QUIC-LB: Generating Routable QUIC Connection IDs
draft-duke-quic-load-balancers-02
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| Author | Martin Duke | ||
| Last updated | 2018-09-17 | ||
| Replaced by | draft-ietf-quic-load-balancers | ||
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draft-duke-quic-load-balancers-02
QUIC M. Duke
Internet-Draft F5 Networks, Inc.
Intended status: Standards Track September 17, 2018
Expires: March 21, 2019
QUIC-LB: Generating Routable QUIC Connection IDs
draft-duke-quic-load-balancers-02
Abstract
QUIC connection IDs allow continuation of connections across address/
port 4-tuple changes, and can store routing information for stateless
or low-state load balancers. They also can prevent linkability of
connections across deliberate address migration through the use of
protected communications between client and server. This creates
issues for load-balancing intermediaries. This specification
standardizes methods for encoding routing information and proposes an
optional protocol called QUIC_LB to exchange the parameters of that
encoding.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 21, 2019.
Copyright Notice
Copyright (c) 2018 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
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Protocol Objectives . . . . . . . . . . . . . . . . . . . . . 4
2.1. Simplicity . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Security . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3. Robustness to Middleboxes . . . . . . . . . . . . . . . . 5
2.4. Load Balancer Chains . . . . . . . . . . . . . . . . . . 5
3. Routing Algorithms . . . . . . . . . . . . . . . . . . . . . 5
3.1. Plaintext CID Algorithm . . . . . . . . . . . . . . . . . 6
3.1.1. Load Balancer Actions . . . . . . . . . . . . . . . . 6
3.1.2. Server Actions . . . . . . . . . . . . . . . . . . . 6
3.2. Encrypted CID Algorithm . . . . . . . . . . . . . . . . . 7
3.2.1. Load Balancer Actions . . . . . . . . . . . . . . . . 7
3.2.2. Server Actions . . . . . . . . . . . . . . . . . . . 8
4. Protocol Description . . . . . . . . . . . . . . . . . . . . 8
4.1. Out of band sharing . . . . . . . . . . . . . . . . . . . 8
4.2. QUIC-LB Message Exchange . . . . . . . . . . . . . . . . 8
4.2.1. Packet Header Format . . . . . . . . . . . . . . . . 9
4.2.2. Ack Payload . . . . . . . . . . . . . . . . . . . . . 9
4.2.3. Fail Payload . . . . . . . . . . . . . . . . . . . . 10
4.2.4. Routing Info Payload . . . . . . . . . . . . . . . . 11
4.2.5. Encrypted CID Payload . . . . . . . . . . . . . . . . 11
4.2.6. Server ID Payload . . . . . . . . . . . . . . . . . . 12
4.2.7. Modulus Payload . . . . . . . . . . . . . . . . . . . 13
5. Configuration Requirements . . . . . . . . . . . . . . . . . 13
6. Security Considerations . . . . . . . . . . . . . . . . . . . 14
6.1. Outside attackers . . . . . . . . . . . . . . . . . . . . 14
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
8.1. Normative References . . . . . . . . . . . . . . . . . . 15
8.2. Informative References . . . . . . . . . . . . . . . . . 15
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 15
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 15
B.1. Since draft-duke-quic-load-balancers-00 . . . . . . . . . 15
B.2. Since draft-duke-quic-load-balancers-01 . . . . . . . . . 15
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16
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1. Introduction
QUIC packets usually contain a connection ID to allow endpoints to
associate packets with different address/port 4-tuples to the same
connection context. This feature makes connections robust in the
event of NAT rebinding. QUIC endpoints designate the connection ID
which peers use to address packets. Server-generated connection IDs
create a potential need for out-of-band communication to support
QUIC.
QUIC allows servers (or load balancers) to designate an initial
connection ID to encode useful routing information for load
balancers. It also encourages servers, in packets protected by
cryptography, to provide additional connection IDs to the client.
This allows clients that know they are going to change IP address or
port to use a separate connection ID on the new path, thus reducing
linkability as clients move through the world.
