MPLS Working Group R. Gandhi, Ed.
Internet-Draft C. Filsfils
Intended Status: Standards Track Cisco Systems, Inc.
Expires: June 6, 2020 D. Voyer
Bell Canada
S. Salsano
Universita di Roma "Tor Vergata"
M. Chen
Huawei
December 4, 2019
Performance Measurement for
Segment Routing Networks with MPLS Data Plane
draft-gandhi-mpls-rfc6374-sr-01
Abstract
Segment Routing (SR) leverages the source routing paradigm. RFC 6374
specifies protocol mechanisms to enable the efficient and accurate
measurement of packet loss, one-way and two-way delay, as well as
related metrics such as delay variation in MPLS networks using probe
messages. This document utilizes these mechanisms for Performance
Delay and Loss Measurements in Segment Routing (SR) networks with
MPLS data plane (SR-MPLS), for both SR links and end-to-end SR
Policies. In addition, this document defines Return Path TLV for
two-way performance measurement and Block Number TLV for loss
measurement.
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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Task Force (IETF). Note that other groups may also distribute
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and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
Copyright Notice
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Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 4
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 4
2.3. Reference Topology . . . . . . . . . . . . . . . . . . . . 5
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Probe Query and Response Packets . . . . . . . . . . . . . . . 6
4.1. Probe Packet Header for SR-MPLS Policies . . . . . . . . . 6
4.2. Probe Packet Header for SR-MPLS Links . . . . . . . . . . 7
4.3. Probe Response Message for SR-MPLS Links and Policies . . 7
4.3.1. One-way Measurement Mode . . . . . . . . . . . . . . . 7
4.3.2. Two-way Measurement Mode . . . . . . . . . . . . . . . 7
4.3.3. Loopback Measurement Mode . . . . . . . . . . . . . . 8
4.4. Return Path TLV . . . . . . . . . . . . . . . . . . . . . 8
5. Performance Delay Measurement . . . . . . . . . . . . . . . . 9
5.1. Delay Measurement Message Format . . . . . . . . . . . . . 9
5.2. Timestamps . . . . . . . . . . . . . . . . . . . . . . . . 10
6. Performance Loss Measurement . . . . . . . . . . . . . . . . . 10
6.1. Loss Measurement Message Format . . . . . . . . . . . . . 11
6.2. Block Number TLV . . . . . . . . . . . . . . . . . . . . . 11
7. Performance Measurement for P2MP SR Policies . . . . . . . . . 11
8. ECMP for SR-MPLS Policies . . . . . . . . . . . . . . . . . . 12
9. SR Link Extended TE Metrics Advertisements . . . . . . . . . . 13
10. Security Considerations . . . . . . . . . . . . . . . . . . . 13
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
12.1. Normative References . . . . . . . . . . . . . . . . . . 14
12.2. Informative References . . . . . . . . . . . . . . . . . 14
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 17
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
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1. Introduction
Service provider's ability to satisfy Service Level Agreements (SLAs)
depend on the ability to measure and monitor performance metrics for
packet loss and one-way and two-way delay, as well as related metrics
such as delay variation. The ability to monitor these performance
metrics also provides operators with greater visibility into the
performance characteristics of their networks, thereby facilitating
planning, troubleshooting, and network performance evaluation.
Segment Routing (SR) leverages the source routing paradigm and
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 and transit nodes,
between transit nodes and between 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 paths using a stack
of Segments. Built-in SR Performance Measurement (PM) is one of the
essential requirements to provide Service Level Agreements (SLAs).
[RFC6374] specifies protocol mechanisms to enable the efficient and
accurate measurement of performance metrics in MPLS networks using
probe messages. 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. However, mechanisms
defined in [RFC6374] are more suitable for Segment Routing (SR) when
using MPLS data plane (SR-MPLS). [RFC6374] also supports IEEE 1588
timestamps [IEEE1588] and "direct mode" Loss Measurement (LM), which
are required in SR networks.
[RFC7876] specifies the procedures to be used when sending and
processing out-of-band performance measurement probe replies over an
UDP return path when receiving RFC 6374 based probe queries. These
procedures can be used to send out-of-band PM replies for both
SR-MPLS links and Policies [I-D.spring-segment-routing-policy] for
one-way measurement.
