted in
Figure 2.
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Network DDoS mitigation
Resource CPE router __________ service
+-----------+ +-------------+ / \ +-------------+
| |____| |_______| |___ | |
|DOTS client| |DOTS gateway | | Internet | | DOTS server |
| | | | | | | |
+-----------+ +-------------+ \__________/ +-------------+
Figure 2: Sample DOTS Deployment (2)
In typical deployments, the DOTS client belongs to a different
administrative domain than the DOTS server. For example, the DOTS
client is embedded in a firewall protecting services owned and
operated by a domain, while the DOTS server is owned and operated by
a different domain providing DDoS mitigation services. The latter
might or might not provide connectivity services to the network
hosting the DOTS client.
The DOTS server may (not) be co-located with the DOTS mitigator. In
typical deployments, the DOTS server belongs to the same
administrative domain as the mitigator. The DOTS client can
communicate directly with a DOTS server or indirectly via a DOTS
gateway.
The document adheres to the DOTS architecture
[I-D.ietf-dots-architecture]. The requirements for DOTS signal
channel protocol are documented in [I-D.ietf-dots-requirements].
This document satisfies all the use cases discussed in
[I-D.ietf-dots-use-cases].
This document focuses on the DOTS signal channel. This is a
companion document of the DOTS data channel specification
[I-D.ietf-dots-data-channel] that defines a configuration and a bulk
data exchange mechanism supporting the DOTS signal channel.
2. Notational Conventions and Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
(D)TLS is used for statements that apply to both Transport Layer
Security [RFC5246] and Datagram Transport Layer Security [RFC6347].
Specific terms will be used for any statement that applies to either
protocol alone.
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The reader should be familiar with the terms defined in
[I-D.ietf-dots-architecture].
The meaning of the symbols in YANG tree diagrams is defined in
[I-D.ietf-netmod-yang-tree-diagrams].
3. Design Overview
The DOTS signal channel is built on top of the Constrained
Application Protocol (CoAP) [RFC7252], a lightweight protocol
originally designed for constrained devices and networks. The many
features of CoAP (expectation of packet loss, support for
asynchronous non-confirmable messaging, congestion control, small
message overhead limiting the need for fragmentation, use of minimal
resources, and support for (D)TLS) makes it a good candidate to build
the DOTS signaling mechanism from.
The DOTS signal channel is layered on existing standards (Figure 3).
+--------------+
| DOTS |
+--------------+
| CoAP |
+--------------+
| TLS | DTLS |
+--------------+
| TCP | UDP |
+--------------+
| IP |
+--------------+
Figure 3: Abstract Layering of DOTS signal channel over CoAP over
(D)TLS
By default, a DOTS signal channel MUST run over port number TBD as
defined in Section 9.1, for both UDP and TCP, unless the DOTS server
has a mutual agreement with its DOTS clients to use a different port
number. DOTS clients may alternatively support means to dynamically
discover the ports used by their DOTS servers. In order to use a
distinct port number (as opposed to TBD), DOTS clients and servers
should support a configurable parameter to supply the port number to
use. The rationale for not using the default port number 5684
((D)TLS CoAP) is to allow for differentiated behaviors in
environments where both a DOTS gateway and an IoT gateway (e.g.,
Figure 3 of [RFC7452]) are present.
The signal channel is initiated by the DOTS client (Section 4.4).
Once the signal channel is established, the DOTS agents periodically
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send heartbeats to keep the channel active (Section 4.7). At any
time, the DOTS client may send a mitigation request message to a DOTS
server over the active channel. While mitigation is active because
of the higher likelihood of packet loss during a DDoS attack, the
DOTS server periodically sends status messages to the client,
including basic mitigation feedback details. Mitigation remains
active until the DOTS client explicitly terminates mitigation, or the
mitigation lifetime expires.
DOTS signaling can happen with DTLS [RFC6347] over UDP and TLS
[RFC5246] over TCP. Likewise, DOTS requests may be sent using IPv4
or IPv6 transfer capabilities. A Happy Eyeballs procedure for DOTS
signal channel is specified in Section 4.3.
Messages exchanged between DOTS agents are serialized using Concise
Binary Object Representation (CBOR) [RFC7049], CBOR is a binary
encoding scheme designed for small code and message size. CBOR-
encoded payloads are used to carry signal channel-specific payload
messages which convey request parameters and response information
such as errors. In order to allow the use of the same data models,
[RFC7951] specifies the JSON encoding of YANG-modeled data. A
similar effort for CBOR is defined in [I-D.ietf-core-yang-cbor].
From that standpoint, this document specifies a YANG data model for
representing mitigation scopes and DOTS signal channel session
configuration data (Section 5). Representing these data as CBOR data
is assumed to follow the rules in [I-D.ietf-core-yang-cbor] or those
in [RFC7951] combined with JSON/CBOR conversion rules in [RFC7049].
In order to prevent fragmentation, DOTS agents must follow the
recommendations documented in Section 4.6 of [RFC7252]. Refer to
Section 7.3 for more details.
DOTS agents MUST support GET, PUT, and DELETE CoAP methods. The
payload included in CoAP responses with 2.xx and 3.xx Response Codes
MUST be of content type "application/cbor" (Section 5.5.1 of
[RFC7252]). CoAP responses with 4.xx and 5.xx error Response Codes
MUST include a diagnostic payload (Section 5.5.2 of [RFC7252]). The
Diagnostic Payload may contain additional information to aid
troubleshooting.
In deployments where multiple DOTS clients are enabled in a network
(owned and operated by the same entity), the DOTS server may detect
conflicting mitigation requests from these clients. This document
does not aim to specify a comprehensive list of conditions under
which a DOTS server will characterize two mitigation requests from
distinct DOTS clients as conflicting, nor recommend a DOTS server
behavior for processing conflicting mitigation requests. Those
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considerations are implementation- and deployment-specific.
Nevertheless, the document specifies the mechanisms to notify DOTS
clients when conflicts occur, including the conflict cause
(Section 4.4).
In deployments where one or more translators (e.g., NAT44, NAT64,
NPTv6) are enabled between the client's network and the DOTS server,
DOTS signal channel messages forwarded to a DOTS server must not
include internal IP addresses/prefixes and/or port numbers; external
addresses/ prefixes and/or port numbers as assigned by the translator
must be used instead. This document does not make any recommendation
about possible translator discovery mechanisms. The following are
some (non-exhaustive) deployment examples that may be considered:
o Port Control Protocol (PCP) [RFC6887] or Session Traversal
Utilities for NAT (STUN) [RFC5389] may be used to retrieve the
external addresses/prefixes and/or port numbers. Information
retrieved by means of PCP will be used to feed the DOTS signal
channel messages that will be sent to a DOTS server.
o A DOTS gateway may be co-located with the translator. The DOTS
gateway will need to update the DOTS messages, based upon the
local translator's binding table.
4. DOTS Signal Channel: Messages & Behaviors
4.1. DOTS Server(s) Discovery
This document assumes that DOTS clients are provisioned with the
reachability information of their DOTS server(s) using a variety of
means (e.g., local configuration, or dynamic means such as DHCP).
These means are out of scope of this document.
Likewise, it is out of scope of this document to specify the behavior
of a DOTS client when it sends requests (e.g., contact all servers,
select one server among the list) when multiple DOTS servers are
provisioned.
4.2. CoAP URIs
The DOTS server MUST support the use of the path-prefix of "/.well-
known/" as defined in [RFC5785] and the registered name of "dots".
Each DOTS operation is indicated by a path-suffix that indicates the
intended operation. The operation path (Table 1) is appended to the
path-prefix to form the URI used with a CoAP request to perform the
desired DOTS operation.
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+-----------------------+----------------+-------------+
| Operation | Operation path | Details |
+-----------------------+----------------+-------------+
| Mitigation | /v1/mitigate | Section 4.4 |
+-----------------------+----------------+-------------+
| Session configuration | /v1/config | Section 4.5 |
+-----------------------+----------------+-------------+
Table 1: Operations and their corresponding URIs
4.3. Happy Eyeballs for DOTS Signal Channel
DOTS signaling can operate with DTLS over UDP and TLS over TCP. A
DOTS client can use DNS to determine the IP address(es) of a DOTS
server or a DOTS client may be provided with the list of the IP
addresses of various DOTS servers. The DOTS client MUST know a DOTS
server's domain name; hard-coding the domain name of the DOTS server
into software is NOT RECOMMENDED in case the domain name is not valid
or needs to change for legal or other reasons. The DOTS client
performs A and/or AAAA record lookup of the domain name and the
result will be a list of IP addresses, each of which can be used to
contact the DOTS server using UDP and TCP.
If an IPv4 path to reach a DOTS server is found, but the DOTS
server's IPv6 path is not working, a dual-stack DOTS client can
experience a significant connection delay compared to an IPv4-only
DOTS client. The other problem is that if a middlebox between the
DOTS client and DOTS server is configured to block UDP traffic, the
DOTS client will fail to establish a DTLS session with the DOTS
server and , as a consequence, will have to fall back to TLS over
TCP, thereby incurring significant connection delays.
[I-D.ietf-dots-requirements] mentions that DOTS agents will have to
support both connectionless and connection-oriented protocols.
To overcome these connection setup problems, the DOTS client can
attempt to connect to the DOTS server using both IPv6 and IPv4, and
try both DTLS over UDP and TLS over TCP in a manner similar to the
Happy Eyeballs mechanism [RFC6555]. These connection attempts are
performed by the DOTS client when it initializes, and the DOTS client
uses the results of the Happy Eyeballs procedure for sending its
subsequent messages to the DOTS server.
In order of preference (most preferred first), it is UDP over IPv6,
UDP over IPv4, TCP over IPv6, and finally TCP over IPv4, which
adheres to address preference order [RFC6724] and the DOTS
preference, which privileges the use of UDP over TCP (to avoid TCP's
head of line blocking).
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DOTS client DOTS server
| |
|--DTLS ClientHello, IPv6 ---->X |
|--TCP SYN, IPv6-------------->X |
|--DTLS ClientHello, IPv4 ---->X |
|--TCP SYN, IPv4----------------------------------------->|
|--DTLS ClientHello, IPv6 ---->X |
|--TCP SYN, IPv6-------------->X |
|<-TCP SYNACK---------------------------------------------|
|--DTLS ClientHello, IPv4 ---->X |
|--TCP ACK----------------------------------------------->|
|<------------Establish TLS Session---------------------->|
|----------------DOTS signal----------------------------->|
| |
Figure 4: DOTS Happy Eyeballs
In reference to Figure 4, the DOTS client sends two TCP SYNs and two
DTLS ClientHello messages at the same time over IPv6 and IPv4. In
this example, it is assumed that the IPv6 path is broken and UDP is
dropped by a middlebox but has little impact to the DOTS client
because there is no long delay before using IPv4 and TCP. The DOTS
client repeats the mechanism to discover if DOTS signaling with DTLS
over UDP becomes available from the DOTS server, so the DOTS client
can migrate the DOTS signal channel from TCP to UDP. But such
probing SHOULD NOT be done more frequently than every 24 hours and
MUST NOT be done more frequently than every 5 minutes.
4.4. DOTS Mitigation Methods
The following methods are used by a DOTS client to request, withdraw,
or retrieve the status of mitigation requests:
PUT: DOTS clients use the PUT method to request mitigation from a
DOTS server (Section 4.4.1). During active mitigation, DOTS
clients may use PUT requests to carry mitigation efficacy
updates to the DOTS server (Section 4.4.3).
GET: DOTS clients may use the GET method to subscribe to DOTS
server status messages, or to retrieve the list of its
mitigations maintained by a DOTS server (Section 4.4.2).
DELETE: DOTS clients use the DELETE method to withdraw a request for
mitigation from a DOTS server (Section 4.4.4).
Mitigation request and response messages are marked as Non-
confirmable messages (Section 2.2 of [RFC7252]).
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DOTS agents SHOULD follow the data transmission guidelines discussed
in Section 3.1.3 of [RFC8085] and control transmission behavior by
not sending more than one UDP datagram per RTT to the peer DOTS agent
on average.
Requests marked by the DOTS client as Non-confirmable messages are
sent at regular intervals until a response is received from the DOTS
server. If the DOTS client cannot maintain an RTT estimate, it
SHOULD NOT send more than one Non-confirmable request every 3
seconds, and SHOULD use an even less aggressive rate whenever
possible (case 2 in Section 3.1.3 of [RFC8085]).
