SPRING Working Group R. Gandhi, Ed.
Internet-Draft C. Filsfils
Intended Status: Standards Track Cisco Systems, Inc.
Expires: November 16, 2019 D. Voyer
Bell Canada
M. Chen
Huawei
May 15, 2019
Performance Measurement Using TWAMP
for Segment Routing Networks
draft-gandhi-spring-twamp-srpm-01
Abstract
Segment Routing (SR) is applicable to both Multiprotocol Label
Switching (SR-MPLS) and IPv6 (SRv6) data planes. This document
specifies procedures for sending and processing synthetic probe query
and response messages for Performance Measurement (PM). The
procedure uses the mechanisms defined in RFC 5357 (Two-Way Active
Measurement Protocol (TWAMP)) for Delay Measurement, and also uses
the mechanisms specified in this document for direct-mode Loss
Measurement. The procedure specified is applicable to SR-MPLS and
SRv6 data planes for both links and end-to-end measurement for SR
Policies.
Status of This Memo
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Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 4
2.3. Reference Topology . . . . . . . . . . . . . . . . . . . . 4
3. Probe Messages . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Probe Query Message . . . . . . . . . . . . . . . . . . . 5
3.1.1. Delay Measurement Probe Query Message . . . . . . . . 6
3.1.1.1. Delay Measurement Message Checksum Complement . . 6
3.1.1.2. Delay Measurement Authentication Mode . . . . . . 7
3.1.2. Loss Measurement Probe Query Message . . . . . . . . . 7
3.1.2.1. Loss Measurement Message Checksum Complement . . . 10
3.1.2.2. Loss Measurement Authentication Mode . . . . . . . 10
3.1.3. Probe Query for SR Links . . . . . . . . . . . . . . . 10
3.1.4. Probe Query for End-to-end Measurement for SR Policy . 10
3.1.4.1. Probe Query Message for SR-MPLS Policy . . . . . . 10
3.1.4.2. Probe Query Message for SRv6 Policy . . . . . . . 11
3.2. Probe Response Message . . . . . . . . . . . . . . . . . . 12
3.2.1. One-way Measurement Mode . . . . . . . . . . . . . . . 14
3.2.2. Two-way Measurement Mode . . . . . . . . . . . . . . . 15
3.2.2.1. Return Path TLV . . . . . . . . . . . . . . . . . 15
3.2.2.2. Probe Response Message for SR-MPLS Policy . . . . 16
3.2.2.3. Probe Response Message for SRv6 Policy . . . . . . 17
3.2.3. Loopback Measurement Mode . . . . . . . . . . . . . . 17
4. Packet Loss Calculation . . . . . . . . . . . . . . . . . . . 17
5. Performance Measurement for P2MP SR Policies . . . . . . . . . 18
6. ECMP Support for SR Policies . . . . . . . . . . . . . . . . . 18
7. Security Considerations . . . . . . . . . . . . . . . . . . . 19
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
9.1. Normative References . . . . . . . . . . . . . . . . . . . 19
9.2. Informative References . . . . . . . . . . . . . . . . . . 20
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22
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1. Introduction
Segment Routing (SR) technology greatly simplifies network operations
for Software Defined Networks (SDNs). SR is applicable to both
Multiprotocol Label Switching (SR-MPLS) and IPv6 (SRv6) data planes.
SR takes advantage of the Equal-Cost Multipaths (ECMPs) between
source, transit and destination nodes. SR Policies as defined in
[I-D.spring-segment-routing-policy] are used to steer traffic through
a specific, user-defined path using a stack of Segments. Built-in SR
Performance Measurement (PM) is one of the essential requirements to
provide Service Level Agreements (SLAs).
The One-Way Active Measurement Protocol (OWAMP) defined in [RFC4656]
and Two-Way Active Measurement Protocol (TWAMP) defined in [RFC5357]
provide capabilities for the measurement of various performance
metrics in IP networks using synthetic probe messages. These
protocols rely on control channel signaling to establish a test
channel over an UDP path. These protocols lack support for
direct-mode Loss Measurement (LM) to detect actual data traffic loss
which is required in SR networks. The Simple Two-way Active
Measurement Protocol (STAMP) [I-D.ippm-stamp] alleviates the control
channel signaling by using configuration data model to provision test
channels and UDP ports. The TWAMP Light from broadband forum
[BBF.TR-390] provides simplified mechanisms for active performance
measurement in Customer Edge IP networks.