There is a tension between the requirements to provide routing
information and mitigate linkability. Ultimately, because new
connection IDs are in protected packets, they must be generated at
the server if the load balancer does not have access to the
connection keys. However, it is the load balancer that has the
context necessary to generate a connection ID that encodes useful
routing information. In the absence of any shared state between load
balancer and server, the load balancer must maintain a relatively
expensive table of server-generated connection IDs, and will not
route packets correctly if they use a connection ID that was
originally communicated in a protected NEW_CONNECTION_ID frame.
This specification provides a method of coordination between QUIC
servers and low-state load balancers to support connection IDs that
encode routing information. It describes desirable properties of a
solution, and then specifies a protocol that provides those
properties. This protocol supports multiple encoding schemes that
increase in complexity as they address paths between load balancer
and server with weaker trust dynamics.
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
In this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to be
interpreted as carrying significance described in RFC 2119.
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In this document, "client" and "server" refer to the endpoints of a
QUIC connection unless otherwise indicated. A "load balancer" is an
intermediary for that connection that does not possess QUIC
connection keys, but it may rewrite IP addresses or conduct other IP
or UDP processing.
Note that stateful load balancers that act as proxies, by terminating
a QUIC connection with the client and then retrieving data from the
server using QUIC or another protocol, are treated as a server with
respect to this specification.
When discussing security threats to QUIC-LB, we distinguish between
"inside observers" and "outside observers." The former lie on the
path between the load balancer and server, which often but not always
lies inside the server's data center or cloud deployment. Outside
observers are on the path between the load balancer and client.
"Off-path" attackers, though not on any data path, may also be
"inside" or "outside" depending on whether not they have network
access to the server without intermediation by the load balancer and/
or other security devices.
2. Protocol Objectives
2.1. Simplicity
QUIC is intended to provide unlinkability across connection
migration, but servers are not required to provide additional
connection IDs that effectively prevent linkability. If the
coordination scheme is too difficult to implement, servers behind
load balancers using connection IDs for routing will use trivially
linkable connection IDs. Clients will therefore be forced choose
between terminating the connection during migration or remaining
linkable, subverting a design objective of QUIC.
The solution should be both simple to implement and require little
additional infrastructure for cryptographic keys, etc.
2.2. Security
In the limit where there are very few connections to a pool of
servers, no scheme can prevent the linking of two connection IDs with
high probability. In the opposite limit, where all servers have many
connections that start and end frequently, it will be difficult to
associate two connection IDs even if they are known to map to the
same server.
QUIC-LB is relevant in the region between these extremes: when the
information that two connection IDs map to the same server is helpful
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to linking two connection IDs. Obviously, any scheme that
transparently communicates this mapping to outside observers
compromises QUIC's defenses against linkability.
However, concealing this mapping from inside observers is beyond the
scope of QUIC-LB. By simply observing Link-Layer and/or Network-
Layer addresses of packets containing distinct connection IDs, it is
trivial to determine that they map to the same server, even if
connection IDs are entirely random and do not encode routing
information. Schemes that conceal these addresses (e.g., IPsec) can
also conceal QUIC-LB messages.
Inside observers are generally able to mount Denial of Service (DoS)
attacks on QUIC connections regardless of Connection ID schemes.
However, QUIC-LB should protect against Denial of Service due to
inside off-path attackers in cases where such attackers are possible.
2.3. Robustness to Middleboxes
The path between load balancer and server may pass through
middleboxes that could drop the coordination messages in this
protocol. It is therefore advantageous to make messages resemble
QUIC traffic as much as possible, as any viable path must obviously
admit QUIC traffic.
2.4. Load Balancer Chains
While it is possible to construct a scheme that supports multiple
low-state load balancers in the path, by using different parts of the
connection ID to encoding routing information for each load balancer,
this use case is out of scope for QUIC-LB.
3. Routing Algorithms
In QUIC-LB, load balancers do not send individual connection IDs to
servers. Instead, they communicate the parameters of an algorithm to
generate routable connection IDs.
The algorithms differ in the complexity of configuration at both load
balancer and server. Increasing complexity improves obfuscation of
the server mapping.
The load balancer SHOULD route Initial and 0-RTT packets from the
client using an alternate algorithm. Note that the SCID in these
packets may not be long enough to represent all the routing bits.
