MPLS Working Group R. Gandhi, Ed.
Internet-Draft C. Filsfils
Intended status: Standards Track Cisco Systems, Inc.
Expires: September 7, 2020 D. Voyer
Bell Canada
S. Salsano
Universita di Roma "Tor Vergata"
M. Chen
Huawei
March 6, 2020
Performance Measurement for Segment Routing Networks with MPLS Data
Plane
draft-gandhi-mpls-rfc6374-sr-02
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 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.
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 September 7, 2020.
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Copyright Notice
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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 Messages . . . . . . . . . . . . . . 6
4.1. Probe Message for SR-MPLS Links . . . . . . . . . . . . . 6
4.2. Probe Message for SR-MPLS Policies . . . . . . . . . . . 6
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 . . . . . . . . . . . . . . 8
4.3.3. Loopback Measurement Mode . . . . . . . . . . . . . . 8
4.4. Return Path TLV . . . . . . . . . . . . . . . . . . . . . 8
5. Performance Delay Measurement . . . . . . . . . . . . . . . . 10
5.1. Delay Measurement Message Format . . . . . . . . . . . . 10
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 . . . . . . . . 12
8. ECMP for SR-MPLS Policies . . . . . . . . . . . . . . . . . . 13
9. SR Link Extended TE Metrics Advertisements . . . . . . . . . 13
10. Security Considerations . . . . . . . . . . . . . . . . . . . 14
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
12.1. Normative References . . . . . . . . . . . . . . . . . . 14
12.2. Informative References . . . . . . . . . . . . . . . . . 15
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 17
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
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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.ietf-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 when using
MPLS data plane (SR-MPLS). [RFC6374] also supports "direct mode"
Loss Measurement (LM), which is 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.ietf-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.ietf-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.voyer-spring-sr-replication-segment].
+-------+ t1 Query t2 +-------+
| | - - - - - - - - - ->| |
| R1 |---------------------| R5 |
| |<- - - - - - - - - - | |
+-------+ t4 Response t3 +-------+
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 SR 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 SR 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
responder node does not have PM session state present).
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The In-Situ Operations, Administration, and Maintenance (IOAM)
mechanisms for SR-MPLS defined in [I-D.gandhi-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 Messages
4.1. Probe Message 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 message 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 2. The probe messages
are routed over the SR Links for both delay and loss measurement.
For SR-MPLS Links, the TTL value is set to 1 in the SR-MPLS header
for one-way and two-way measurement modes.
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 2: Probe Message Header for an SR-MPLS Link
4.2. Probe Message 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 message for an end-to-end measurement for SR Policy
contains SR-MPLS label stack
[I-D.ietf-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 3. For
SR-MPLS Policies, the TTL value is set to 255 in the SR-MPLS header.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 3: Probe Message Header for an End-to-end SR-MPLS Policy
The SR-MPLS label stack can be empty (as shown in Figure 2) to
indicate Implicit NULL label case.
For SR Policy performance measurement, in order to ensure that the
probe query message is processed by the intended responder node,
Destination Address TLV (Type 129) [RFC6374] can be sent in the probe
query message. The responder node only replies with Success in
Control Code if it is the intended destination for the probe query.
Otherwise, it MUST return 0x15: Error - Invalid Destination Node
Identifier.
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". In this delay measurement mode, as per Reference
Topology, timestamps t1 and t2 are collected by the probes. Only
timestamps t1 and t2 are used to measure one-way delay. The one-way
mode is applicable to both SR-MPLS Links and SR-MPLS Policies.
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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.ietf-pce-sr-bidir-path] 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". In this
delay measurement mode, as per Reference Topology, all timestamps t1,
t2, t3, and t4 are collected by the probes. All four timestamps are
used to measure two-way delay. The two-way mode is applicable to
both SR-MPLS Links and SR-MPLS Policies.
Specifically, the probe response message is sent back on the incoming
physical interface where the probe query message is received. This
is useful for example, in case of two-way measurement mode for Link
delay.