4.4.1. Request Mitigation
When a DOTS client requires mitigation for some reason, the DOTS
client uses the CoAP PUT method to send a mitigation request to its
DOTS server(s) (Figure 5, illustrated in JSON diagnostic notation).
If this DOTS client is entitled to solicit the DOTS service, the DOTS
server can enable mitigation on behalf of the DOTS client by
communicating the DOTS client's request to the mitigator and relaying
selected mitigator feedback to the requesting DOTS client.
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Header: PUT (Code=0.03)
Uri-Host: "host"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "version"
Uri-Path: "mitigate"
Content-Type: "application/cbor"
{
"mitigation-scope": {
"client-identifier": [
"string"
],
"scope": [
{
"mitigation-id": integer,
"target-prefix": [
"string"
],
"target-port-range": [
{
"lower-port": integer,
"upper-port": integer
}
],
"target-protocol": [
integer
],
"target-fqdn": [
"string"
],
"target-uri": [
"string"
],
"alias-name": [
"string"
],
"lifetime": integer
}
]
}
}
Figure 5: PUT to convey DOTS mitigation requests
The parameters are described below:
client-identifier: The client identifier MAY be conveyed by the DOTS
gateway to propagate the DOTS client identity from the gateway's
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client-side to the gateway's server-side, and from the gateway's
server-side to the DOTS server. This allows the DOTS server to
accept mitigation requests with scopes which the DOTS client is
authorized to manage.
The 'client-identifier' value MUST be assigned by the DOTS gateway
in a manner that ensures that there is zero probability that the
same value will be assigned to a different DOTS client. The DOTS
gateway MUST conceal potentially sensitive DOTS client identity
information. The client-identifier attribute SHOULD NOT be
generated and included by the DOTS client.
This is an optional attribute.
mitigation-id: Identifier for the mitigation request represented
with an integer. This identifier MUST be unique for each
mitigation request bound to the DOTS client, i.e., the mitigation-
id parameter value in the mitigation request needs to be unique
relative to the mitigation-id parameter values of active
mitigation requests conveyed from the DOTS client to the DOTS
server. This identifier MUST be generated by the DOTS client.
This document does not make any assumption about how this
identifier is generated.
This is a mandatory attribute.
target-prefix: A list of prefixes identifying resources under
attack. Prefixes are represented using Classless Inter-Domain
Routing (CIDR) notation [RFC4632].
As a reminder, the prefix length must be less than or equal to 32
(resp. 128) for IPv4 (resp. IPv6).
This is an optional attribute.
target-port-range: A list of port numbers bound to resources under
attack.
The port range is defined by two bounds, a lower port number
(lower-port) and an upper port number (upper-port). When only
'lower-port' is present, it represents a single port number. For
TCP, UDP, Stream Control Transmission Protocol (SCTP) [RFC4960],
or Datagram Congestion Control Protocol (DCCP) [RFC4340], the
range of ports can be, for example, 1024-65535.
This is an optional attribute.
target-protocol: A list of protocols involved in an attack. Values
are taken from the IANA protocol registry [proto_numbers].
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The value 0 has a special meaning for 'all protocols'.
This is an optional attribute.
target-fqdn: A list of Fully Qualified Domain Names (FQDNs)
identifying resources under attack. An FQDN is the full name of a
resource, rather than just its hostname. For example, "venera" is
a hostname, and "venera.isi.edu" is an FQDN.
This is an optional attribute.
target-uri: A list of Uniform Resource Identifiers (URIs) [RFC3986]
identifying resources under attack.
This is an optional attribute.
alias-name: A list of aliases of resources for which the mitigation
is requested. Aliases can be created using the DOTS data channel
(Section 6.1 of [I-D.ietf-dots-data-channel]), direct
configuration, or other means. An alias is used in subsequent
signal channel exchanges to refer more efficiently to the
resources under attack.
This is an optional attribute.
lifetime: Lifetime of the mitigation request in seconds. The
RECOMMENDED lifetime of a mitigation request is 3600 seconds (60
minutes) -- this value was chosen to be long enough so that
refreshing is not typically a burden on the DOTS client, while
expiring the request where the client has unexpectedly quit in a
timely manner. DOTS clients MUST include this parameter in their
mitigation requests. Upon the expiry of this lifetime, and if the
request is not refreshed, the mitigation request is removed. The
request can be refreshed by sending the same request again.
A lifetime of 0 in a mitigation request is an invalid value.
A lifetime of negative one (-1) indicates indefinite lifetime for
the mitigation request. The DOTS server MAY refuse indefinite
lifetime, for policy reasons; the granted lifetime value is
returned in the response. DOTS clients MUST be prepared to not be
granted mitigations with indefinite lifetimes.
The DOTS server MUST always indicate the actual lifetime in the
response and the remaining lifetime in status messages sent to the
DOTS client.
This is a mandatory attribute.
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Because of the complexity to handle partial failure cases, this
specification does not allow for including multiple mitigation
requests in the same PUT request. Concretely, a DOTS client MUST NOT
include multiple 'scope' parameters in the same PUT request.
The CBOR key values for the parameters are defined in Section 6.
Section 9 defines how the CBOR key values can be allocated to
standard bodies and vendors.
FQDN and URI mitigation scopes may be thought of as a form of scope
alias, in which the addresses to which the domain name or URI resolve
represent the full scope of the mitigation.
In the PUT request at least one of the attributes 'target-prefix' or
'target-fqdn' or 'target-uri 'or 'alias-name' MUST be present. If
the attribute value is empty, then the attribute MUST NOT be present
in the request.
The relative order of two mitigation requests from a DOTS client is
determined by comparing their respective 'mitigation-id' values. If
two mitigation requests have overlapping mitigation scopes, the
mitigation request with the highest numeric 'mitigation-id' value
will override the other mitigation request. Two mitigation-ids from
a DOTS client are overlapping if there is a common IP address, IP
prefix, FQDN, URI, or alias-name. To avoid maintaining a long list
of overlapping mitigation requests from a DOTS client and avoid
error-prone provisioning of mitigation requests from a DOTS client,
the overlapped lower numeric 'mitigation-id' MUST be automatically
deleted and no longer available at the DOTS server.
The Uri-Path option carries a major and minor version nomenclature to
manage versioning and DOTS signal channel in this specification uses
v1 major version.
Figure 6 shows a PUT request example to signal that ports 80, 8080,
and 443 used by 2001:db8:6401::1 and 2001:db8:6401::2 servers are
under attack (illustrated in JSON diagnostic notation).
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Header: PUT (Code=0.03)
Uri-Host: "www.example.com"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "v1"
Uri-Path: "mitigate"
Content-Format: "application/cbor"
{
"mitigation-scope": {
"client-identifier": [
"dz6pHjaADkaFTbjr0JGBpw"
],
"scope": [
{
"mitigation-id": 12332,
"target-prefix": [
"2001:db8:6401::1/128",
"2001:db8:6401::2/128"
],
"target-port-range": [
{
"lower-port": 80
},
{
"lower-port": 443
},
{
"lower-port": 8080
}
],
"target-protocol": [
6
]
}
]
}
}
Figure 6: PUT for DOTS signal
The corresponding CBOR encoding format is shown in Figure 7.
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A1 # map(1)
01 # unsigned(1)
A2 # map(2)
18 20 # unsigned(32)
81 # array(1)
76 # text(22)
647A3670486A6141446B614654626A72304A47427077 # "dz6pHjaADkaFTbjr0JGBpw"
02 # unsigned(2)
81 # array(1)
A4 # map(4)
03 # unsigned(3)
19 302C # unsigned(12332)
04 # unsigned(4)
82 # array(2)
74 # text(20)
323030313A6462383A363430313A3A312F313238 # "2001:db8:6401::1/128"
74 # text(20)
323030313A6462383A363430313A3A322F313238 # "2001:db8:6401::2/128"
05 # unsigned(5)
83 # array(3)
A1 # map(1)
06 # unsigned(6)
18 50 # unsigned(80)
A1 # map(1)
06 # unsigned(6)
19 01BB # unsigned(443)
A1 # map(1)
06 # unsigned(6)
19 1F90 # unsigned(8080)
08 # unsigned(8)
81 # array(1)
06 # unsigned(6)
Figure 7: PUT for DOTS signal (CBOR)
If the DOTS client is using the certificate provisioned by the
Enrollment over Secure Transport (EST) server [RFC7030] in the DOTS
gateway-domain to authenticate itself to the DOTS gateway, then the
'client-identifier' value can be the output of a cryptographic hash
algorithm whose input is the DER-encoded ASN.1 representation of the
Subject Public Key Info (SPKI) of an X.509 certificate.
In this version of the specification, the cryptographic hash
algorithm used is SHA-256 [RFC6234]. The output of the cryptographic
hash algorithm is truncated to 16 bytes; truncation is done by
stripping off the final 16 bytes. The truncated output is base64url
encoded. If the 'client-identifier' value is already present in the
mitigation request received from the DOTS client, the DOTS gateway
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MAY compute the 'client-identifier' value, as discussed above, and
add the computed 'client-identifier' value to the end of the 'client-
identifier' list. The DOTS server MUST NOT use the 'client-
identifier' for the DOTS client authentication process.
In both DOTS signal and data channel sessions, the DOTS client MUST
authenticate itself to the DOTS server (Section 8). The DOTS server
may use the algorithm presented in Section 7 of [RFC7589] to derive
the DOTS client identity or username from the client certificate.
The DOTS client identity allows the DOTS server to accept mitigation
requests with scopes that the DOTS client is authorized to manage.
The DOTS server couples the DOTS signal and data channel sessions
using the DOTS client identity and the 'client-identifier' parameter
value, so the DOTS server can validate whether the aliases conveyed
in the mitigation request were indeed created by the same DOTS client
using the DOTS data channel session. If the aliases were not created
by the DOTS client, the DOTS server returns 4.00 (Bad Request) in the
response.
The DOTS server couples the DOTS signal channel sessions using the
DOTS client identity and the 'client-identifier' parameter value, and
the DOTS server uses 'mitigation-id' parameter value to detect
duplicate mitigation requests. If the mitigation request contains
the alias-name and other parameters identifying the target resources
(such as, 'target-prefix', 'target-port-range', 'target-fqdn', or
'target-uri'), then the DOTS server appends the parameter values in
'alias-name' with the corresponding parameter values in 'target-
prefix', 'target-port-range', 'target-fqdn', or 'target-uri'.
The DOTS server indicates the result of processing the PUT request
using CoAP response codes. CoAP 2.xx codes are success. CoAP 4.xx
codes are some sort of invalid requests (client errors). COAP 5.xx
codes are returned if the DOTS server has erred or is currently
unavailable to provide mitigation in response to the mitigation
request from the DOTS client.
Figure 8 shows an example of a PUT request that is successfully
processed (i.e., CoAP 2.xx response codes).
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{
"mitigation-scope": {
"client-identifier": [
"string"
],
"scope": [
{
"mitigation-id": 12332,
"lifetime": 3600
}
]
}
}
Figure 8: 2.xx response body
If the request is missing one or more mandatory attributes, or
includes multiple 'scope' parameters, or contains invalid or unknown
parameters, the DOTS server replies with 4.00 (Bad Request). DOTS
agents can safely ignore Vendor-Specific parameters they don't
understand.
A DOTS server that receives a mitigation request with a lifetime set
to '0' MUST reply with a 4.00 (Bad Request).
If the DOTS server does not find the 'mitigation-id' parameter value
conveyed in the PUT request in its configuration data, it MAY accept
the mitigation request by sending back a 2.01 (Created) response to
the DOTS client; the DOTS server will consequently try to mitigate
the attack.
If the DOTS server finds the 'mitigation-id' parameter value conveyed
in the PUT request in its configuration data, it MAY update the
mitigation request, and a 2.04 (Changed) response is returned to
indicate a successful update of the mitigation request.
If the request is conflicting with an existing mitigation request
from a different DOTS client, and the DOTS server decides to maintain
the conflicting mitigation request, the DOTS server returns 4.09
(Conflict) [RFC8132] to the requesting DOTS client. The response
includes enough information for a DOTS client to recognize the source
of the conflict (refer to 'conflict-information' specified in
Section 4.4.2).
For a mitigation request to continue beyond the initial negotiated
lifetime, the DOTS client has to refresh the current mitigation
request by sending a new PUT request. This PUT request MUST use the
same 'mitigation-id' value, and MUST repeat all the other parameters
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as sent in the original mitigation request apart from a possible
change to the lifetime parameter value.
A DOTS gateway MUST update the 'client-identifier' list in the
response to remove the 'client-identifier' value it had added in the
corresponding request before forwarding the response to the DOTS
client.