This algorithm SHOULD generate consistent results for Initial and
0RTT packets that arrive with the same source and destination
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connection ID. The load balancer algorithms below apply to all
incoming Handshake and 1-RTT packets.
3.1. Plaintext CID Algorithm
3.1.1. Load Balancer Actions
The load balancer selects an arbitrary set of bits of the server
connection ID (SCID) that it will use to route to a given server,
called the "routing bits". The number of bits MUST have enough
entropy to have a different code point for each server, and SHOULD
have enough entropy so that there are many codepoints for each
server.
The load balancer selects a divisor that MUST be larger than the
number of servers. It SHOULD be large enough to accommodate
reasonable increases in the number of servers.
The load balancer also assigns each server a "modulus", an integer
between 0 and the divisor minus 1. These MUST be unique for each
server.
The load balancer shares these three values with servers, as
explained in Section 4.
Upon receipt of a QUIC packet that is not of type Initial or 0-RTT,
the load balancer extracts the selected bits of the SCID and
expresses them as an unsigned integer of that length. The load
balancer then divides the result by the chosen divisor. The modulus
of this operation maps to the modulus for the destination server. .
Note that any SCID that contains a server's modulus, plus an
arbitrary integer multiple of the divisor, in the routing bits is
routable to that server regardless of the contents of the non-routing
bits. Outside observers that do not know the divisor or the routing
bits will therefore have difficulty identifying that two SCIDs route
to the same server.
Note also that not all Connection IDs are necessarily routable, as
the computed modulus may not match one assigned to any server. Load
balancers SHOULD drop these packets if not a QUIC Initial or 0-RTT
packet.
3.1.2. Server Actions
The server may choose any connection ID length that can represent all
of the routing bits.
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When a server needs a new connection ID, it adds an arbitrary
nonnegative integer multiple of the divisor to its modulus, without
exceeding the maximum integer value implied by the number of routing
bits. The choice of multiple should appear random within these
constraints.
The server encodes the result in the routing bits. It MAY put any
other value into the non-routing bits. The non-routing bits SHOULD
appear random to observers.
3.2. Encrypted CID Algorithm
The Encrypted CID algorithm provides true cryptographic protection,
rather than mere obfuscation, at the cost of additional per-packet
processing at the load balancer to decrypt every incoming connection
ID except for Initial and 0RTT packets.
3.2.1. Load Balancer Actions
The load balancer assigns a server ID to every server in its pool,
and determines a server ID length (in octets) sufficiently large to
encode all server IDs, including potential future servers. The
server ID will be encoded in the first octets of the connection ID.
The load balancer also selects a connection ID length that all
servers must use, and an 16-octet AES-CTR key to use for connection
ID decryption.
The load balancer shares these three values with servers, as
explained in Section 4.
Upon receipt of a QUIC packet that is not of type Initial or 0-RTT,
the load balancer extracts as many of the earliest octets from the
destination connection ID as necessary to match the server ID length.
The load balancer decrypts the server ID using 128-bit AES in counter
(CTR) mode, much like QUIC packet number decryption. The counter
input to AES-CTR is the bytes of the connection ID that do not
constitute the encrypted server ID.
server_id = AES-CTR(key, non-server-id-bytes, encrypted_server_id)
The output of the decryption is the server ID that the load balancer
uses for routing.
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3.2.2. Server Actions
When generating a routable connection ID, the server writes its
provided server ID into the server ID octets, and arbitrary bits into
the remaining required connection ID octets. These arbitrary bits
MAY encode additional information, but SHOULD appear essentially
random to observers.
The server then encrypts the server ID bytes using 128-bit AES in
counter (CTR) mode, much like QUIC packet number encryption. The
counter input to AES-CTR is the bytes of the connection ID that do
not constitute the encrypted server ID.
encrypted_server_id = AES-CTR(key, non_server_id_bytes, server-id)
4. Protocol Description
The fundamental protocol requirement is to share the choice of
routing algorithm, and the relevant parameters for that algorithm,
between load balancer and server.
For Plaintext CID Routing, this consists of the Routing Bits,
Divisor, and Modulus. The Modulus is unique to each server, but the
others MUST be global.