This document utilizes the probe-based mechanisms defined in
[RFC6374] for Performance Delay and Loss Measurements in SR networks
with MPLS data plane, for both SR links and end-to-end SR Policies.
In addition, this document defines Return Path TLV for two-way
performance measurement and Block Number TLV for loss measurement.
The Performance Measurements (PM) for SR links are used to compute
extended Traffic Engineering (TE) metrics for delay and loss and can
be advertised in the network using the routing protocol extensions.
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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.
2.2. Abbreviations
ACH: Associated Channel Header.
DM: Delay Measurement.
ECMP: Equal Cost Multi-Path.
G-ACh: Generic Associated Channel (G-ACh).
GAL: Generic Associated Channel (G-ACh) Label.
LM: Loss Measurement.
MPLS: Multiprotocol Label Switching.
NTP: Network Time 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.
TC: Traffic Class.
TE: Traffic Engineering.
URO: UDP Return Object.
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2.3. Reference Topology
In the reference topology shown in Figure 1, the sender node R1
initiates a performance measurement probe query and the responder
node R5 sends a probe response for the query message received. The
probe response is typically sent back to the sender 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
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 +-------+
Sender Responder
Figure 1: Reference Topology
3. Overview
One-way delay and two-way delay measurement procedure defined in
Section 2.4 of [RFC6374] are used. Transmit and Receive packet loss
measurement procedures defined in Section 2.2 and Section 2.6 of
[RFC6374] are used. One-way loss measurement provides receive packet
loss whereas two-way loss measurement provides both transmit and
receive packet loss. For both links and end-to-end SR Policies, no
PM session for delay or loss measurement is created on the responder
node R5 [RFC6374].
For Performance Measurement, probe query and response messages are
sent as following:
o For Delay Measurement, the probe messages are sent on the
congruent path of the data traffic by the sender 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 sender 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 needed since the
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responder node does not have PM session state present).
o For SR Policy performance measurement, in order to ensure that the
probe query message is processed by the intended responder node,
destination address TLV [RFC6374] can be sent in the probe query
message. The responder node only replies if it is the intended
destination for the probe query.
The In-Situ Operations, Administration, and Maintenance (IOAM)
mechanisms for SR-MPLS defined in [I-D.mpls-ioam-sr] are used to
carry PM information in-band as part of the data traffic packets, and
are outside the scope of this document.
4. Probe Query and Response Packets
4.1. Probe Packet Header for SR-MPLS Policies
As described in Section 2.9.1 of [RFC6374], MPLS PM probe query and
response messages flow over the MPLS Generic Associated Channel
(G-ACh). A probe packet for an end-to-end measurement for SR Policy
contains SR-MPLS label stack [I-D.spring-segment-routing-policy],
with the G-ACh Label (GAL) at the bottom of the stack (with S=1).
The GAL is followed by an Associated Channel Header (ACH), which
identifies the message type, and the message payload following the
ACH as shown in Figure 2.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label(1) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label(n) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GAL (value 13) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Reserved | GAL Channel Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Probe Packet Header for an End-to-end SR-MPLS Policy
The SR-MPLS label stack can be empty (as shown in Figure 3) to
indicate Implicit NULL label case.
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4.2. Probe Packet Header for SR-MPLS Links
As described in Section 2.9.1 of [RFC6374], MPLS PM probe query and
response messages flow over the MPLS Generic Associated Channel
(G-ACh). A probe packet for SR-MPLS links contains G-ACh Label (GAL)
(with S=1). The GAL is followed by an Associated Channel Header
(ACH), which identifies the message type, and the message payload
following the ACH as 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GAL (value 13) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Reserved | GAL Channel Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Probe Packet Header for an SR-MPLS Link
4.3. Probe Response Message for SR-MPLS Links and Policies
4.3.1. One-way Measurement Mode
In one-way performance measurement mode [RFC7679], the PM sender node
can receive "out-of-band" probe replies by properly setting the UDP
Return Object (URO) TLV in the probe query message. The URO TLV
(Type=131) is defined in [RFC7876] and includes the
UDP-Destination-Port and IP Address. In particular, if the sender
sets its own IP address in the URO TLV, the probe response is sent
back by the responder node to the sender node. In addition, the
"control code" in the probe query message is set to "out-of-band
response requested".