4.4.2. Retrieve Information Related to a Mitigation
A GET request is used by a DOTS client to retrieve information
(including status) of DOTS mitigations from a DOTS server.
The same considerations for manipulating 'client-identifier'
parameter by a DOTS gateway specified in Section 4.4.1 MUST be
followed for GET requests.
If the DOTS server does not find the 'mitigation-id' parameter value
conveyed in the GET request in its configuration data for the
requesting DOTS client or the one identified by 'client-identifier',
it MUST respond with a 4.04 (Not Found) error response code.
Likewise, the same error MUST be returned as a response to a request
to retrieve all mitigation records of a given DOTS client if the DOTS
server does not find any mitigation record for that DOTS client or
the one identified by 'client-identifier'.
The 'c' (content) parameter and its permitted values defined in
[I-D.ietf-core-comi] can be used to retrieve non-configuration data
(attack mitigation status) or configuration data or both. The DOTS
server may support this optional filtering capability. It can safely
ignore it if not supported.
The following examples illustrate how a DOTS client retrieves active
mitigation requests from a DOTS server. In particular:
o Figure 9 shows the example of a GET request to retrieve all DOTS
mitigation requests signaled by a DOTS client.
o Figure 10 shows the example of a GET request to retrieve a
specific DOTS mitigation request signaled by a DOTS client. The
configuration data to be reported in the response is formatted in
the same order it was processed by the DOTS server.
These two examples assume the default of "c=a"; that is, the DOTS
client asks for all data to be reported by the DOTS server.
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Header: GET (Code=0.01)
Uri-Host: "host"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "version"
Uri-Path: "mitigate"
Observe : 0
{
"mitigation-scope": {
"client-identifier": [
"dz6pHjaADkaFTbjr0JGBpw"
]
}
}
Figure 9: GET to retrieve all DOTS mitigation requests
Header: GET (Code=0.01)
Uri-Host: "host"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "version"
Uri-Path: "mitigate"
Observe : 0
Content-Format: "application/cbor"
{
"mitigation-scope": {
"client-identifier": [
"dz6pHjaADkaFTbjr0JGBpw"
],
"scope": [
{
"mitigation-id": 12332
}
]
}
}
Figure 10: GET to retrieve a specific DOTS mitigation request
Figure 11 shows a response example of all active mitigation requests
associated with the DOTS client on the DOTS server and the mitigation
status of each mitigation request.
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{
"mitigation-scope": {
"scope": [
{
"mitigation-id": 12332,
"mitigation-start": 1507818434.00,
"target-protocol": [
17
],
"lifetime": 1800,
"status": 2,
"bytes-dropped": 134334555,
"bps-dropped": 43344,
"pkts-dropped": 333334444,
"pps-dropped": 432432
},
{
"mitigation-id": 12333,
"mitigation-start": 1507818393.00,
"target-protocol": [
6
],
"lifetime": 1800,
"status": 3,
"bytes-dropped": 0,
"bps-dropped": 0,
"pkts-dropped": 0,
"pps-dropped": 0
}
]
}
}
Figure 11: Response body
The mitigation status parameters are described below:
mitigation-start: Mitigation start time is expressed in seconds
relative to 1970-01-01T00:00Z in UTC time (Section 2.4.1 of
[RFC7049]). The encoding is modified so that the leading tag 1
(epoch-based date/time) MUST be omitted.
This is a mandatory attribute.
lifetime: The remaining lifetime of the mitigation request, in
seconds.
This is a mandatory attribute.
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status: Status of attack mitigation. The various possible values of
'status' parameter are explained in Table 2.
This is a mandatory attribute.
conflict-information: Indicates that a mitigation request is
conflicting with another mitigation request(s) from other DOTS
client(s). This optional attribute has the following structure:
conflict-status: Indicates the status of a conflicting mitigation
request. The following values are defined:
1: DOTS server has detected conflicting mitigation requests
from different DOTS clients. This mitigation request is
currently inactive until the conflicts are resolved.
Another mitigation request is active.
2: DOTS server has detected conflicting mitigation requests
from different DOTS clients. This mitigation request is
currently active.
3: DOTS server has detected conflicting mitigation requests
from different DOTS clients. All conflicting mitigation
requests are inactive.
conflict-cause: Indicates the cause of the conflict. The
following values are defined:
1: Overlapping targets. 'conflict-scope' provides more details
about the conflicting target clauses.
2: Conflicts with an existing white list. This code is
returned when the DDoS mitigation detects source addresses/
prefixes in the white-listed ACLs are attacking the target.
conflict-scope Indicates the conflict scope. It may include a
list of IP addresses, a list of prefixes, a list of port
numbers, a list of target protocols, a list of FQDNs, a list of
URIs, a list of alias-names, or references to conflicting ACLs.
retry-timer Indicates, in seconds, the time after which the DOTS
client may re-issue the same request. The DOTS server returns
'retry-timer' only to DOTS client(s) for which a mitigation
request is deactivated. Any retransmission of the same
mitigation request before the expiry of this timer is likely to
be rejected by the DOTS server for the same reasons.
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The retry-timer SHOULD be equal to the lifetime of the active
mitigation request resulting in the deactivation of the
conflicting mitigation request. The lifetime of the
deactivated mitigation request will be updated to (retry-timer
+ 45 seconds), so the DOTS client can refresh the deactivated
mitigation request after retry-timer seconds before expiry of
lifetime and check if the conflict is resolved.
bytes-dropped: The total dropped byte count for the mitigation
request since the attack mitigation is triggered. The count wraps
around when it reaches the maximum value of unsigned integer.
This is an optional attribute.
bps-dropped: The average number of dropped bytes per second for the
mitigation request since the attack mitigation is triggered. This
SHOULD be a five-minute average.
This is an optional attribute.
pkts-dropped: The total number of dropped packet count for the
mitigation request since the attack mitigation is triggered.
This is an optional attribute.
pps-dropped: The average number of dropped packets per second for
the mitigation request since the attack mitigation is triggered.
This SHOULD be a five-minute average.
This is an optional attribute.
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+-----------+-------------------------------------------------------+
| Parameter | Description |
| value | |
+-----------+-------------------------------------------------------+
| 1 | Attack mitigation is in progress (e.g., changing the |
| | network path to re-route the inbound traffic to DOTS |
| | mitigator). |
+-----------+-------------------------------------------------------+
| 2 | Attack is successfully mitigated (e.g., traffic is |
| | redirected to a DDOS mitigator and attack traffic is |
| | dropped). |
+-----------+-------------------------------------------------------+
| 3 | Attack has stopped and the DOTS client can withdraw |
| | the mitigation request. |
+-----------+-------------------------------------------------------+
| 4 | Attack has exceeded the mitigation provider |
| | capability. |
+-----------+-------------------------------------------------------+
| 5 | DOTS client has withdrawn the mitigation request and |
| | the mitigation is active but terminating. |
+-----------+-------------------------------------------------------+
| 6 | Attack mitigation is now terminated. |
+-----------+-------------------------------------------------------+
| 7 | Attack mitigation is withdrawn. |
+-----------+-------------------------------------------------------+
| 8 | Attack mitigation is rejected. |
+-----------+-------------------------------------------------------+
Table 2: Values of 'status' parameter
The observe option defined in [RFC7641] extends the CoAP core
protocol with a mechanism for a CoAP client to "observe" a resource
on a CoAP server: The client retrieves a representation of the
resource and requests this representation be updated by the server as
long as the client is interested in the resource. A DOTS client
conveys the observe option set to '0' in the GET request to receive
unsolicited notifications of attack mitigation status from the DOTS
server.
Unidirectional notifications within the bidirectional signal channel
allows unsolicited message delivery, enabling asynchronous
notifications between the agents. Due to the higher likelihood of
packet loss during a DDoS attack, DOTS server periodically sends
attack mitigation status to the DOTS client and also notifies the
DOTS client whenever the status of the attack mitigation changes. If
the DOTS server cannot maintain a RTT estimate, it SHOULD NOT send
more than one unsolicited notification every 3 seconds, and SHOULD
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use an even less aggressive rate whenever possible (case 2 in
Section 3.1.3 of [RFC8085]).
When conflicting requests are detected, the DOTS server enforces the
corresponding policy (e.g., accept all requests, reject all requests,
accept only one request but reject all the others, ...). It is
assumed that this policy is supplied by the DOTS server administrator
or it is a default behavior of the DOTS server implementation. Then,
the DOTS server sends notification message(s) to the DOTS client(s)
at the origin of the conflict. A conflict notification message
includes information about the conflict cause, scope, and the status
of the mitigation request(s). For example,
o A notification message with status code set to '8 (Attack
mitigation is rejected)' and 'conflict-status' set to '1' is sent
to a DOTS client to indicate that this mitigation request is
rejected because a conflict is detected.
o A notification message with status code set to '7 (Attack
mitigation is withdrawn)' and 'conflict-status' set to '1' is sent
to a DOTS client to indicate that an active mitigation request is
deactivated because a conflict is detected.
o A notification message with status code set to '1 (Attack
mitigation is in progress)' and 'conflict-status' set to '2' is
sent to a DOTS client to indicate that this mitigation request is
in progress, but a conflict is detected.
Upon receipt of a conflict notification message indicating that a
mitigation request is deactivated because of a conflict, a DOTS
client MUST NOT resend the same mitigation request before the expiry
of 'retry-timer'. It is also recommended that DOTS clients support
means to alert administrators about mitigation conflicts.
A DOTS client that is no longer interested in receiving notifications
from the DOTS server can simply "forget" the observation. When the
DOTS server sends the next notification, the DOTS client will not
recognize the token in the message and thus will return a Reset
message. This causes the DOTS server to remove the associated entry.
Alternatively, the DOTS client can explicitly deregister itself by
issuing a GET request that has the Token field set to the token of
the observation to be cancelled and includes an Observe Option with
the value set to '1' (deregister).
Figure 12 shows an example of a DOTS client requesting a DOTS server
to send notifications related to a given mitigation request.
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DOTS Client DOTS Server
| |
| GET /<mitigation-id number> |
| Token: 0x4a | Registration
| Observe: 0 |
+------------------------------>|
| |
| 2.05 Content |
| Token: 0x4a | Notification of
| Observe: 12 | the current state
| status: "mitigation |
| in progress" |
|<------------------------------+
| 2.05 Content |
| Token: 0x4a | Notification upon
| Observe: 44 | a state change
| status: "mitigation |
| complete" |
|<------------------------------+
| 2.05 Content |
| Token: 0x4a | Notification upon
| Observe: 60 | a state change
| status: "attack stopped" |
|<------------------------------+
| |
Figure 12: Notifications of attack mitigation status
4.4.2.1. Mitigation Status
The DOTS client can send the GET request at frequent intervals
without the Observe option to retrieve the configuration data of the
mitigation request and non-configuration data (i.e., the attack
status). The frequency of polling the DOTS server to get the
mitigation status should follow the transmission guidelines given in
Section 3.1.3 of [RFC8085]. If the DOTS server has been able to
mitigate the attack and the attack has stopped, the DOTS server
indicates as such in the status, and the DOTS client recalls the
mitigation request by issuing a DELETE request for the mitigation-id.
A DOTS client SHOULD react to the status of the attack as per the
information sent by the DOTS server rather than acknowledging by
itself, using its own means, that the attack has been mitigated.
This ensures that the DOTS client does not recall a mitigation
request prematurely because it is possible that the DOTS client does
not sense the DDOS attack on its resources but the DOTS server could
be actively mitigating the attack and the attack is not completely
averted.
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4.4.3. Efficacy Update from DOTS Clients
While DDoS mitigation is active, due to the likelihood of packet
loss, a DOTS client MAY periodically transmit DOTS mitigation
efficacy updates to the relevant DOTS server. A PUT request is used
to convey the mitigation efficacy update to the DOTS server.
The PUT request MUST include all the parameters used in the PUT
request to carry the DOTS signal (Section 4.4.1) unchanged apart from
the lifetime parameter value. If this is not the case, the DOTS
server MUST reject the request with a 4.00 (Bad Request).
The If-Match Option (Section 5.10.8.1 of [RFC7252]) with an empty
value is used to make the PUT request conditional on the current
existence of the mitigation request. If UDP is used as transport,
CoAP requests may arrive out-of-order. For example, the DOTS client
may send a PUT request to convey an efficacy update to the DOTS
server followed by a DELETE request to withdraw the mitigation
request, but the DELETE request arrives at the DOTS server before the
PUT request. To handle out-of-order delivery of requests, if an If-
Match option is present in the PUT request and the 'mitigation-id' in
the request matches a mitigation request from that DOTS client, then
the request is processed. If no match is found, the PUT request is
silently ignored.