The Path Segment Identifier (PSID)
[I-D.ietf-spring-mpls-path-segment] of the forward SR-MPLS Policy in
the probe query can be used to find the associated reverse SR Policy
[I-D.ietf-pce-sr-bidir-path] to send the probe response message for
two-way measurement of SR-MPLS Policy unless when using the Return
Path TLV.
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.ietf-pce-sr-bidir-path]. 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. In this delay measurement mode, as per
Reference Topology, the timestamps t1 and t4 are collected by the
probes. Both these timestamps are used to measure round-trip delay.
The loopback mode for SR-MPLS Links is outside the scope of this
document.
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.
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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 4 and Figure 5:
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 4: 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label(1) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label(n) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: 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
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o Type (value 2): SR-MPLS Binding SID
[I-D.ietf-pce-binding-label-sid] of the Reverse SR Policy
The Return Path TLV is Mandatory when used. If responder does not
support this TLV, it MUST return Error 0x17: Unsupported Mandatory
TLV Object. 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.
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.
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], with hardware support in Segment Routing
networks.
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.
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For both of these modes of LM, Path Segment Identifier (PSID)
[I-D.ietf-spring-mpls-path-segment] is used for accounting received
traffic on the egress node of the SR-MPLS Policy as shown in
Figure 6. 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 6: With Path Segment Identifier for SR-MPLS Policy
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
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measurement. The format of the Block Number TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type TBA2 | Length | Reserved | Block Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Block Number TLV
The Block Number TLV is Mandatory when used. If responder does not
support this TLV, it MUST return Error 0x17: Unsupported Mandatory
TLV Object. 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
The procedures for delay and loss measurement described in this
document for Point-to-Point (P2P) SR-MPLS Policies
[I-D.ietf-spring-segment-routing-policy] are also equally applicable
to the Point-to-Multipoint (P2MP) SR-MPLS Policies as following:
o The sender root node sends probe query messages using the
Replication Segment defined in
[I-D.voyer-spring-sr-replication-segment] for the P2MP SR Policy
as shown in Figure 8.
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.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Replication SID | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GAL (value 13) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Reserved | GAL Channel Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Query 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
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 also be computed
using two-way delay measurement or round-trip delay measurement
from loopback mode by dividing the measured delay values by 2.
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o The extended TE link delay and loss metrics are advertised for
Layer 2 bundle members in OSPF [I-D.ketant-lsr-ospf-l2bundles] and
ISIS [RFC8668] 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 SR 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 mandatory
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.
o Type (value 1): SR-MPLS Label Stack of the Reverse SR Path
o Type (value 2): SR-MPLS Binding SID
[I-D.ietf-pce-binding-label-sid] of the Reverse SR Policy
IANA is also requested to allocate a value for the following
mandatory 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", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
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Internet-Draft RFC 6374 for SR-MPLS March 2020
[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay
Measurement for MPLS Networks", RFC 6374,
DOI 10.17487/RFC6374, September 2011,
<https://www.rfc-editor.org/info/rfc6374>.
[RFC7876] Bryant, S., Sivabalan, S., and S. Soni, "UDP Return Path
for Packet Loss and Delay Measurement for MPLS Networks",
RFC 7876, DOI 10.17487/RFC7876, July 2016,
<https://www.rfc-editor.org/info/rfc7876>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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, DOI 10.17487/RFC4656, September 2006,
<https://www.rfc-editor.org/info/rfc4656>.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, DOI 10.17487/RFC5357, October 2008,
<https://www.rfc-editor.org/info/rfc5357>.
[RFC5481] Morton, A. and B. Claise, "Packet Delay Variation
Applicability Statement", RFC 5481, DOI 10.17487/RFC5481,
March 2009, <https://www.rfc-editor.org/info/rfc5481>.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, DOI 10.17487/RFC6790, November 2012,
<https://www.rfc-editor.org/info/rfc6790>.
[RFC7679] Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton,
Ed., "A One-Way Delay Metric for IP Performance Metrics
(IPPM)", STD 81, RFC 7679, DOI 10.17487/RFC7679, January
2016, <https://www.rfc-editor.org/info/rfc7679>.