4.3.2. Two-way Measurement Mode
In two-way performance measurement mode [RFC6374], when using a
bidirectional path, the probe response message is sent back to the
sender node on the congruent path of the data traffic on the reverse
direction SR Link or associated SR Policy [I-D.bidir-sr] using a
message with format similar to their probe query message. In this
case, the "control code" in the probe query message is set to "in-
band response requested".
A Path Segment Identifier (PSID) [I-D.spring-mpls-path-segment] of
the forward SR-MPLS Policy can be used to find the associated reverse
SR-MPLS Policy [I-D.bidir-sr] and to send back the probe response
message for two-way measurement.
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4.3.3. Loopback Measurement Mode
The Loopback measurement mode defined in Section 2.8 of [RFC6374] can
be used to measure round-trip delay for a bidirectional SR Path
[I-D.bidir-sr]. The probe query messages in this case carries the
reverse SR Path label stack as part of the MPLS header. The GAL is
still carried at the bottom of the label stack (with S=1). The
responder node does not process the PM probe messages and generate
response messages.
4.4. Return Path TLV
For two-way performance measurement, the responder node needs to send
the probe response message on a specific reverse path. The sender
node can request in the probe query message to the responder node to
send a response message back on a given reverse path (e.g. co-routed
path for two-way measurement). This way the destination node does
not require any additional SR Policy state.
For one-way performance measurement, the sender node address may not
be reachable via IP route from the responder node. The sender node
in this case needs to send its reachability path information to the
responder node.
[RFC6374] defines DM and LM 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 path for probe response
messages (in the payload of the message). The format of the Return
Path TLV is shown in Figure 4A and 4B:
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 4A: 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Label(1) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label(n) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4B: Segment List Sub-TLV in Return Path TLV
The Segment List 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 Path
o Type (value 2): SR-MPLS Binding SID [I-D.pce-binding-label-sid] of
the Reverse SR Policy
The Return Path TLV is optional. The PM sender 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. In the absence of Return Path TLV, in
two-way measurement mode, the probe response message is sent back on
the incoming physical interface where the probe query message is
received.
5. Performance Delay Measurement
5.1. Delay Measurement Message Format
As defined in [RFC6374], MPLS DM probe query and response messages
use Associated Channel Header (ACH) (value 0x000C for delay
measurement) [RFC6374], which identifies the message type, and the
message payload following the ACH. For both SR links and end-to-end
measurement for SR-MPLS Policies, the same MPLS DM ACH value is used.
The DM message payload as defined in Section 3.2 of [RFC6374] is used
for SR-MPLS delay measurement, for both SR links and end-to-end SR
Policies.
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5.2. Timestamps
The Section 3.4 of [RFC6374] defines timestamp format that can be
used for delay measurement. The IEEE 1588 Precision Time Protocol
(PTP) timestamp format [IEEE1588] is used by default as described in
Appendix A of [RFC6374], preferred with hardware support in Segment
Routing networks.
Note that for one-way delay measurement mode, clock synchronization
between the sender and responder nodes is required. The two-way
delay measurement mode and loopback measurement mode do not require
clock synchronization between the sender and responder nodes.
6. Performance Loss Measurement
The LM protocol can perform two distinct kinds of loss measurement as
described in Section 2.9.8 of [RFC6374].
o In inferred mode, LM will measure the loss of specially generated
test messages in order to infer the approximate data plane loss
level. Inferred mode LM provides only approximate loss
accounting.
o In direct mode, LM will directly measure data plane packet loss.
Direct mode LM provides perfect loss accounting, but may require
hardware support.