An example of an efficacy update message, which includes an If-Match
option with an empty value, is depicted in Figure 13.
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Header: PUT (Code=0.03)
Uri-Host: "host"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "version"
Uri-Path: "mitigate"
Content-Format: "application/cbor"
If-Match:
{
"mitigation-scope": {
"client-identifier": [
"string"
],
"scope": [
{
"mitigation-id": integer,
"target-prefix": [
"string"
],
"target-port-range": [
{
"lower-port": integer,
"upper-port": integer
}
],
"target-protocol": [
integer
],
"target-fqdn": [
"string"
],
"target-uri": [
"string"
],
"alias-name": [
"string"
],
"lifetime": integer,
"attack-status": integer
}
]
}
}
Figure 13: Efficacy Update
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The 'attack-status' parameter is a mandatory attribute when
performing an efficacy update. The various possible values contained
in the 'attack-status' parameter are described in Table 3.
+-----------+-------------------------------------------------------+
| Parameter | Description |
| value | |
+-----------+-------------------------------------------------------+
| 1 | The DOTS client determines that it is still under |
| | attack. |
+-----------+-------------------------------------------------------+
| 2 | The DOTS client determines that the attack is |
| | successfully mitigated (e.g., attack traffic is not |
| | seen). |
+-----------+-------------------------------------------------------+
Table 3: Values of 'attack-status' parameter
The DOTS server indicates the result of processing a PUT request
using CoAP response codes. The response code 2.04 (Changed) is
returned if the DOTS server has accepted the mitigation efficacy
update. The error response code 5.03 (Service Unavailable) is
returned if the DOTS server has erred or is incapable of performing
the mitigation.
4.4.4. Withdraw a Mitigation
A DELETE request is used to withdraw a DOTS mitigation request from a
DOTS server (Figure 14).
The same considerations for manipulating 'client-identifier'
parameter by a DOTS gateway, as specified in Section 4.4.1, MUST be
followed for DELETE requests.
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Header: DELETE (Code=0.04)
Uri-Host: "host"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "version"
Uri-Path: "mitigate"
Content-Format: "application/cbor"
{
"mitigation-scope": {
"client-identifier": [
"string"
],
"scope": [
{
"mitigation-id": integer
}
]
}
}
Figure 14: Withdraw DOTS signal
If the request does not include a 'mitigation-id' parameter, the DOTS
server MUST reply with a 4.00 (Bad Request).
Once the request is validated, the DOTS server immediately
acknowledges a DOTS client's request to withdraw the DOTS signal
using 2.02 (Deleted) response code with no response payload. A 2.02
(Deleted) Response Code is returned even if the 'mitigation-id'
parameter value conveyed in the DELETE request does not exist in its
configuration data before the request.
If the DOTS server finds the 'mitigation-id' parameter value conveyed
in the DELETE request in its configuration data for the DOTS client,
then to protect against route or DNS flapping caused by a DOTS client
rapidly removing a mitigation, and to dampen the effect of
oscillating attacks, the DOTS server MAY allow mitigation to continue
for a limited period after acknowledging a DOTS client's withdrawal
of a mitigation request. During this period, the DOTS server status
messages SHOULD indicate that mitigation is active but terminating
(Section 4.4.2).
The initial active-but-terminating period SHOULD be sufficiently long
to absorb latency incurred by route propagation. The active-but-
terminating period SHOULD be set by default to 120 seconds. If the
client requests mitigation again before the initial active-but-
terminating period elapses, the DOTS server MAY exponentially
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increase the active-but- terminating period up to a maximum of 300
seconds (5 minutes).
After the active-but-terminating period elapses, the DOTS server MUST
treat the mitigation as terminated, as the DOTS client is no longer
responsible for the mitigation. For example, if there is a financial
relationship between the DOTS client and server domains, the DOTS
client stops incurring cost at this point.
4.5. DOTS Signal Channel Session Configuration
The DOTS client can negotiate, configure, and retrieve the DOTS
signal channel session behavior. The DOTS signal channel can be
used, for example, to configure the following:
a. Heartbeat interval (heartbeat-interval): DOTS agents regularly
send heartbeats (CoAP Ping/Pong) to each other after mutual
authentication is successfully completed in order to keep the
DOTS signal channel open. Heartbeat messages are exchanged
between the DOTS agents every 'heartbeat-interval' seconds to
detect the current status of the DOTS signal channel session.
b. Missing heartbeats allowed (missing-hb-allowed): This variable
indicates the maximum number of consecutive heartbeat messages
for which a DOTS agent did not receive a response before
concluding that the session is disconnected or defunct.
c. Acceptable signal loss ratio: Maximum retransmissions,
retransmission timeout value, and other message transmission
parameters for the DOTS signal channel.
Requests and responses are deemed reliable by marking them as
Confirmable (CON) messages. DOTS signal channel session
configuration requests and responses are marked as Confirmable
messages. As explained in Section 2.1 of [RFC7252], a Confirmable
message is retransmitted using a default timeout and exponential
back-off between retransmissions, until the DOTS server sends an
Acknowledgement message (ACK) with the same Message ID conveyed from
the DOTS client.
Message transmission parameters are defined in Section 4.8 of
[RFC7252]. The DOTS server can either piggyback the response in the
acknowledgement message or, if the DOTS server cannot respond
immediately to a request carried in a Confirmable message, it simply
responds with an Empty Acknowledgement message so that the DOTS
client can stop retransmitting the request. Empty Acknowledgement
message is explained in Section 2.2 of [RFC7252]. When the response
is ready, the server sends it in a new Confirmable message which in
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turn needs to be acknowledged by the DOTS client (see Sections 5.2.1
and 5.2.2 of [RFC7252]). Requests and responses exchanged between
DOTS agents during peacetime are marked as Confirmable messages.
Implementation Note: A DOTS client that receives a response in a
CON message may want to clean up the message state right after
sending the ACK. If that ACK is lost and the DOTS server
retransmits the CON, the DOTS client may no longer have any state
that would help it correlate this response, thereby unexpecting
the retransmission message. The DOTS client will send a Reset
message so it does not receive any more retransmissions. This
behavior is normal and not an indication of an error (see
Section 5.3.2 of [RFC7252] for more details).
4.5.1. Discover Configuration Parameters
A GET request is used to obtain acceptable (e.g., minimum and maximum
values) and current configuration parameters on the DOTS server for
DOTS signal channel session configuration. Figure 15 shows how to
obtain acceptable configuration parameters for the DOTS server.
Header: GET (Code=0.01)
Uri-Host: "host"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "version"
Uri-Path: "config"
Figure 15: GET to retrieve configuration
The DOTS server in the 2.05 (Content) response conveys the current,
minimum, and maximum attribute values acceptable by the DOTS server
(Figure 16).
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Content-Format: "application/cbor"
{
"heartbeat-interval": {
"current-value": integer,
"min-value": integer,
"max-value": integer
},
"missing-hb-allowed": {
"current-value": integer,
"min-value": integer,
"max-value": integer
},
"max-retransmit": {
"current-value": integer,
"min-value": integer,
"max-value": integer
},
"ack-timeout": {
"current-value": integer,
"min-value": integer,
"max-value": integer
},
"ack-random-factor": {
"current-value": number,
"min-value": number,
"max-value": number
},
"trigger-mitigation": {
"current-value": boolean
},
"config-interval": {
"current-value": integer,
"min-value": integer,
"max-value": integer
}
}
Figure 16: GET response body
Figure 17 shows an example of acceptable and current configuration
parameters on a DOTS server for DOTS signal channel session
configuration.
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Content-Format: "application/cbor"
{
"heartbeat-interval": {
"current-value": 30,
"min-value": 15,
"max-value": 240
},
"missing-hb-allowed": {
"current-value": 5,
"min-value": 3,
"max-value": 9
},
"max-retransmit": {
"current-value": 3,
"min-value": 2,
"max-value": 15
},
"ack-timeout": {
"current-value": 2,
"min-value": 1,
"max-value": 30
},
"ack-random-factor": {
"current-value": 1.5,
"min-value": 1.1,
"max-value": 4.0
},
"trigger-mitigation": {
"current-value": true
},
"config-interval": {
"current-value": 1439,
"min-value": 0,
"max-value": 65535
}
}
Figure 17: Configuration response body
4.5.2. Convey DOTS Signal Channel Session Configuration
A PUT request is used to convey the configuration parameters for the
signal channel (e.g., heartbeat interval, maximum retransmissions).
Message transmission parameters for CoAP are defined in Section 4.8
of [RFC7252]. The RECOMMENDED values of transmission parameter
values are ack-timeout (2 seconds), max-retransmit (3), ack-random-
factor (1.5). In addition to those parameters, the RECOMMENDED
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specific DOTS transmission parameter values are heartbeat-interval
(30 seconds) and missing-hb-allowed (5).
Note: heartbeat-interval should be tweaked to also assist DOTS
messages for NAT traversal (SIG-010 of
[I-D.ietf-dots-requirements]). According to [RFC8085], keepalive
messages must not be sent more frequently than once every 15
seconds and should use longer intervals when possible.
Furthermore, [RFC4787] recommends NATs to use a state timeout of 2
minutes or longer, but experience shows that sending packets every
15 to 30 seconds is necessary to prevent the majority of
middleboxes from losing state for UDP flows. From that
standpoint, this specification recommends a minimum heartbeat-
interval of 15 seconds and a maximum heartbeat-interval of 240
seconds. The recommended value of 30 seconds is selected to
anticipate the expiry of NAT state.
A heartbeat-interval of 30 seconds may be seen as too chatty in
some deployments. For such deployments, DOTS agents may negotiate
longer heartbeat-interval values to prevent any network overload
with too frequent keepalives.
When a confirmable "CoAP Ping" is sent, and if there is no response,
the "CoAP Ping" is retransmitted max-retransmit number of times by
the CoAP layer using an initial timeout set to a random duration
between ack-timeout and (ack-timeout*ack-random-factor) and
exponential back-off between retransmissions. By choosing the
recommended transmission parameters, the "CoAP Ping" will timeout
after 45 seconds. If the DOTS agent does not receive any response
from the peer DOTS agent for 'missing-hb-allowed' number of
consecutive "CoAP Ping" confirmable messages, it concludes that the
DOTS signal channel session is disconnected. A DOTS client MUST NOT
transmit a "CoAP Ping" while waiting for the previous "CoAP Ping"
response from the same DOTS server.
If the DOTS agent wishes to change the default values of message
transmission parameters, then it should follow the guidance given in
Section 4.8.1 of [RFC7252]. The DOTS agents MUST use the negotiated
values for message transmission parameters and default values for
non-negotiated message transmission parameters.
The signal channel session configuration is applicable to a single
DOTS signal channel session between the DOTS agents.
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Header: PUT (Code=0.03)
Uri-Host: "host"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "version"
Uri-Path: "config"
Content-Format: "application/cbor"
{
"signal-config": {
"session-id": integer,
"heartbeat-interval": integer,
"missing-hb-allowed": integer,
"max-retransmit": integer,
"ack-timeout": integer,
"ack-random-factor": number,
"trigger-mitigation": boolean,
"config-interval": integer
}
}
Figure 18: PUT to convey the DOTS signal channel session
configuration data.
The parameters in Figure 18 are described below:
session-id: Identifier for the DOTS signal channel session
configuration data represented as an integer. This identifier
MUST be generated by the DOTS client. This document does not make
any assumption about how this identifier is generated.
This is a mandatory attribute.
heartbeat-interval: Time interval in seconds between two
consecutive heartbeat messages.
'0' is used to disable the heartbeat mechanism.
This is an optional attribute.
missing-hb-allowed: Maximum number of consecutive heartbeat
messages for which the DOTS agent did not receive a response
before concluding that the session is disconnected.
This is an optional attribute.
max-retransmit: Maximum number of retransmissions for a message
(referred to as MAX_RETRANSMIT parameter in CoAP).
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This is an optional attribute.
ack-timeout: Timeout value in seconds used to calculate the initial
retransmission timeout value (referred to as ACK_TIMEOUT parameter
in CoAP).
This is an optional attribute.
ack-random-factor: Random factor used to influence the timing of
retransmissions (referred to as ACK_RANDOM_FACTOR parameter in
CoAP).