For Encrypted CID Routing, this consists of the Server ID, Server ID
Length, Key, and Connection ID Length. The Server ID is unique to
each server, but the others MUST be global.
4.1. Out of band sharing
When there are concerns about the integrity of the path between load
balancer and server, operators may share routing information using an
out-of-band technique, which is out of the scope of this
specification.
To simplify configuration, the global parameters can be shared out-
of-band, while the load balancer sends the unique server IDs via the
truncated message formats presented below.
4.2. QUIC-LB Message Exchange
QUIC-LB load balancers send the encoding parameters to servers as
they discover the servers, using a single packet to each that
resembles QUIC. They periodically retransmit this packet to each
server until that server responds with a QUIC-LB ack. Specifics of
this retransmission are implementation-dependent.
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These message formats are specific to QUICv2 and experimental
versions leading up to QUICv2. They may require revision for future
versions of QUIC.
4.2.1. Packet Header Format
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+
| Type = 0xfb |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x00 |
+-+-+-+-+-+-+-+-+
Figure 1: QUIC-LB Header
QUIC-LB messages are QUIC packets with a long header and zero length
connection IDs. They are sent when a load balancer boots up, or
detects a new server in the pool. QUIC-LB packets are delivered in a
UDP datagram.
The type field is 0xfb, which is otherwise unused in QUICv2.
The Version field allows QUIC-LB to use the Version Negotiation
mechanism. All messages in this specification are specific to
QUICv2, as future QUIC versions may use the 0xfb packet type for
other purposes. Therefore, the Version field should be set as the
codepoint for QUICv2 as defined in [QUIC-TRANSPORT].
Load balancers MUST cease sending QUIC-LB packets of this version to
a server when that server sends a Version Negotiation packet that
does not advertise the version.
The 0x00 byte indicates that there are no connection IDs present in
the header.
The remainder of the packet is the payload. This has multiple
formats.
4.2.2. Ack Payload
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0x00 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Token (64) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Ack Payload
The Ack Payload consists of nine octets. Servers send this payload
after receipt of any acceptable QUIC-LB packet from a load balancer.
The token field echoes the token field from the acknowledged packet.
Load balancers MUST retransmit a QUIC-LB packet if not followed by a
valid Ack Payload or Version Negotiation Packet from the destination
after a reasonable interval.
4.2.3. Fail Payload
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0x01 | Supp. Type | Supp. Type | ...
+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Token (64) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Fail Payload
Servers MUST send a Fail Payload upon receipt of a payload type which
they do not support, or if they do not possess all of the implied
out-of-band configuration to support a particular payload type.
After the type octet, servers append additional octets to list all
payload types they support.
The token field echoes the token field from the acknowledged packet.
Upon receipt of a Fail Payload, Load Balancers MUST either send a
QUIC-LB payload the server supports, or remove the server from the
server pool.
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4.2.4. Routing Info Payload
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0x02 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Token (64) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Routing Bit Mask (144) +
| |
+ +
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Modulus (16) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Divisor (16) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Routing Info Payload
The Type Octet indicates that this is a Routing Info Payload, which
contains all parameters for the plaintext CID algorithm.
The Token is an 8-octet field that both entities obtain at
configuration time. It is used to verify that the sender is not an
inside off-path attacker. Servers SHOULD silently drop QUIC-LB
packets with an incorrect token.
The Routing Bit Mask encodes a '1' at every bit position in the
server connection ID that will encode routing information.
These bits, along with the Modulus and Divisor, are chosen by the
load balancer as described in Section 3.1.
4.2.5. Encrypted CID Payload
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0x03 | CIDL (8) | SIDL (8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Token (64) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Server ID (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Key (128) +
| |
+ +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Encrypted CID Payload
The CIDL field is a one-octet unsigned integer that describes the
server connection ID length necessary to use this routing algorithm,
in octets.
The SIDL field is a one-octet unsigned integer that describes the
server ID length necessary to use this routing algorithm, in octets.
The server ID is the unique value assigned to the receiving server.
Its length is determined by the SIDL field.