This document specifies procedures for sending and processing
synthetic probe query and response messages for Performance
Measurement. The procedure uses the mechanisms defined in RFC 5357
(Two-Way Active Measurement Protocol (TWAMP)) for Delay Measurement
(DM), and also uses the mechanisms specified in this document for
direct-mode Loss Measurement (LM). The procedure specified is
applicable to SR-MPLS and SRv6 data planes for both links and
end-to-end measurement for SR Policies. For SR Policies, there are
Equal Cost Multi-Paths (ECMP) between the source and transit nodes,
between transit nodes and between transit and destination nodes.
This document also defines mechanisms for handling ECMPs of SR
Policies for performance delay measurement.
2. Conventions Used in This Document
2.1. Requirements Language
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 [RFC2119] [RFC8174]
when, and only when, they appear in all capitals, as shown here.
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2.2. Abbreviations
BSID: Binding Segment ID.
DM: Delay Measurement.
ECMP: Equal Cost Multi-Path.
LM: Loss Measurement.
MPLS: Multiprotocol Label Switching.
NTP: Network Time Protocol.
OWAMP: One-Way Active Measurement Protocol.
PM: Performance Measurement.
PSID: Path Segment Identifier.
PTP: Precision Time Protocol.
SID: Segment ID.
SL: Segment List.
SR: Segment Routing.
SR-MPLS: Segment Routing with MPLS data plane.
SRv6: Segment Routing with IPv6 data plane.
STAMP: Simple Two-way Active Measurement Protocol.
TC: Traffic Class.
TWAMP: Two-Way Active Measurement Protocol.
2.3. Reference Topology
In the reference topology, the querier node R1 initiates a probe
query for performance measurement and the responder node R5 sends a
probe response for the query message received. The probe response
may be sent to the querier node R1. The nodes R1 and R5 may be
directly connected via a link enabled with Segment Routing or there
exists a Point-to-Point (P2P) SR Policy
[I-D.spring-segment-routing-policy] on node R1 with destination to
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node R5. In case of Point-to-Multipoint (P2MP), SR Policy
originating from source node R1 may terminate on multiple destination
leaf nodes [I-D.spring-sr-p2mp-policy].
+-------+ Query +-------+
| | - - - - - - - - - ->| |
| R1 |---------------------| R5 |
| |<- - - - - - - - - - | |
+-------+ Response +-------+
Reference Topology
For delay and loss measurements, for both links and end-to-end SR
Policies, no PM session is created on the responder node R5. One-way
delay and two-way delay measurements are defined in [RFC4656] and
[RFC5357], respectively. One-way loss measurement provides receive
packet loss whereas two-way loss measurement provides both transmit
and receive packet loss.
For Performance Measurement, synthetic probe query and response
messages are used as following:
o For Delay Measurement, the probe messages are sent on the
congruent path of the data traffic by the querier node, and are
used to measure the delay experienced by the actual data traffic
flowing on the links and SR Policies.
o For Loss Measurement, the probe messages are sent on the congruent
path of the data traffic by the querier node, and are used to
collect the receive traffic counters for the incoming link or
incoming SID where the probe query messages are received at the
responder node (incoming link or incoming SID used as the
responder node has no PM session state present).
The In-Situ Operations, Administration, and Maintenance (IOAM)
mechanisms for SR-MPLS defined in [I-D.spring-ioam-sr-mpls] and for
SRv6 defined in [I-D.spring-srv6-oam] are used to carry PM
information in-band as part of the data traffic, and are outside the
scope of this document.
3. Probe Messages
3.1. Probe Query Message
In this document, the probe messages defined in [RFC5357] are used
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for Delay and Loss measurements for SR links and end-to-end SR
Policies. The user-configured UDP ports (separate UDP port for each
message format) are used for identifying the PM probe packets and to
avoid signaling to bootstrap PM sessions. This approach is similar
to the one defined in STAMP protocol [I-D.ippm-stamp]. The IPv4 TTL
or IPv6 Hop Limit field of the IP header MUST be set to 255.