For both of these modes of LM, Path Segment Identifier (PSID)
[I-D.spring-mpls-path-segment] is used for accounting received
traffic on the egress node of the SR-MPLS Policy as shown in Figure
5. Different values of PSID can be used to measure packet loss per
SR-MPLS Policy, per Candidate Path or per Segment List of the SR
Policy.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSID | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GAL (value 13) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Reserved | GAL Channel Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: With Path Segment Identifier for SR-MPLS Policy
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6.1. Loss Measurement Message Format
As defined in [RFC6374], MPLS LM probe query and response messages
use Associated Channel Header (ACH) (value 0x000A for direct loss
measurement or value 0x000B for inferred loss measurement), which
identifies the message type, and the message payload following the
ACH. For both SR links and end-to-end measurement for SR-MPLS
Policies, the same MPLS LM ACH value is used.
The LM message payload as defined in Section 3.1 of [RFC6374] is used
for SR-MPLS loss measurement, for both SR links and end-to-end SR
Policies.
6.2. Block Number TLV
The Loss Measurement using Alternate-Marking method defined in
[RFC8321] requires to color the data traffic. To be able to compare
the transmit and receive traffic counters of the matching color, the
Block Number (or color) of the traffic counters is carried by the
probe query and response messages for loss measurement. Probe query
and response messages specified in [RFC6374] for Loss Measurement do
not identify the Block Number of the counters.
[RFC6374] defines probe query and response messages that can include
one or more optional TLVs. New TLV Type (value TBA2) is defined in
this document to carry the Block Number (8-bit) of the traffic
counters in the probe query and response messages for loss
measurement. The format of the Block Number TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type TBA2 | Length | Reserved | Block Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Block Number TLV
The Block Number TLV is optional. The PM sender node SHOULD only
insert one Block Number TLV in the probe query message and the
responder node in the probe response message SHOULD return the first
Block Number TLV from the probe query messages and ignore other Block
Number TLVs if present. In probe messages, the counters MUST belong
to the same Block Number.
7. Performance Measurement for P2MP SR Policies
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The procedures for delay and loss measurement described in this
document for Point-to-Point (P2P) SR-MPLS Policies
[I-D.spring-segment-routing-policy] are also equally applicable to
the Point-to-Multipoint (P2MP) SR-MPLS Policies
[I-D.spring-sr-p2mp-policy] as following:
o The sender root node sends probe query messages using the
Replication Segment defined in [I-D.spring-sr-p2mp-policy] for the
P2MP SR Policy as shown in Figure 7.
o Each responder leaf node adds the "Source Address" TLV (Type 130)
[RFC6374] with its IP address in the probe response messages.
This TLV allows the sender 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 of the P2MP SR Policy.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Replication SID | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GAL (value 13) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Reserved | GAL Channel Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: With Replication Segment for SR-MPLS Policy
8. ECMP for SR-MPLS 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 each of the ECMP path of an SR Policy.
Forwarding plane has various hashing functions available to forward
packets on specific ECMP paths. For SR-MPLS Policy, sweeping of
entropy label [RFC6790] values can be used in PM probe messages to
take advantage of the hashing function in forwarding plane to
influence the ECMP path taken by them.
The considerations for performance loss measurement for different
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ECMP paths of an SR Policy are outside the scope of this document.
9. SR Link Extended TE Metrics Advertisements
The extended TE metrics for SR link delay and loss computed using the
performance measurement procedures described in this document can be
advertised in the routing domain as follows:
o For OSPF, ISIS, and BGP-LS, protocol extensions defined in
[RFC7471], [RFC8570], and [RFC8571] are used, respectively for
advertising the extended TE link metrics in the network.
o The advertised delay-variance metric is computed as specified in
Section 4.2 of [RFC5481].
o The extended TE link one-way delay metrics can be computed using
two-way delay measurement or round-trip delay measurement from
loopback mode by dividing the measured delay values by 2.
o The extended TE link delay and loss metrics are advertised for
Layer 2 bundle members in OSPF [I-D.lsr-ospf-l2bundles] and ISIS
[I-D.isis-l2bundles] using the same mechanisms defined in
[RFC7471] and [RFC8570], respectively.
10. Security Considerations
This document describes the procedures for performance delay and loss
measurement for SR-MPLS networks, for both links and end-to-end SR
Policies using the mechanisms defined in [RFC6374] and [RFC7876].
This document does not introduce any additional security
considerations other than those covered in [RFC6374], [RFC7471],
[RFC8570], [RFC8571], and [RFC7876].