The key is an 16-octet field that contains the key that the load
balancer will use to decrypt server IDs on QUIC packets. See
Section 6 to understand why sending keys in plaintext may be a safe
strategy.
4.2.6. Server ID Payload
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0x04 | SIDL (8) | Server ID (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Token (64) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Server ID Payload
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Load balancers send the Server ID when all global values for CID
encryption are sent out-of-band, so that only the server-unique
values must be sent in-band. The fields are identical to their
counterparts in the Encrypted CID payload.
4.2.7. Modulus Payload
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0x05 | Modulus (16) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Token (64) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Modulus Payload
Load balancers send the Modulus when all global values for Plaintext
CIDs are sent out-of-band, so that only the server- unique values
must be sent in-band. The Modulus field is identical to its
counterpart in the Routing Info payload.
5. Configuration Requirements
QUIC-LB strives to minimize the configuration load to enable, as much
as possible, a "plug-and-play" model. However, there are some
configuration requirements based on algorithm and protocol choices
above.
There are three levels of configuration that correspond to increasing
levels of concern about the security of the load balancer-server
path.
The complete information requirements are described in Section 4.
Load balancers MUST have configuration for all parameters of each
routing algorithm they support.
If there is any in-band communication, servers MUST be explicitly
configured with the token of the load balancer they expect to
interface with.
Optionally, servers MAY be configured with the global parameters of
supported routing algorithms. This allows load balancers to use
Server ID and Modulus Payloads, limiting the information sent in-
band.
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Finally, servers MAY be directly configured with their unique server
IDs or modulus, eliminating need for in-band messaging at all. In
this case, servers and load balancers MUST enable only one routing
algorithm, as there is no explicit message to agree on one or the
other.
6. Security Considerations
QUIC-LB is intended to preserve routability and prevent linkability.
Attacks on the protocol would compromise at least one of these
objectives.
A routability attack would inject QUIC-LB messages so that load
balancers incorrectly route QUIC connections.
A linkability attack would find some means of determining that two
connection IDs route to the same server. As described above, there
is no scheme that strictly prevents linkability for all traffic
patterns, and therefore efforts to frustrate any analysis of server
ID encoding have diminishing returns.
6.1. Outside attackers
For an outside attacker to break routability, it must inject packets
that correctly guess the 64-bit token, and servers must be reachable
from these outside hosts. Load balancers SHOULD drop QUIC-LB packets
that arrive on its external interface.
Off-path outside attackers cannot observe connection IDs, and will
therefore struggle to link them.
On-path outside attackers might try to link connection IDs to the
same QUIC connection. The Encrypted CID algorithm provides robust
entropy to making any sort of linkage. The Plaintext CID obscures
the mapping and prevents trivial brute-force attacks to determine the
routing parameters, but does not provide robust protection against
sophisticated attacks.
## Inside Attackers
As described above, on-path inside attackers are intrinsically able
to map two connection IDs to the same server. The QUIC-LB algorithms
do prevent the linkage of two connection IDs to the same individual
connection if servers make reasonable selections when generating new
IDs for that connection.
On-path inside attackers can break routability for new and migrating
connections by copying the token from QUIC-LB messages. From this
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privileged position, however, there are many other attacks that can
break QUIC connections to the server during the handshake.
Off-path inside attackers cannot observe connection IDs to link them.
To successfully break routability, they must correctly guess the
token.
7. IANA Considerations
There are no IANA requirements.
8. References
8.1. Normative References
[QUIC-TRANSPORT]
Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", draft-ietf-quic-
transport-14 (work in progress).
8.2. Informative References
[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>.
Appendix A. Acknowledgments
Appendix B. Change Log
*RFC Editor's Note:* Please remove this section prior to
publication of a final version of this document.
B.1. Since draft-duke-quic-load-balancers-00
o Converted to markdown
o Added variable length connection IDs
B.2. Since draft-duke-quic-load-balancers-01
o Complete rewrite
o Supports multiple security levels
o Lightweight messages
Duke Expires March 21, 2019 [Page 15]
Internet-Draft QUIC-LB September 2018
Author's Address
Martin Duke
F5 Networks, Inc.
Email: martin.h.duke@gmail.com
Duke Expires March 21, 2019 [Page 16]