3.1.1. Delay Measurement Probe Query Message
The message content for Delay Measurement probe query message using
UDP header [RFC768] is shown in Figure 1. The DM probe query message
is sent with user-configured Destination UDP port number for DM. The
Destination UDP port cannot be used as Source port, since the message
does not have any indication to distinguish between query and
response. The DM probe query message contains the payload for delay
measurement defined in Section 4.1.2 of OWAMP [RFC4656]. As an
alternative, the DM probe query message contains the payload defined
in Section 4.2.1 of TWAMP [RFC5357].
+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Querier IPv4 or IPv6 Address .
. Destination IP Address = Responder IPv4 or IPv6 Address .
. Protocol = UDP .
. Router Alert Option Not Set .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Querier .
. Destination Port = User-configured Port for Delay Measurement.
. .
+---------------------------------------------------------------+
| Payload = Message as specified in Section 4.2.1 of RFC 5357 |
| | Payload = Message as specified in Section 4.1.2 of RFC 4656 |
. .
+---------------------------------------------------------------+
Figure 1: DM Probe Query Message
Timestamp field is eight bytes. It is recommended to use the IEEE
1588v2 Precision Time Protocol (PTP) truncated 64-bit timestamp
format [IEEE1588] using the procedure defined in [RFC8186].
3.1.1.1. Delay Measurement Message Checksum Complement
The Checksum Complement shown in Figure 3 for OWAMP in [RFC7820] and
Figure 4 for TWAMP in [RFC7820] for delay measurement message format
follows the procedure defined in [RFC7820] and can be used optionally
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with the procedures defined in this document.
3.1.1.2. Delay Measurement Authentication Mode
When using the authenticated mode for delay measurement, the matching
authentication type (e.g. HMAC-SHA-256) and key are user-configured
on both the querier and responder nodes. A different user-configured
destination UDP port is required for the delay measurement in
authentication mode due to the different probe message format.
3.1.2. Loss Measurement Probe Query Message
The message content for Loss Measurement probe query message using
UDP header [RFC768] is shown in Figure 2. The LM probe query message
is sent with user-configured Destination UDP port number for LM.
Different Destination UDP ports are used for direct-mode and
inferred-mode loss measurements. The Destination UDP port cannot be
used as Source port, since the message does not have any indication
to distinguish between query and response. The LM probe query
message contains the payload for loss measurement as defined in
Figure 2. An alternative, the LM probe query message contains the
payload defined in Figure 8.
Both of these LM message formats define fixed locations for the
counters in the payload and are easy to implement in hardware. In
addition, new LM messages do not require any backwards compatibility
or support for the existing DM message formats in [RFC5357].
+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Querier IPv4 or IPv6 Address .
. Destination IP Address = Responder IPv4 or IPv6 Address .
. Protocol = UDP .
. Router Alert Option Not Set .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Querier .
. Destination Port = User-configured Port for Loss Measurement .
. .
+---------------------------------------------------------------+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transmit Counter |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender TTL |X|B|0|0|0|0|0|0| Block Number |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Packet Padding .
. .
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Checksum Complement |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2A: LM Probe Query Message for OWAMP
+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Querier IPv4 or IPv6 Address .
. Destination IP Address = Responder IPv4 or IPv6 Address .
. Protocol = UDP .
. Router Alert Option Not Set .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Querier .
. Destination Port = User-configured Port for Loss Measurement .
. .
+---------------------------------------------------------------+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (12 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transmit Counter |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (8 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender TTL |X|B|0|0|0|0|0|0| Block Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (12 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HMAC (16 octets) |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
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. Packet Padding .
. .
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Checksum Complement |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2B: LM Probe Query Message for OWAMP - Authenticated Mode
Sequence Number (32-bit): As defined in [RFC5357].
Transmit Counter (64-bit): The number of packets sent by the querier
node in the query message and by the responder node in the response
message. The counter is always written at the fixed location in the
probe query and response messages.
Receive Counter (64-bit): The number of packets received at the
responder node. It is written by the responder node in the probe
response message.
Sender Counter (64-bit): This is the exact copy of the transmit
counter from the received query message. It is written by the
responder node in the probe response message.
Sender Sequence Number (32-bit): As defined in [RFC5357].
Sender TTL: As defined in [RFC5357].