This is an optional attribute.
trigger-mitigation: If the parameter value is set to 'false', then
DDoS mitigation is triggered only when the DOTS signal channel
session is lost. Automated mitigation on loss of signal is
discussed in Section 3.3.3 of [I-D.ietf-dots-architecture].
If the DOTS client ceases to respond to heartbeat messages, the
DOTS server can detect that the DOTS session is lost.
The default value of the parameter is 'true'.
This is an optional attribute.
config-interval: This parameter is returned to indicate the time
interval expressed in minutes, which a DOTS agent must wait for
before re-contacting its peer in order to retrieve the signal
channel configuration data.
'0' is used to disable this refresh mechanism.
If a non-null value of 'config-interval' is received by a DOTS
agent, it has to issue a PUT request to refresh the configuration
parameters for the signal channel before the expiry of 'config-
interval'.
This mechanism allows to update the configuration data if a change
occurs at the DOTS server side. For example, the new
configuration may instruct a DOTS client to cease heartbeats or
reduce heartbeat frequency.
If this parameter is not returned, this is equivalent to receiving
a 'config-interval' value set to '0'.
If a DOTS server detects that a misbehaving DOTS client does not
contact the DOTS server after the expiry of 'config-interval', in
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order to retrieve the signal channel configuration data, it MAY
terminate the (D)TLS session. A (D)TLS session is terminated by
the receipt of an authenticated message that closes the connection
(e.g., a fatal alert (Section 7.2 of [RFC5246])).
This is an optional attribute.
At least one of the attributes 'heartbeat-interval', 'missing-hb-
allowed', 'max-retransmit', 'ack-timeout', 'ack-random-factor', and
'trigger-mitigation' MUST be present in the PUT request . The PUT
request with a higher numeric 'session-id' value overrides the DOTS
signal channel session configuration data installed by a PUT request
with a lower numeric 'session-id' value.
Figure 19 shows a PUT request example to convey the configuration
parameters for the DOTS signal channel.
Header: PUT (Code=0.03)
Uri-Host: "www.example.com"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "v1"
Uri-Path: "config"
Content-Format: "application/cbor"
{
"signal-config": {
"session-id": 1234534333242,
"heartbeat-interval": 91,
"missing-hb-allowed": 3,
"max-retransmit": 7,
"ack-timeout": 5,
"ack-random-factor": 1.5,
"trigger-mitigation": false
}
}
Figure 19: PUT to convey the configuration parameters
The DOTS server indicates the result of processing the PUT request
using CoAP response codes:
o If the DOTS server finds the 'session-id' parameter value conveyed
in the PUT request in its configuration data and if the DOTS
server has accepted the updated configuration parameters, then
2.04 (Changed) code is returned in the response.
o If the DOTS server does not find the 'session-id' parameter value
conveyed in the PUT request in its configuration data and if the
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DOTS server has accepted the configuration parameters, then a
response code 2.01 (Created) is returned in the response.
o If the request is missing one or more mandatory attributes or it
contains one or more invalid or unknown parameters, then 4.00 (Bad
Request) is returned in the response.
o Response code 4.22 (Unprocessable Entity) is returned in the
response, if any of the 'heartbeat-interval', 'missing-hb-
allowed', 'max-retransmit', 'target-protocol', 'ack-timeout', and
'ack-random-factor' attribute values are not acceptable to the
DOTS server. Upon receipt of the 4.22 error response code, the
DOTS client should request the maximum and minimum attribute
values acceptable to the DOTS server (Section 4.5.1).
The DOTS client may re-try and send the PUT request with updated
attribute values acceptable to the DOTS server.
4.5.3. Delete DOTS Signal Channel Session Configuration
A DELETE request is used to delete the installed DOTS signal channel
session configuration data (Figure 20).
Header: DELETE (Code=0.04)
Uri-Host: "host"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "version"
Uri-Path: "config"
Content-Format: "application/cbor"
Figure 20: DELETE configuration
The DOTS server resets the DOTS signal channel session configuration
back to the default values and acknowledges a DOTS client's request
to remove the DOTS signal channel session configuration using 2.02
(Deleted) response code.
4.6. Redirected Signaling
Redirected DOTS signaling is discussed in detail in Section 3.2.2 of
[I-D.ietf-dots-architecture].
If a DOTS server wants to redirect a DOTS client to an alternative
DOTS server for a signal session, then the response code 3.00
(alternate server) will be returned in the response to the client.
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The DOTS server can return the error response code 3.00 in response
to a PUT request from the DOTS client or convey the error response
code 3.00 in a unidirectional notification response from the DOTS
server.
The DOTS server in the error response conveys the alternate DOTS
server's FQDN, and the alternate DOTS server's IP address(es) and
time to live values in the CBOR body (Figure 21).
{
"alt-server": "string",
"alt-server-record": [
{
"addr": "string",
"ttl" : integer
}
]
}
Figure 21: Error response body
The parameters are described below:
alt-server: FQDN of an alternate DOTS server.
addr: IP address of an alternate DOTS server.
ttl: Time to live (TTL) represented as an integer number of seconds.
Figure 22 shows a 3.00 response example to convey the DOTS alternate
server 'alt-server.example', its IP addresses 2001:db8:6401::1 and
2001:db8:6401::2, and TTL values 3600 and 1800.
{
"alt-server": "alt-server.example",
"alt-server-record": [
{
"ttl" : 3600,
"addr": "2001:db8:6401::1"
},
{
"ttl" : 1800,
"addr": "2001:db8:6401::2"
}
]
}
Figure 22: Example of error response body
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When the DOTS client receives 3.00 response, it considers the current
request as failed, but SHOULD try re-sending the request to the
alternate DOTS server. During a DDOS attack, the DNS server may be
the target of another DDoS attack, alternate DOTS server's IP
addresses conveyed in the 3.00 response help the DOTS client skip DNS
lookup of the alternate DOTS server. The DOTS client can then try to
establish a UDP or a TCP session with the alternate DOTS server. The
DOTS client SHOULD implement a DNS64 function to handle the scenario
where an IPv6-only DOTS client communicates with an IPv4-only
alternate DOTS server.
4.7. Heartbeat Mechanism
To provide an indication of signal health and distinguish an 'idle'
signal channel from a 'disconnected' or 'defunct' session, the DOTS
agent sends a heartbeat over the signal channel to maintain its half
of the channel. The DOTS agent similarly expects a heartbeat from
its peer DOTS agent, and may consider a session terminated in the
prolonged absence of a peer agent heartbeat.
While the communication between the DOTS agents is quiescent, the
DOTS client will probe the DOTS server to ensure it has maintained
cryptographic state and vice versa. Such probes can also keep
firewall and/or NAT bindings alive. This probing reduces the
frequency of establishing a new handshake when a DOTS signal needs to
be conveyed to the DOTS server.
In case of a massive DDoS attack that saturates the incoming link(s)
to the DOTS client, all traffic from the DOTS server to the DOTS
client will likely be dropped, although the DOTS server receives
heartbeat requests in addition to DOTS messages sent by the DOTS
client. In this scenario, the DOTS agents MUST behave differently to
handle message transmission and DOTS session liveliness during link
saturation:
o The DOTS client MUST NOT consider the DOTS session terminated even
after a maximum 'missing-hb-allowed' threshold is reached. The
DOTS client SHOULD keep on using the current DOTS session to send
heartbeat requests over it, so that the DOTS server knows the DOTS
client has not disconnected the DOTS session.
After the maximum 'missing-hb-allowed' threshold is reached, the
DOTS client SHOULD try to resume the (D)TLS session. The DOTS
client SHOULD send mitigation requests over the current DOTS
session, and in parallel, for example, try to resume the (D)TLS
session or use 0-RTT mode in DTLS 1.3 to piggyback the mitigation
request in the ClientHello message.
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As soon as the link is no longer saturated, if traffic from the
DOTS server reaches the DOTS client over the current DOTS session,
the DOTS client can stop (D)TLS session resumption or if (D)TLS
session resumption is successful then disconnect the current DOTS
session.
o If the DOTS server does not receive any traffic from the peer DOTS
client, then the DOTS server sends heartbeat requests to the DOTS
client and after maximum 'missing-hb-allowed' threshold is
reached, the DOTS server concludes the session is disconnected.
In DOTS over UDP, heartbeat messages MUST be exchanged between the
DOTS agents using the "CoAP Ping" mechanism defined in Section 4.2 of
[RFC7252]. Concretely, the DOTS agent sends an Empty Confirmable
message and the peer DOTS agent will respond by sending a Reset
message.
In DOTS over TCP, heartbeat messages MUST be exchanged between the
DOTS agents using the Ping and Pong messages specified in Section 4.4
of [I-D.ietf-core-coap-tcp-tls]. That is, the DOTS agent sends a
Ping message and the peer DOTS agent would respond by sending a
single Pong message.
5. DOTS Signal Channel YANG Module
This document defines a YANG [RFC7950] module for mitigation scope
and DOTS signal channel session configuration data.
5.1. Tree Structure
This document defines the YANG module "ietf-dots-signal"
(Section 5.2), which has the following tree structure. A DOTS signal
message can either be a mitigation or a configuration message.
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module: ietf-dots-signal
+--rw dots-signal
+--rw (message-type)?
+--:(mitigation-scope)
| +--rw client-identifier* binary
| +--rw scope* [mitigation-id]
| +--rw mitigation-id int32
| +--rw target-prefix* inet:ip-prefix
| +--rw target-port-range* [lower-port upper-port]
| | +--rw lower-port inet:port-number
| | +--rw upper-port inet:port-number
| +--rw target-protocol* uint8
| +--rw target-fqdn* inet:domain-name
| +--rw target-uri* inet:uri
| +--rw alias-name* string
| +--rw lifetime? int32
| +--rw mitigation-start? int64
| +--ro status? enumeration
| +--ro conflict-information
| | +--ro conflict-status? enumeration
| | +--ro conflict-cause? enumeration
| | +--ro retry-timer? int32
| | +--ro conflict-scope
| | +--ro target-prefix* inet:ip-prefix
| | +--ro target-port-range* [lower-port upper-port]
| | | +--ro lower-port inet:port-number
| | | +--ro upper-port inet:port-number
| | +--ro target-protocol* uint8
| | +--ro target-fqdn* inet:domain-name
| | +--ro target-uri* inet:uri
| | +--ro alias-name* string
| | +--ro acl-list* [acl-name acl-type]
| | +--ro acl-name -> /ietf-acl:access-lists/acl/acl-name
| | +--ro acl-type -> /ietf-acl:access-lists/acl/acl-type
| +--ro pkts-dropped? yang:zero-based-counter64
| +--ro bps-dropped? yang:zero-based-counter64
| +--ro bytes-dropped? yang:zero-based-counter64
| +--ro pps-dropped? yang:zero-based-counter64
+--:(configuration)
+--rw session-id int32
+--rw heartbeat-interval? int16
+--rw missing-hb-allowed? int16
+--rw max-retransmit? int16
+--rw ack-timeout? int16
+--rw ack-random-factor? decimal64
+--rw trigger-mitigation? boolean
+--rw config-interval? int32
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5.2. YANG Module
<CODE BEGINS> file "ietf-dots-signal@2017-12-12.yang"
module ietf-dots-signal {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-dots-signal";
prefix "signal";
import ietf-inet-types {prefix "inet";}
import ietf-yang-types {prefix yang;}
import ietf-access-control-list {prefix "ietf-acl";}
organization "IETF DDoS Open Threat Signaling (DOTS) Working Group";
contact
"Konda, Tirumaleswar Reddy <TirumaleswarReddy_Konda@McAfee.com>
Mohamed Boucadair <mohamed.boucadair@orange.com>
Prashanth Patil <praspati@cisco.com>
Andrew Mortensen <amortensen@arbor.net>
Nik Teague <nteague@verisign.com>";
description
"This module contains YANG definition for the signaling
messages exchanged between a DOTS client and a DOTS server.
Copyright (c) 2017 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see
the RFC itself for full legal notices.";
revision 2017-12-12 {
description
"Initial revision.";
reference
"RFC XXXX: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel";
}
grouping target {
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description
"Specifies the scope of the mitigation request.";
leaf-list target-prefix {
type inet:ip-prefix;
description
"IPv4 or IPv6 prefix identifying the target.";
}
list target-port-range {
key "lower-port upper-port";
description
"Port range. When only lower-port is
present, it represents a single port.";
leaf lower-port {
type inet:port-number;
mandatory true;
description "Lower port number.";
}
leaf upper-port {
type inet:port-number;
must ". >= ../lower-port" {
error-message
"The upper port number must be greater than
or equal to lower port number.";
}
description "Upper port number.";
}
}
leaf-list target-protocol {
type uint8;
description
"Identifies the target protocol number.