11. IANA Considerations
IANA is requested to allocate a value for the following optional
Return Path TLV Type for RFC 6374 to be carried in PM probe query
messages:
o Type TBA1: Return Path TLV
IANA is requested to allocate the values for the following Sub-TLV
Types for the Return Path TLV for RFC 6374.
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o Type (value 1): SR-MPLS Label Stack of the Reverse SR Path
o Type (value 2): SR-MPLS Binding SID [I-D.pce-binding-label-sid] of
the Reverse SR Policy
IANA is also requested to allocate a value for the following optional
Block Number TLV Type for RFC 6374 to be carried in the PM probe
query and response messages for loss measurement:
o Type TBA2: Block Number TLV
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay
Measurement for MPLS networks', RFC 6374, September 2011.
[RFC7876] Bryant, S., Sivabalan, S., and Soni, S., "UDP Return Path
for Packet Loss and Delay Measurement for MPLS Networks",
RFC 7876, July 2016.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", RFC 8174, May 2017.
12.2. Informative References
[IEEE1588] IEEE, "1588-2008 IEEE Standard for a Precision Clock
Synchronization Protocol for Networked Measurement and
Control Systems", March 2008.
[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.
[RFC5481] Morton, A. and B. Claise, "Packet Delay Variation
Applicability Statement", RFC 5481, March 2009.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
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L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, November 2012.
[RFC7679] Almes, G., et al., "A One-Way Delay Metric for IP
Performance Metrics (IPPM)', RFC 7679, January 2016.
[RFC7471] Giacalone, S., et al., "OSPF Traffic Engineering (TE)
Metric Extensions", RFC 7471, March 2015.
[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, July 2018.
[RFC8570] Ginsberg, L. Ed., et al., "IS-IS Traffic Engineering (TE)
Metric Extensions", RFC 8570, March 2019.
[RFC8571] Ginsberg, L. Ed., et al., "BGP - Link State (BGP-LS)
Advertisement of IGP Traffic Engineering Performance
Metric Extensions", RFC 8571, March 2019.
[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
Segment for Multi-point Service Delivery",
draft-voyer-spring-sr-replication-segment, work in
progress.
[I-D.pce-binding-label-sid] Filsfils, C., et al., "Carrying Binding
Label/Segment-ID in PCE-based Networks",
draft-ietf-pce-binding-label-sid, 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.
[I-D.mpls-ioam-sr] Gandhi, R. Ed., et al., "Segment Routing with
MPLS Data Plane Encapsulation for In-situ OAM Data",
draft-gandhi-mpls-ioam-sr, work in progress.
[I-D.lsr-ospf-l2bundles] Talaulikar, K., et al., "Advertising L2
Bundle Member Link Attributes in OSPF",
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draft-ketant-lsr-ospf-l2bundles, work in progress.
[I-D.isis-l2bundles] Ginsberg, L., et al., "Advertising L2 Bundle
Member Link Attributes in IS-IS",
draft-ietf-isis-l2bundles, work in progress.
[I-D.bidir-sr] Li, C., et al., "PCEP Extensions for Associated
Bidirectional Segment Routing (SR) Paths",
draft-li-pce-sr-bidir-path, work in progress.
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Acknowledgments
The authors would like to thank Thierry Couture for the discussions
on the use-cases for the performance measurement in segment routing
networks. The authors would like to thank Greg Mirsky for providing
many useful comments and suggestions. The authors would also like to
thank Stewart Bryant, Sam Aldrin, Tarek Saad, and Rajiv Asati for
their review comments.
Contributors
Sagar Soni
Cisco Systems, Inc.
Email: sagsoni@cisco.com
Patrick Khordoc
Cisco Systems, Inc.
Email: pkhordoc@cisco.com
Zafar Ali
Cisco Systems, Inc.
Email: zali@cisco.com
Pier Luigi Ventre
CNIT
Italy
Email: pierluigi.ventre@cnit.it
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
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Email: daniel.voyer@bell.ca
Stefano Salsano
Universita di Roma "Tor Vergata"
Italy
Email: stefano.salsano@uniroma2.it
Mach(Guoyi) Chen
Huawei
Email: mach.chen@huawei.com
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