Flag: The meanings of the Flag bits are:
X: Extended counter format indicator. Indicates the use of
extended (64-bit) counter values. Initialized to 1 upon creation
(and prior to transmission) of an LM Query and copied from an LM
Query to an LM response. Set to 0 when the LM message is
transmitted or received over an interface that writes 32-bit
counter values.
B: Octet (byte) count. When set to 1, indicates that the Counter
1-4 fields represent octet counts. The octet count applies to all
packets within the LM scope, and the octet count of a packet sent
or received over a channel includes the total length of that
packet (but excludes headers, labels, or framing of the channel
itself). When set to 0, indicates that the Counter fields
represent packet counts.
0: Set to 0.
Block Number (16-bit): The Loss Measurement using Alternate-Marking
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method defined in [RFC8321] requires to identify the Block Number (or
color) of the traffic counters. The probe query and response
messages carry Block Number for the traffic counters for loss
measurement. In both probe query and response messages, the counters
MUST belong to the same Block Number.
HMAC: The PM probe packet in authenticated mode includes a key Hashed
Message Authentication Code (HMAC) ([RFC2104]) hash. Each probe
query and response messages are authenticated by adding Sequence
Number with Hashed Message Authentication Code (HMAC) TLV. It can
use HMAC-SHA-256 truncated to 128 bits (similarly to the use of it in
IPSec defined in [RFC4868]); hence the length of the HMAC field is 16
octets.
HMAC uses own key and the definition of the mechanism to distribute
the HMAC key is outside the scope of this document.
In authenticated mode, only the sequence number is encrypted, and the
other payload fields are sent in clear text. The probe packet MAY
include Comp.MBZ (Must Be Zero) variable length field to align the
packet on 16 octets boundary.
3.1.2.1. Loss Measurement Message Checksum Complement
The Checksum Complement shown in Figure 2 for loss measurement
message format follows the procedure defined in [RFC7820] and can be
used optionally with the procedures defined in this document.
3.1.2.2. Loss Measurement Authentication Mode
When using the authenticated mode for loss measurement, the matching
authentication type (e.g. HMAC-SHA-256) and key are user-configured
on both the querier and responder nodes. A different user-configured
destination UDP port is required for the loss measurement in
authentication mode due to the different message format.
3.1.3. Probe Query for SR Links
The probe query message as defined in Figure 1 is sent on the
congruent path of the data traffic for Delay measurement. The probe
query message as defined in Figure 2 is sent on the congruent path of
the data traffic for Loss measurement.
3.1.4. Probe Query for End-to-end Measurement for SR Policy
3.1.4.1. Probe Query Message for SR-MPLS Policy
The message content for the probe query message using UDP header for
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end-to-end performance measurement of SR-MPLS Policy is shown in
Figure 3.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment List(1) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment List(n) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSID | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message as shown in Figure 1 for DM or Figure 2 for LM |
. .
+---------------------------------------------------------------+
Figure 3: Probe Query Message for SR-MPLS Policy
The Segment List (SL) can be empty to indicate Implicit NULL label
case.
The Path Segment Identifier (PSID) [I-D.spring-mpls-path-segment] of
the SR-MPLS Policy is used for accounting received traffic on the
egress node for loss measurement. The PSID is not required for
end-to-end SR Policy delay measurement.
3.1.4.2. Probe Query Message for SRv6 Policy
An SRv6 Policy setup using the SRv6 Segment Routing Header (SRH) and
a Segment List as defined in [I-D.6man-segment-routing-header]. The
probe query messages using UDP header for end-to-end performance
measurement of an SRv6 Policy is sent using its SRv6 Segment Routing
Header (SRH) and Segment List as shown in Figure 4.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRH |
. END.OTP (DM) or END.OP (LM) with Target SRv6 SID .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message as shown in Figure 1 for DM or Figure 2 for LM |
. (Using IPv6 Addresses) .
. .
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+---------------------------------------------------------------+
Figure 4: Probe Query Message for SRv6 Policy
For delay measurement of SRv6 Policy using SRH, END function END.OTP
[I-D.spring-srv6-oam] is used with the target SRv6 SID to punt probe
messages on the target node, as shown in Figure 4. Similarly, for
loss measurement of SRv6 Policy, END function END.OP
[I-D.spring-srv6-oam] is used with target SRv6 SID to punt probe
messages on the target node.