The value '0' means 'all protocols'.
Values are taken from the IANA protocol registry:
https://www.iana.org/assignments/protocol-numbers/
protocol-numbers.xhtml
For example, 6 for TCP or 17 for UDP.";
}
leaf-list target-fqdn {
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type inet:domain-name;
description "FQDN identifying the target.";
}
leaf-list target-uri {
type inet:uri;
description "URI identifying the target.";
}
leaf-list alias-name {
type string;
description "alias name";
}
}
grouping mitigation-scope {
description
"Specifies the scope of the mitigation request.";
leaf-list client-identifier {
type binary;
description
"The client identifier may be conveyed by
the DOTS gateway to propagate the DOTS client
identification information from the gateway's client-side to the
gateway's server-side, and from the gateway's
server-side to the DOTS server.
It allows the destination DOTS server to accept
mitigation requests with scopes which the DOTS
client is authorized to manage.";
}
list scope {
key mitigation-id;
description
"The scope of the request.";
leaf mitigation-id {
type int32;
description
"Mitigation request identifier.
This identifier must be unique for each mitigation
request bound to the DOTS client.";
}
uses target;
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leaf lifetime {
type int32;
units "seconds";
default 3600;
description
"Indicates the lifetime of the mitigation request.";
reference
"RFC XXXX: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel";
}
leaf mitigation-start {
type int64;
units "seconds";
description
"Mitigation start time is represented in seconds
relative to 1970-01-01T00:00Z in UTC time.";
}
leaf status {
type enumeration {
enum "attack-mitigation-in-progress" {
value 1;
description
"Attack mitigation is in progress (e.g., changing
the network path to re-route the inbound traffic
to DOTS mitigator).";
}
enum "attack-successfully-mitigated" {
value 2;
description
"Attack is successfully mitigated (e.g., traffic
is redirected to a DDOS mitigator and attack
traffic is dropped or blackholed).";
}
enum "attack-stopped" {
value 3;
description
"Attack has stopped and the DOTS client can
withdraw the mitigation request.";
}
enum "attack-exceeded-capability" {
value 4;
description
"Attack has exceeded the mitigation provider
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capability.";
}
enum "dots-client-withdrawn-mitigation" {
value 5;
description
"DOTS client has withdrawn the mitigation
request and the mitigation is active but
terminating.";
}
enum "attack-mitigation-terminated" {
value 6;
description
"Attack mitigation is now terminated.";
}
enum "attack-mitigation-withdrawn" {
value 7;
description
"Attack mitigation is withdrawn.";
}
enum "attack-mitigation-rejected" {
value 8;
description
"Attack mitigation is rejected.";
}
}
config false;
description
"Indicates the status of a mitigation request.
It must be included in responses only.";
}
container conflict-information {
config false;
description
"Indicates that a conflict is detected.
Must only be used for responses.";
leaf conflict-status {
type enumeration {
enum "request-inactive-other-active" {
value 1;
description
"DOTS Server has detected conflicting mitigation
requests from different DOTS clients.
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This mitigation request is currently inactive
until the conflicts are resolved. Another
mitigation request is active.";
}
enum "request-active" {
value 2;
description
"DOTS Server has detected conflicting mitigation
requests from different DOTS clients.
This mitigation request is currently active.";
}
enum "all-requests-inactive" {
value 3;
description
"DOTS Server has detected conflicting mitigation
requests from different DOTS clients. All
conflicting mitigation requests are inactive.";
}
}
description
"Indicates the conflict status.
It must be included in responses only.";
}
leaf conflict-cause {
type enumeration {
enum "overlapping-targets" {
value 1;
description
"Overlapping targets. conflict-scope provides
more details about the exact conflict.";
}
enum "conflict-with-whitelist" {
value 2;
description
"Conflicts with an existing white list.
This code is returned when the DDoS mitigation
detects that some of the source addresses/prefixes
listed in the white list ACLs are actually
attacking the target.";
}
}
description
"Indicates the cause of the conflict.
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It must be included in responses only.";
}
leaf retry-timer {
type int32;
units "seconds";
description
"The DOTS client must not re-send the
same request before the expiry of this timer.
It must be included in responses, only.";
}
container conflict-scope {
description
"Provides more information about the conflict scope.";
uses target {
when "../conflict-cause = 'overlapping-targets'";
}
list acl-list {
when "../../conflict-cause = 'conflict-with-whitelist'";
key "acl-name acl-type";
description
"List of conflicting ACLs";
leaf acl-name {
type leafref {
path "/ietf-acl:access-lists/ietf-acl:acl" +
"/ietf-acl:acl-name";
}
description
"Reference to the conflicting ACL name bound to
a DOTS client.";
}
leaf acl-type {
type leafref {
path "/ietf-acl:access-lists/ietf-acl:acl" +
"/ietf-acl:acl-type";
}
description
"Reference to the conflicting ACL type bound to
a DOTS client.";
}
}
}
}
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leaf pkts-dropped {
type yang:zero-based-counter64;
config false;
description
"Number of dropped packets";
}
leaf bps-dropped {
type yang:zero-based-counter64;
config false;
description
"The average number of dropped bytes per second for
the mitigation request since the attack
mitigation is triggered.";
}
leaf bytes-dropped {
type yang:zero-based-counter64;
units 'bytes';
config false;
description
"Counter for dropped packets; in bytes.";
}
leaf pps-dropped {
type yang:zero-based-counter64;
config false;
description
"The average number of dropped packets per second
for the mitigation request since the attack
mitigation is triggered.";
}
}
}
grouping signal-config {
description
"DOTS signal channel session configuration.";
leaf session-id {
type int32;
mandatory true;
description
"An identifier for the DOTS signal channel
session configuration data.";
}
leaf heartbeat-interval {
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type int16;
units "seconds";
default 30;
description
"DOTS agents regularly send heartbeats to each other
after mutual authentication is successfully
completed, in order to keep the DOTS signal channel
open.
'0' means that heartbeat mechanism is deactivated.";
reference
"RFC XXXX: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel";
}
leaf missing-hb-allowed {
type int16;
default 5;
description
"Maximum number of missing heartbeats allowed.";
reference
"RFC XXXX: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel";
}
leaf max-retransmit {
type int16;
default 3;
description
"Maximum number of retransmissions of a
Confirmable message.";
reference
"RFC XXXX: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel";
}
leaf ack-timeout {
type int16;
units "seconds";
default 2;
description
"Initial retransmission timeout value.";
reference
"Section 4.8 of RFC 7552.";
}
leaf ack-random-factor {
type decimal64 {
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fraction-digits 2;
}
default 1.5;
description
"Random factor used to influence the timing of
retransmissions.";
reference
"Section 4.8 of RFC 7552.";
}
leaf trigger-mitigation {
type boolean;
default true;
description
"If false, then mitigation is triggered
only when the DOTS server channel session is lost";
reference
"RFC XXXX: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel";
}
leaf config-interval {
type int32;
units "minutes";
description
"This parameter is returned by a DOTS server to
a requesting DOTS client to indicate the time interval
after which the DOTS client must contact the DOTS
server in order to retrieve the signal channel
configuration data.
This mechanism allows the update of the configuration
data if a change occurs.
For example, the new configuration may instruct
a DOTS client to cease heartbeats or reduce
heartbeat frequency.
'0' is used to disable this refresh mechanism.";
}
}
container dots-signal {
description
"Main container for DOTS signal message.
A DOTS signal message can be a mitigation message or
a configuration message.";
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choice message-type {
description
"Either a mitigation or a configuration message.";
case mitigation-scope {
description
"Mitigation scope of a mitigation message.";
uses mitigation-scope;
}
case configuration {
description
"Configuration message.";
uses signal-config;
}
}
}
}
<CODE ENDS>
6. Mapping Parameters to CBOR
All parameters in the payload of the DOTS signal channel MUST be
mapped to CBOR types as shown in Table 4 and are assigned an integer
key to save space. The recipient of the payload MAY reject the
information if it is not suitably mapped.
/----------------------+----------------+--------------------------\
| Parameter name | CBOR key | CBOR major type of value |
+----------------------+----------------+--------------------------+
| mitigation-scope | 1 | 5 (map) |
| scope | 2 | 5 (map) |
| mitigation-id | 3 | 0 (unsigned) |
| acl-list | 4 | 4 |
| target-port-range | 5 | 4 |
| lower-port | 6 | 0 |
| upper-port | 7 | 0 |
| target-protocol | 8 | 4 |
| target-fqdn | 9 | 4 |
| target-uri | 10 | 4 |
| alias-name | 11 | 4 |
| lifetime | 12 | 0 |
| attack-status | 13 | 0 |
| signal-config | 14 | 5 |
| heartbeat-interval | 15 | 0 |
| max-retransmit | 16 | 0 |
| ack-timeout | 17 | 0 |
| ack-random-factor | 18 | 7 |
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| min-value | 19 | 0 |
| max-value | 20 | 0 |
| status | 21 | 0 |
| conflict-information | 22 | 5 (map) |
| conflict-status | 23 | 0 |
| conflict-cause | 24 | 0 |
| retry-timer | 25 | 0 |
| bytes-dropped | 26 | 0 |
| bps-dropped | 27 | 0 |
| pkts-dropped | 28 | 0 |
| pps-dropped | 29 | 0 |
| session-id | 30 | 0 |
| trigger-mitigation | 31 | 7 (simple types) |
| missing-hb-allowed | 32 | 0 |
| current-value | 33 | 0 |
| mitigation-start | 34 | 7 (floating-point) |
| target-prefix | 35 | 4 (array) |
| client-identifier | 36 | 2 (byte string) |
| alt-server | 37 | 2 |
| alt-server-record | 38 | 4 |
| addr | 39 | 2 |
| ttl | 40 | 0 |
| conflict-scope | 41 | 5 (map) |
| acl-name | 42 | 2 |
| acl-type | 43 | 3 |
| config-interval | 44 | 0 |
\----------------------+----------------+--------------------------/
Table 4: CBOR mappings used in DOTS signal channel message
7. (D)TLS Protocol Profile and Performance Considerations
7.1. (D)TLS Protocol Profile
This section defines the (D)TLS protocol profile of DOTS signal
channel over (D)TLS and DOTS data channel over TLS.
There are known attacks on (D)TLS, such as man-in-the-middle and
protocol downgrade attacks. These are general attacks on (D)TLS and,
as such, they are not specific to DOTS over (D)TLS; please refer to
the (D)TLS RFCs for discussion of these security issues. DOTS agents
MUST adhere to the (D)TLS implementation recommendations and security
considerations of [RFC7525] except with respect to (D)TLS version.
Since DOTS encryption that relies upon (D)TLS is virtually a green-
field deployment, DOTS agents MUST implement only (D)TLS 1.2 or
later.
When a DOTS client is configured with a domain name of the DOTS
server, and connects to its configured DOTS server, the server may
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present it with a PKIX certificate. In order to ensure proper
authentication, a DOTS client MUST verify the entire certification
path per [RFC5280]. The DOTS client additionally uses [RFC6125]
validation techniques to compare the domain name with the certificate
provided.
A key challenge to deploying DOTS is the provisioning of DOTS
clients, including the distribution of keying material to DOTS
clients to enable the required mutual authentication of DOTS agents.
EST defines a method of certificate enrollment by which domains
operating DOTS servers may provide DOTS clients with all the
necessary cryptographic keying material, including a private key and
a certificate to authenticate themselves. One deployment option is
DOTS clients behave as EST clients for certificate enrollment from an
EST server provisioned by the mitigation provider. This document
does not specify which EST mechanism the DOTS client uses to achieve
initial enrollment.
Implementations compliant with this profile MUST implement all of the
following items:
o DTLS record replay detection (Section 3.3 of [RFC6347]) to protect
against replay attacks.
o (D)TLS session resumption without server-side state [RFC5077] to
resume session and convey the DOTS signal.
o Raw public keys [RFC7250] or PSK handshake [RFC4279] which reduces
the size of the ServerHello, and can be used by DOTS agents that
cannot obtain certificates.
Implementations compliant with this profile SHOULD implement all of
the following items to reduce the delay required to deliver a DOTS
signal:
o TLS False Start [RFC7918] which reduces round-trips by allowing
the TLS second flight of messages (ChangeCipherSpec) to also
contain the DOTS signal.
o Cached Information Extension [RFC7924] which avoids transmitting
the server's certificate and certificate chain if the client has
cached that information from a previous TLS handshake.
o TCP Fast Open [RFC7413] can reduce the number of round-trips to
convey DOTS signal.