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[RFC7471] Giacalone, S., Ward, D., Drake, J., Atlas, A., and S.
Previdi, "OSPF Traffic Engineering (TE) Metric
Extensions", RFC 7471, DOI 10.17487/RFC7471, March 2015,
<https://www.rfc-editor.org/info/rfc7471>.
[RFC8321] Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli,
L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi,
"Alternate-Marking Method for Passive and Hybrid
Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321,
January 2018, <https://www.rfc-editor.org/info/rfc8321>.
[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>.
[RFC8570] Ginsberg, L., Ed., Previdi, S., Ed., Giacalone, S., Ward,
D., Drake, J., and Q. Wu, "IS-IS Traffic Engineering (TE)
Metric Extensions", RFC 8570, DOI 10.17487/RFC8570, March
2019, <https://www.rfc-editor.org/info/rfc8570>.
[RFC8571] Ginsberg, L., Ed., Previdi, S., Wu, Q., Tantsura, J., and
C. Filsfils, "BGP - Link State (BGP-LS) Advertisement of
IGP Traffic Engineering Performance Metric Extensions",
RFC 8571, DOI 10.17487/RFC8571, March 2019,
<https://www.rfc-editor.org/info/rfc8571>.
[RFC8668] Ginsberg, L., Ed., Bashandy, A., Filsfils, C., Nanduri,
M., and E. Aries, "Advertising Layer 2 Bundle Member Link
Attributes in IS-IS", RFC 8668, DOI 10.17487/RFC8668,
December 2019, <https://www.rfc-editor.org/info/rfc8668>.
[I-D.ietf-spring-segment-routing-policy]
Filsfils, C., Sivabalan, S., Voyer, D., Bogdanov, A., and
P. Mattes, "Segment Routing Policy Architecture", draft-
ietf-spring-segment-routing-policy-06 (work in progress),
December 2019.
[I-D.voyer-spring-sr-replication-segment]
Voyer, D., Filsfils, C., Parekh, R., Bidgoli, H., and Z.
Zhang, "SR Replication Segment for Multi-point Service
Delivery", draft-voyer-spring-sr-replication-segment-02
(work in progress), November 2019.
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[I-D.ietf-pce-binding-label-sid]
Sivabalan, S., Filsfils, C., Tantsura, J., Hardwick, J.,
Previdi, S., and C. Li, "Carrying Binding Label/Segment-ID
in PCE-based Networks.", draft-ietf-pce-binding-label-
sid-01 (work in progress), November 2019.
[I-D.ietf-spring-mpls-path-segment]
Cheng, W., Li, H., Chen, M., Gandhi, R., and R. Zigler,
"Path Segment in MPLS Based Segment Routing Network",
draft-ietf-spring-mpls-path-segment-02 (work in progress),
February 2020.
[I-D.gandhi-mpls-ioam-sr]
Gandhi, R., Ali, Z., Filsfils, C., Brockners, F., Wen, B.,
and V. Kozak, "Segment Routing with MPLS Data Plane
Encapsulation for In-situ OAM Data", draft-gandhi-mpls-
ioam-sr-01 (work in progress), December 2019.
[I-D.ketant-lsr-ospf-l2bundles]
Talaulikar, K. and P. Psenak, "Advertising L2 Bundle
Member Link Attributes in OSPF", draft-ketant-lsr-ospf-
l2bundles-01 (work in progress), January 2020.
[I-D.ietf-pce-sr-bidir-path]
Li, C., Chen, M., Cheng, W., Gandhi, R., and Q. Xiong,
"PCEP Extensions for Associated Bidirectional Segment
Routing (SR) Paths", draft-ietf-pce-sr-bidir-path-01 (work
in progress), February 2020.
Acknowledgments
The authors would like to thank Thierry Couture for the discussions
on the use-cases for the performance measurement in segment routing
networks. Authors would like to thank Patrick Khordoc for
implementing the mechanisms defined in this document. 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
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Sagar Soni
Cisco Systems, Inc.
Email: sagsoni@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
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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