3.2. Probe Response Message
The probe response message is sent using the IP/UDP information from
the probe query message. The content of the probe response message
is shown in Figure 5.
+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Responder IPv4 or IPv6 Address .
. Destination IP Address = Source IP Address from Query .
. Protocol = UDP .
. Router Alert Option Not Set .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Responder .
. Destination Port = Source Port from Query .
. .
+---------------------------------------------------------------+
| DM Payload as specified in Section 4.2.1 of RFC 5357, or |
. LM Payload as specified in Figure 8 in this document .
. .
+---------------------------------------------------------------+
Figure 5: Probe Response Message
+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Querier IPv4 or IPv6 Address .
. Destination IP Address = Responder IPv4 or IPv6 Address .
. Protocol = UDP .
. Router Alert Option Not Set .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Querier .
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. Destination Port = User-configured Port for Loss Measurement .
. .
+---------------------------------------------------------------+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transmit Counter |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receive Counter |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Counter |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender TTL |X|B|0|0|0|0|0|0| Block Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Packet Padding .
. .
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Checksum Complement |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8A: LM Probe Response Message for TWAMP
+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Querier IPv4 or IPv6 Address .
. Destination IP Address = Responder IPv4 or IPv6 Address .
. Protocol = UDP .
. Router Alert Option Not Set .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Querier .
. Destination Port = User-configured Port for Loss Measurement .
. .
+---------------------------------------------------------------+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (12 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Transmit Counter |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (8 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receive Counter |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (8 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (12 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Counter |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (8 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender TTL |X|B|0|0|0|0|0|0| Block Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (12 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HMAC (16 octets) |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Packet Padding .
. .
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Checksum Complement |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8B: LM Probe Response Message for TWAMP - Authenticated Mode
3.2.1. One-way Measurement Mode
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In one-way performance measurement mode, the probe response message
as defined in Figure 5 is sent for both SR links and SR Policies.
3.2.2. Two-way Measurement Mode
In two-way performance measurement mode, when using a bidirectional
path, the probe response message as defined in Figure 5 is sent back
on the congruent path of the data traffic to the querier node.
3.2.2.1. Return Path TLV
For two-way performance measurement, the responder node needs to send
the probe response message on a specific reverse SR path. This way
the destination node does not require any additional SR Policy state.
The querier node can request in the probe query message to the
responder node to send a response back on a given reverse path
(typically co-routed path for two-way measurement).
[I-D.ippm-stamp-option-tlv] defines STAMP probe query messages that
can include one or more optional TLVs. New TLV Type (TBA1) is
defined in this document for Return Path to carry reverse SR path for
probe response messages (in the payload of the message). The format
of the Return Path TLV is shown in Figure 8A and 8B:
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 = TBA1 | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Return Path Sub-TLVs |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8A: Return Path TLV
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 | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment List(1) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Segment List(n) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8B: Segment List Sub-TLV in Return Path TLV
The Sub-TLV in the Return Path TLV can be one of the following Types:
o Type (value 1): SR-MPLS Label Stack of the Reverse SR Policy
o Type (value 2): SR-MPLS Binding SID [I-D.pce-binding-label-sid] of
the Reverse SR Policy
o Type (value 3): SRv6 Segment List of the Reverse SR Policy
o Type (value 4): SRv6 Binding SID [I-D.pce-binding-label-sid] of
the Reverse SR Policy
With sub-TLV Type 1, the Segment List(1) can be used by the responder
node to compute the next-hop IP address and outgoing interface to
send the probe response messages.
The Return Path TLV is optional. The PM querier node MUST only
insert one Return Path TLV in the probe query message and the
responder node MUST only process the first Return Path TLV in the
probe query message and ignore other Return Path TLVs if present.
The responder node MUST send probe response message back on the
reverse path specified in the Return Path TLV and MUST NOT add Return
Path TLV in the probe response message.
3.2.2.2. Probe Response Message for SR-MPLS Policy
The message content for sending probe response message using the UDP
header for two-way end-to-end performance measurement of an SR-MPLS
Policy is shown in Figure 6.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment List(1) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment List(n) | TC |S| TTL |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message as shown in Figure 5 |
. .