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7.2. (D)TLS 1.3 Considerations
TLS 1.3 [I-D.ietf-tls-tls13] provides critical latency improvements
for connection establishment over TLS 1.2. The DTLS 1.3 protocol
[I-D.ietf-tls-dtls13] is based upon the TLS 1.3 protocol and provides
equivalent security guarantees. (D)TLS 1.3 provides two basic
handshake modes the DOTS signal channel can take advantage of:
o A full handshake mode in which a DOTS client can send a DOTS
mitigation request message after one round trip. This assumes no
packet loss is expereienced,
o 0-RTT mode in which the DOTS client can authenticate itself and
send DOTS mitigation request messages in the first message, thus
reducing handshake latency. 0-RTT only works if the DOTS client
has previously communicated with that DOTS server, which is very
likely with the DOTS signal channel.
The DOTS client has to establish a (D)TLS session with the DOTS
server during peacetime and share a PSK.
During a DDoS attack, the DOTS client can use the (D)TLS session
to convey the DOTS mitigation request message and, if there is no
response from the server after multiple retries, the DOTS client
can resume the (D)TLS session in 0-RTT mode using PSK.
Section 8 of [I-D.ietf-tls-tls13] discusses some mechanisms to
implement to limit the impact of replay attacks on 0-RTT data. If
TLS1.3 is used, DOTS servers must implement one of these
mechanisms.
A simplified TLS 1.3 handshake with 0-RTT DOTS mitigation request
message exchange is shown in Figure 23.
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DOTS Client DOTS Server
ClientHello
(Finished)
(0-RTT DOTS signal message)
(end_of_early_data) -------->
ServerHello
{EncryptedExtensions}
{ServerConfiguration}
{Certificate}
{CertificateVerify}
{Finished}
<-------- [DOTS signal message]
{Finished} -------->
[DOTS signal message] <-------> [DOTS signal message]
Figure 23: TLS 1.3 handshake with 0-RTT
7.3. MTU and Fragmentation
To avoid DOTS signal message fragmentation and the subsequent
decreased probability of message delivery, DOTS agents MUST ensure
that the DTLS record MUST fit within a single datagram. If the path
MTU is not known to the DOTS server, an IP MTU of 1280 bytes SHOULD
be assumed. The length of the URL MUST NOT exceed 256 bytes. If UDP
is used to convey the DOTS signal messages then the DOTS client must
consider the amount of record expansion expected by the DTLS
processing when calculating the size of CoAP message that fits within
the path MTU. Path MTU MUST be greater than or equal to [CoAP
message size + DTLS overhead of 13 octets + authentication overhead
of the negotiated DTLS cipher suite + block padding (Section 4.1.1.1
of [RFC6347]). If the request size exceeds the path MTU then the
DOTS client MUST split the DOTS signal into separate messages, for
example the list of addresses in the 'target-prefix' parameter could
be split into multiple lists and each list conveyed in a new PUT
request.
Implementation Note: DOTS choice of message size parameters works
well with IPv6 and with most of today's IPv4 paths. However, with
IPv4, it is harder to reliably ensure that there is no IP
fragmentation. If IPv4 path MTU is unknown, implementations may want
to limit themselves to more conservative IPv4 datagram sizes such as
576 bytes, as per [RFC0791]. IP packets whose size does not exceed
576 bytes should never need to be fragmented: therefore, sending a
maximum of 500 bytes of DOTS signal over a UDP datagram will
generally avoid IP fragmentation.
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8. Mutual Authentication of DOTS Agents & Authorization of DOTS Clients
(D)TLS based upon client certificate can be used for mutual
authentication between DOTS agents. If a DOTS gateway is involved,
DOTS clients and DOTS gateways MUST perform mutual authentication;
only authorized DOTS clients are allowed to send DOTS signals to a
DOTS gateway. The DOTS gateway and the DOTS server MUST perform
mutual authentication; a DOTS server only allows DOTS signals from an
authorized DOTS gateway, thereby creating a two-link chain of
transitive authentication between the DOTS client and the DOTS
server.
+-----------------------------------------------+
| example.com domain +---------+ |
| | AAA | |
| +---------------+ | Server | |
| | Application | +------+--+ |
| | server +<-----------------+ ^ |
| | (DOTS client) | | | |
| +---------------+ | | |
| V V | example.net domain
| +-----+----+--+ | +---------------+
| +--------------+ | | | | |
| | Guest +<-----x----->+ DOTS +<------>+ DOTS |
| | (DOTS client)| | Gateway | | | Server |
| +--------------+ | | | | |
| +----+--------+ | +---------------+
| ^ |
| | |
| +----------------+ | |
| | DDOS detector | | |
| | (DOTS client) +<---------------+ |
| +----------------+ |
+-----------------------------------------------+
Figure 24: Example of Authentication and Authorization of DOTS Agents
In the example depicted in Figure 24, the DOTS gateway and DOTS
clients within the 'example.com' domain mutually authenticate with
each other. After the DOTS gateway validates the identity of a DOTS
client, it communicates with the AAA server in the 'example.com'
domain to determine if the DOTS client is authorized to request DDoS
mitigation. If the DOTS client is not authorized, a 4.01
(Unauthorized) is returned in the response to the DOTS client. In
this example, the DOTS gateway only allows the application server and
DDoS attack detector to request DDOS mitigation, but does not permit
the user of type 'guest' to request DDoS mitigation.
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Also, DOTS gateways and servers located in different domains MUST
perform mutual authentication (e.g., using certificates). A DOTS
server will only allow a DOTS gateway with a certificate for a
particular domain to request mitigation for that domain. In
reference to Figure 24, the DOTS server only allows the DOTS gateway
to request mitigation for 'example.com' domain and not for other
domains.
9. IANA Considerations
This specification registers a service port (Section 9.1), an URI
suffix in the Well-Known URIs registry (Section 9.2), a CoAP response
code (Section 9.3), a YANG module (Section 9.5). It also creates a
registry for mappings to CBOR (Section 9.4).
9.1. DOTS Signal Channel UDP and TCP Port Number
IANA is requested to assign the port number TBD to the DOTS signal
channel protocol for both UDP and TCP from the "Service Name and
Transport Protocol Port Number Registry" available at
https://www.iana.org/assignments/service-names-port-numbers/service-
names-port-numbers.xhtml.
The assignment of port number 4646 is strongly suggested, as 4646 is
the ASCII decimal value for ".." (DOTS).
9.2. Well-Known 'dots' URI
This document requests IANA to register the 'dots' well-known URI in
the Well-Known URIs registry (https://www.iana.org/assignments/well-
known-uris/well-known-uris.xhtml) as defined by [RFC5785].
URI suffix: dots
Change controller: IETF
Specification document(s): This RFC
Related information: None
9.3. CoAP Response Code
IANA is requested to add the following entry to the "CoAP Response
Codes" sub-registry available at https://www.iana.org/assignments/
core-parameters/core-parameters.xhtml#response-codes:
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+------+------------------+-----------+
| Code | Description | Reference |
+------+------------------+-----------+
| 3.00 | Alternate server | [RFCXXXX] |
+------+------------------+-----------+
Table 4: CoAP Response Code
9.4. DOTS Signal Channel CBOR Mappings Registry
The document requests IANA to create a new registry, entitled "DOTS
Signal Channel CBOR Mappings Registry". The structure of this
registry is provided in Section 9.4.1.
The registry is initially populated with the values in Section 9.4.2.
Values from that registry MUST be assigned via Expert Review
[RFC8126].
9.4.1. Registration Template
Parameter name:
Parameter name as used in the DOTS signal channel.
CBOR Key Value:
Key value for the parameter. The key value MUST be an integer in
the 1-65536 range. The key values in the 32758-65536 range are
assigned to Vendor-Specific parameters.
CBOR Major Type:
CBOR Major type and optional tag for the claim.
Change Controller:
For Standards Track RFCs, list the "IESG". For others, give the
name of the responsible party. Other details (e.g., postal
address, email address, home page URI) may also be included.
Specification Document(s):
Reference to the document or documents that specify the parameter,
preferably including URIs that can be used to retrieve copies of
the documents. An indication of the relevant sections may also be
included but is not required.
9.4.2. Initial Registry Contents
o Parameter Name: mitigation-scope
o CBOR Key Value: 1
o CBOR Major Type: 5
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o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: scope
o CBOR Key Value: 2
o CBOR Major Type: 5
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: mitigation-id
o CBOR Key Value: 3
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: acl-type
o CBOR Key Value: 4
o CBOR Major Type: 4
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: target-port-range
o CBOR Key Value: 5
o CBOR Major Type: 4
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: lower-port
o CBOR Key Value: 6
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: upper-port
o CBOR Key Value: 7
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: target-protocol
o CBOR Key Value: 8
o CBOR Major Type: 4
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: target-fqdn
o CBOR Key Value: 9
o CBOR Major Type: 4
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o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: target-uri
o CBOR Key Value: 10
o CBOR Major Type: 4
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: alias-name
o CBOR Key Value: 11
o CBOR Major Type: 4
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: lifetime
o CBOR Key Value: 12
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: attack-status
o CBOR Key Value: 13
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: signal-config
o CBOR Key Value: 14
o CBOR Major Type: 5
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: heartbeat-interval
o CBOR Key Value: 15
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: max-retransmit
o CBOR Key Value: 16
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: ack-timeout
o CBOR Key Value: 17
o CBOR Major Type: 0
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o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: ack-random-factor
o CBOR Key Value: 18
o CBOR Major Type: 7
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: min-value
o CBOR Key Value: 19
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: max-value
o CBOR Key Value: 20
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: status
o CBOR Key Value: 21
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: conflict-information
o CBOR Key Value: 22
o CBOR Major Type: 5
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: conflict-status
o CBOR Key Value: 23
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: conflict-cause
o CBOR Key Value: 24
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: retry-timer
o CBOR Key Value: 25
o CBOR Major Type: 0
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o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: bytes-dropped
o CBOR Key Value: 26
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: bps-dropped
o CBOR Key Value: 27
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: pkts-dropped
o CBOR Key Value: 28
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: pps-dropped
o CBOR Key Value: 29
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: session-id
o CBOR Key Value: 30
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: trigger-mitigation
o CBOR Key Value: 31
o CBOR Major Type: 7
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: missing-hb-allowed
o CBOR Key Value: 32
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: current-value
o CBOR Key Value: 33
o CBOR Major Type: 0
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o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: mitigation-start
o CBOR Key Value: 34
o CBOR Major Type: 7
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: target-prefix
o CBOR Key Value: 35
o CBOR Major Type: 4
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: client-identifier
o CBOR Key Value: 36
o CBOR Major Type: 2
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: alt-server
o CBOR Key Value: 37
o CBOR Major Type: 2
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: alt-server-record
o CBOR Key Value: 38
o CBOR Major Type: 4
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: addr
o CBOR Key Value: 39
o CBOR Major Type: 2
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: ttl
o CBOR Key Value: 40
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: conflict-scope
o CBOR Key Value: 41
o CBOR Major Type: 5
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o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: acl-name
o CBOR Key Value: 42
o CBOR Major Type: 2
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: acl-type
o CBOR Key Value: 43
o CBOR Major Type: 3
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: config-interval
o CBOR Key Value: 44
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
9.5. DOTS Signal Channel YANG Module
This document requests IANA to register the following URI in the
"IETF XML Registry" [RFC3688]:
URI: urn:ietf:params:xml:ns:yang:ietf-dots-signal
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
This document requests IANA to register the following YANG module in
the "YANG Module Names" registry [RFC7950].
name: ietf-signal
namespace: urn:ietf:params:xml:ns:yang:ietf-dots-signal
prefix: signal
reference: RFC XXXX
10. Implementation Status
[Note to RFC Editor: Please remove this section and reference to
[RFC7942] prior to publication.]
This section records the status of known implementations of the
protocol defined by this specification at the time of posting this
Internet-Draft, and is based upon a proposal described in [RFC7942].
The description of implementations in this section is intended to
assist the IETF in its decision-making process when progressing
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drafts to RFCs. Please note that the listing of any individual
implementation here does not imply endorsement by the IETF.
Furthermore, no effort has been spent to verify the information
presented here, and which was provided by individuals. This is not
intended as, and must not be construed to be, a catalog of available
implementations or features. Readers are advised to note that other
implementations may exist.