+---------------------------------------------------------------+
Figure 6: Probe Response Message for SR-MPLS Policy
The Path Segment Identifier (PSID) [I-D.spring-mpls-path-segment] of
the forward SR Policy can be used to find the reverse SR Policy to
send the probe response message for two-way measurement of SR Policy.
3.2.2.3. Probe Response Message for SRv6 Policy
The message content for sending probe response message on the
congruent path of the data traffic using UDP header for two-way
end-to-end performance measurement of an SRv6 Policy with SRH is
shown in Figure 7.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRH |
. END.OTP (DM) or END.OP (LM) with Target SRv6 SID .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message as shown in Figure 5 (with IPv6 Addresses) |
. .
+---------------------------------------------------------------+
Figure 7: Probe Response Message for SRv6 Policy
3.2.3. Loopback Measurement Mode
The Loopback measurement mode can be used to measure round-trip delay
for a bidirectional Path. The probe query messages in this case
either carry the reverse Path information as part of the SR header or
set the querier address as the destination address in the IP header.
The responder node does not process the PM probe messages and
generate response messages.
4. Packet Loss Calculation
The formula for calculating the one-way packet loss using packet
counters for a given block number is as following:
One-way Packet_Loss[n-1, n]
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= (Sender_Counter[n] - Sender_Counter[n-1])
- (Receive_Counter[n] - Receive_Counter[n-1])
5. Performance Measurement for P2MP SR Policies
The procedures for delay and loss measurement described in this
document for Point-to-Point (P2P) SR Policies
[I-D.spring-segment-routing-policy] are also equally applicable to
the Point-to-Multipoint (P2MP) SR Policies
[I-D.spring-sr-p2mp-policy] as following:
o The querier root node sends probe query messages using the either
Spray P2MP segment or TreeSID P2MP segment defined in
[I-D.spring-sr-p2mp-policy] over the P2MP SR Policy.
o Each responder leaf node sends its IP address in the Source
Address of the probe response messages. This allows the querier
root node to identify the responder leaf nodes of the P2MP SR
Policy.
o The P2MP root node measures the end-to-end delay and loss
performance for each P2MP leaf node.
6. ECMP Support for SR Policies
An SR Policy can have ECMPs between the source and transit nodes,
between transit nodes and between transit and destination nodes.
Usage of Anycast SID [RFC8402] by an SR Policy can result in ECMP
paths via transit nodes part of that Anycast group. The PM probe
messages need to be sent to traverse different ECMP paths to measure
performance delay of an SR Policy.
Forwarding plane has various hashing functions available to forward
packets on specific ECMP paths. Following mechanisms can be used in
PM probe messages to take advantage of the hashing function in
forwarding plane to influence the path taken by them.
o The mechanisms described in [RFC8029] and [RFC5884] for handling
ECMPs are also applicable to the performance measurement. In the
IP/UDP header of the PM probe messages, Destination Addresses in
127/8 range for IPv4 or 0:0:0:0:0:FFFF:7F00/104 range for IPv6 can
be used to exercise a particular ECMP path. As specified in
[RFC6437], 3-tuple of Flow Label, Source Address and Destination
Address fields in the IPv6 header can also be used.
o For SR-MPLS Policy, entropy label [RFC6790] can be used in the PM
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probe messages.
o For SRv6 Policy using SRH, Flow Label in the SRH
[I-D.6man-segment-routing-header] of the PM probe messages can be
used.
7. Security Considerations
The performance measurement is intended for deployment in
well-managed private and service provider networks. As such, it
assumes that a node involved in a measurement operation has
previously verified the integrity of the path and the identity of the
far end responder node.
If desired, attacks can be mitigated by performing basic validation
and sanity checks, at the querier, of the counter or timestamp fields
in received measurement response messages. The minimal state
associated with these protocols also limits the extent of measurement
disruption that can be caused by a corrupt or invalid message to a
single query/response cycle.
Use of HMAC-SHA-256 in the authenticated mode protects the data
integrity of the probe messages. SRv6 has HMAC protection
authentication defined for SRH [I-D.6man-segment-routing-header].
Hence, PM probe messages for SRv6 may not need authentication mode.
Cryptographic measures may be enhanced by the correct configuration
of access-control lists and firewalls.
8. IANA Considerations
IANA is requested to allocate values for the following Return Path
TLV Type for [I-D.ippm-stamp-option-tlv] to be carried in PM probe
query messages:
o Type TBA1: Return Path TLV
9. References
9.1. Normative References
[RFC768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
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Requirement Levels", RFC 2119, March 1997.
[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, September 2006.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, October 2008.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", RFC 8174, May 2017.
[I-D.spring-srv6-oam] Ali, Z., et al., "Operations, Administration,
and Maintenance (OAM) in Segment Routing Networks with
IPv6 Data plane (SRv6)", draft-ali-spring-srv6-oam, work
in progress.
[I-D.ippm-stamp-option-tlv] Mirsky, G., et al., "Simple Two-way
Active Measurement Protocol Optional Extensions",
draft-mirsky-ippm-stamp-option-tlv, work in progress.
9.2. Informative References
[IEEE1588] IEEE, "1588-2008 IEEE Standard for a Precision Clock
Synchronization Protocol for Networked Measurement and
Control Systems", March 2008.
[RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
"Bidirectional Forwarding Detection (BFD) for MPLS Label
Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884,
June 2010.
[RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme,
"IPv6 Flow Label Specification", RFC 6437, November 2011.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, November 2012.
[RFC7820] Mizrahi, T., "UDP Checksum Complement in the One-Way
Active Measurement Protocol (OWAMP) and Two-Way Active
Measurement Protocol (TWAMP)", RFC 7820, March 2016.
[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Kumar, N.,
Aldrin, S. and M. Chen, "Detecting Multiprotocol Label
Switched (MPLS) Data-Plane Failures", RFC 8029, March
2017.
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[RFC8186] Mirsky, G., and I. Meilik, "Support of the IEEE 1588
Timestamp Format in a Two-Way Active Measurement Protocol
(TWAMP)", RFC 8186, June 2017.
[RFC8321] Fioccola, G. Ed., "Alternate-Marking Method for Passive
and Hybrid Performance Monitoring", RFC 8321, January
2018.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[I-D.spring-segment-routing-policy] Filsfils, C., et al., "Segment
Routing Policy Architecture",
draft-ietf-spring-segment-routing-policy, work in
progress.
[I-D.spring-sr-p2mp-policy] Voyer, D. Ed., et al., "SR Replication
Policy for P2MP Service Delivery",
draft-voyer-spring-sr-p2mp-policy, work in progress.
[I-D.spring-mpls-path-segment] Cheng, W., et al., "Path Segment in
MPLS Based Segment Routing Network",
draft-ietf-spring-mpls-path-segment, work in progress.
[] Filsfils, C., et al., "IPv6
Segment Routing Header (SRH)",
draft-ietf-6man-segment-routing-header, work in progress.
[I-D.ippm-stamp] Mirsky, G. et al. "Simple Two-way Active
Measurement Protocol", draft-ietf-ippm-stamp, work in
progress.
[I-D.pce-binding-label-sid] Filsfils, C., et al., "Carrying Binding
Label Segment-ID in PCE-based Networks",
draft-sivabalan-pce-binding-label-sid, work in progress.
[BBF.TR-390] "Performance Measurement from IP Edge to Customer
Equipment using TWAMP Light", BBF TR-390, May 2017.
[I-D.spring-ioam-sr-mpls] Gandhi, R. Ed., et al., "Segment Routing
with MPLS Data Plane Encapsulation for In-situ OAM Data",
draft-gandhi-spring-ioam-sr-mpls, work in progress.
[RFC2104] Krawczyk, H., Bell-are, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104, February
1997.
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[RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-
384, and HMAC-SHA-512 with IPsec", RFC 4868, May 2007.
Acknowledgments
The authors would like to thank Thierry Couture for various
discussions on the use-cases for TWAMP in segment routing. The
authors would also like to thank Greg Mirsky for reviewing this
document and providing useful comments and suggestions.
Authors' Addresses
Rakesh Gandhi (editor)
Cisco Systems, Inc.
Canada
Email: rgandhi@cisco.com
Clarence Filsfils
Cisco Systems, Inc.
Email: cfilsfil@cisco.com
Daniel Voyer
Bell Canada
Email: daniel.voyer@bell.ca
Mach(Guoyi) Chen
Huawei
Email: mach.chen@huawei.com
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