According to [RFC7942], "this will allow reviewers and working groups
to assign due consideration to documents that have the benefit of
running code, which may serve as evidence of valuable experimentation
and feedback that have made the implemented protocols more mature.
It is up to the individual working groups to use this information as
they see fit".
10.1. nttdots
Organization: NTT Communication is developing a DOTS client and
DOTS server software based on DOTS signal channel specified in
this draft. It will be open-sourced.
Description: Early implementation of DOTS protocol. It is aimed to
implement a full DOTS protocol specification in accordance with
the nurturing DOTS protocol.
Implementation: https://github.com/nttdots/go-dots
Level of maturity: It is an early implementation of the DOTS
protocol. Messaging between DOTS clients and DOTS servers has
been tested. Level of maturity will increase in accordance with
the nurturing DOTS protocol.
Coverage: Capability of DOTS client: sending DOTS messages to the
DOTS server in CoAP over DTLS as dots-signal. Capability of DOTS
server: receiving dots-signal, validating received dots-signal,
starting mitigation by handing over the dots-signal to DDOS
mitigator.
Licensing: It will be open-sourced with BSD 3-clause license.
Implementation experience: It is implemented in Go-lang. Core
specification of signaling is mature to be implemented, however,
finding good libraries(like DTLS, CoAP) is rather difficult.
Contact: Kaname Nishizuka <kaname@nttv6.jp>
11. Security Considerations
Authenticated encryption MUST be used for data confidentiality and
message integrity. The interaction between the DOTS agents requires
Datagram Transport Layer Security (DTLS) and Transport Layer Security
(TLS) with a cipher suite offering confidentiality protection and the
guidance given in [RFC7525] MUST be followed to avoid attacks on
(D)TLS. The (D)TLS protocol profile for DOTS signal channel is
specified in Section 7.
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A single DOTS signal channel between DOTS agents can be used to
exchange multiple DOTS signal messages. To reduce DOTS client and
DOTS server workload, DOTS clients SHOULD re-use the (D)TLS session.
If TCP is used between DOTS agents, an attacker may be able to inject
RST packets, bogus application segments, etc., regardless of whether
TLS authentication is used. Because the application data is TLS
protected, this will not result in the application receiving bogus
data, but it will constitute a DoS on the connection. This attack
can be countered by using TCP-AO [RFC5925]. If TCP-AO is used, then
any bogus packets injected by an attacker will be rejected by the
TCP-AO integrity check and therefore will never reach the TLS layer.
In order to prevent leaking internal information outside a client-
domain, DOTS gateways located in the client-domain SHOULD NOT reveal
the identification information that pertains to internal DOTS clients
(client-identifier) unless explicitly configured to do so.
Special care should be taken in order to ensure that the activation
of the proposed mechanism will not impact the stability of the
network (including connectivity and services delivered over that
network).
Involved functional elements involved in the DDoS cooperation system
must exchange instructions and notification over a secure and
authenticated channel. Adequate filters can apply to avoid that
nodes outside a trusted domain can inject illegitimate requests.
Attacks can be initiated from within the trusted domain if an entity
has been corrupted. Adequate means to monitor trusted nodes should
also be enabled.
12. Contributors
The following individuals have contributed to this document:
Mike Geller Cisco Systems, Inc. 3250 Florida 33309 USA Email:
mgeller@cisco.com
Robert Moskowitz HTT Consulting Oak Park, MI 42837 United States
Email: rgm@htt-consult.com
Dan Wing Email: dwing-ietf@fuggles.com
13. Acknowledgements
Thanks to Christian Jacquenet, Roland Dobbins, Roman D. Danyliw,
Michael Richardson, Ehud Doron, Kaname Nishizuka, Dave Dolson, Liang
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Xia, Gilbert Clark, and Nesredien Suleiman for the discussion and
comments.
Special thanks to Jon Shallow for the careful reviews and inputs that
enhanced this specification.
14. References
14.1. Normative References
[I-D.ietf-core-coap-tcp-tls]
Bormann, C., Lemay, S., Tschofenig, H., Hartke, K.,
Silverajan, B., and B. Raymor, "CoAP (Constrained
Application Protocol) over TCP, TLS, and WebSockets",
draft-ietf-core-coap-tcp-tls-10 (work in progress),
October 2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC4279] Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key
Ciphersuites for Transport Layer Security (TLS)",
RFC 4279, DOI 10.17487/RFC4279, December 2005,
<https://www.rfc-editor.org/info/rfc4279>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
[RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
Uniform Resource Identifiers (URIs)", RFC 5785,
DOI 10.17487/RFC5785, April 2010,
<https://www.rfc-editor.org/info/rfc5785>.
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[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
June 2010, <https://www.rfc-editor.org/info/rfc5925>.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
2011, <https://www.rfc-editor.org/info/rfc6125>.
[RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234,
DOI 10.17487/RFC6234, May 2011,
<https://www.rfc-editor.org/info/rfc6234>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J.,
Weiler, S., and T. Kivinen, "Using Raw Public Keys in
Transport Layer Security (TLS) and Datagram Transport
Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250,
June 2014, <https://www.rfc-editor.org/info/rfc7250>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/info/rfc7252>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <https://www.rfc-editor.org/info/rfc7525>.
[RFC7641] Hartke, K., "Observing Resources in the Constrained
Application Protocol (CoAP)", RFC 7641,
DOI 10.17487/RFC7641, September 2015,
<https://www.rfc-editor.org/info/rfc7641>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
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[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8132] van der Stok, P., Bormann, C., and A. Sehgal, "PATCH and
FETCH Methods for the Constrained Application Protocol
(CoAP)", RFC 8132, DOI 10.17487/RFC8132, April 2017,
<https://www.rfc-editor.org/info/rfc8132>.
14.2. Informative References
[I-D.ietf-core-comi]
Veillette, M., Stok, P., Pelov, A., and A. Bierman, "CoAP
Management Interface", draft-ietf-core-comi-02 (work in
progress), December 2017.
[I-D.ietf-core-yang-cbor]
Veillette, M., Pelov, A., Somaraju, A., Turner, R., and A.
Minaburo, "CBOR Encoding of Data Modeled with YANG",
draft-ietf-core-yang-cbor-05 (work in progress), August
2017.
[I-D.ietf-dots-architecture]
Mortensen, A., Andreasen, F., Reddy, T.,
christopher_gray3@cable.comcast.com, c., Compton, R., and
N. Teague, "Distributed-Denial-of-Service Open Threat
Signaling (DOTS) Architecture", draft-ietf-dots-
architecture-05 (work in progress), October 2017.
[I-D.ietf-dots-data-channel]
Reddy, T., Boucadair, M., Nishizuka, K., Xia, L., Patil,
P., Mortensen, A., and N. Teague, "Distributed Denial-of-
Service Open Threat Signaling (DOTS) Data Channel", draft-
ietf-dots-data-channel-10 (work in progress), December
2017.
[I-D.ietf-dots-requirements]
Mortensen, A., Moskowitz, R., and T. Reddy, "Distributed
Denial of Service (DDoS) Open Threat Signaling
Requirements", draft-ietf-dots-requirements-08 (work in
progress), December 2017.
[I-D.ietf-dots-use-cases]
Dobbins, R., Migault, D., Fouant, S., Moskowitz, R.,
Teague, N., Xia, L., and K. Nishizuka, "Use cases for DDoS
Open Threat Signaling", draft-ietf-dots-use-cases-09 (work
in progress), November 2017.
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[I-D.ietf-netmod-yang-tree-diagrams]
Bjorklund, M. and L. Berger, "YANG Tree Diagrams", draft-
ietf-netmod-yang-tree-diagrams-02 (work in progress),
October 2017.
[I-D.ietf-tls-dtls13]
Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version
1.3", draft-ietf-tls-dtls13-22 (work in progress),
November 2017.
[I-D.ietf-tls-tls13]
Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", draft-ietf-tls-tls13-22 (work in progress),
November 2017.
[proto_numbers]
"IANA, "Protocol Numbers"", 2011,
<http://www.iana.org/assignments/protocol-numbers>.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC4340] Kohler, E., Handley, M., and S. Floyd, "Datagram
Congestion Control Protocol (DCCP)", RFC 4340,
DOI 10.17487/RFC4340, March 2006,
<https://www.rfc-editor.org/info/rfc4340>.
[RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing
(CIDR): The Internet Address Assignment and Aggregation
Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August
2006, <https://www.rfc-editor.org/info/rfc4632>.
[RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
Denial-of-Service Considerations", RFC 4732,
DOI 10.17487/RFC4732, December 2006,
<https://www.rfc-editor.org/info/rfc4732>.
[RFC4787] Audet, F., Ed. and C. Jennings, "Network Address
Translation (NAT) Behavioral Requirements for Unicast
UDP", BCP 127, RFC 4787, DOI 10.17487/RFC4787, January
2007, <https://www.rfc-editor.org/info/rfc4787>.
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[RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol",
RFC 4960, DOI 10.17487/RFC4960, September 2007,
<https://www.rfc-editor.org/info/rfc4960>.
[RFC4987] Eddy, W., "TCP SYN Flooding Attacks and Common
Mitigations", RFC 4987, DOI 10.17487/RFC4987, August 2007,
<https://www.rfc-editor.org/info/rfc4987>.
[RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
"Transport Layer Security (TLS) Session Resumption without
Server-Side State", RFC 5077, DOI 10.17487/RFC5077,
January 2008, <https://www.rfc-editor.org/info/rfc5077>.
[RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
"Session Traversal Utilities for NAT (STUN)", RFC 5389,
DOI 10.17487/RFC5389, October 2008,
<https://www.rfc-editor.org/info/rfc5389>.
[RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with
Dual-Stack Hosts", RFC 6555, DOI 10.17487/RFC6555, April
2012, <https://www.rfc-editor.org/info/rfc6555>.
[RFC6724] Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown,
"Default Address Selection for Internet Protocol Version 6
(IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012,
<https://www.rfc-editor.org/info/rfc6724>.
[RFC6887] Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
DOI 10.17487/RFC6887, April 2013,
<https://www.rfc-editor.org/info/rfc6887>.
[RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
"Enrollment over Secure Transport", RFC 7030,
DOI 10.17487/RFC7030, October 2013,
<https://www.rfc-editor.org/info/rfc7030>.
[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
October 2013, <https://www.rfc-editor.org/info/rfc7049>.
[RFC7413] Cheng, Y., Chu, J., Radhakrishnan, S., and A. Jain, "TCP
Fast Open", RFC 7413, DOI 10.17487/RFC7413, December 2014,
<https://www.rfc-editor.org/info/rfc7413>.
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[RFC7452] Tschofenig, H., Arkko, J., Thaler, D., and D. McPherson,
"Architectural Considerations in Smart Object Networking",
RFC 7452, DOI 10.17487/RFC7452, March 2015,
<https://www.rfc-editor.org/info/rfc7452>.
[RFC7589] Badra, M., Luchuk, A., and J. Schoenwaelder, "Using the
NETCONF Protocol over Transport Layer Security (TLS) with
Mutual X.509 Authentication", RFC 7589,
DOI 10.17487/RFC7589, June 2015,
<https://www.rfc-editor.org/info/rfc7589>.
[RFC7918] Langley, A., Modadugu, N., and B. Moeller, "Transport
Layer Security (TLS) False Start", RFC 7918,
DOI 10.17487/RFC7918, August 2016,
<https://www.rfc-editor.org/info/rfc7918>.
[RFC7924] Santesson, S. and H. Tschofenig, "Transport Layer Security
(TLS) Cached Information Extension", RFC 7924,
DOI 10.17487/RFC7924, July 2016,
<https://www.rfc-editor.org/info/rfc7924>.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>.
[RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
RFC 7951, DOI 10.17487/RFC7951, August 2016,
<https://www.rfc-editor.org/info/rfc7951>.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <https://www.rfc-editor.org/info/rfc8085>.
Authors' Addresses
Tirumaleswar Reddy
McAfee, Inc.
Embassy Golf Link Business Park
Bangalore, Karnataka 560071
India
Email: kondtir@gmail.com
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Mohamed Boucadair
Orange
Rennes 35000
France
Email: mohamed.boucadair@orange.com
Prashanth Patil
Cisco Systems, Inc.
Email: praspati@cisco.com
Andrew Mortensen
Arbor Networks, Inc.
2727 S. State St
Ann Arbor, MI 48104
United States
Email: amortensen@arbor.net
Nik Teague
Verisign, Inc.
United States
Email: nteague@verisign.com
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