MPLS Working Group R. Gandhi, Ed.
Internet-Draft C. Filsfils
Intended status: Standards Track Cisco Systems, Inc.
Expires: November 6, 2021 D. Voyer
Bell Canada
S. Salsano
Universita di Roma "Tor Vergata"
M. Chen
Huawei
May 05, 2021
Performance Measurement Using RFC 6374 for Segment Routing Networks with
MPLS Data Plane
draft-ietf-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. This
document utilizes these mechanisms for Performance Delay and Loss
Measurements in SR networks with MPLS data plane (SR-MPLS), for both
SR-MPLS links and end-to-end SR-MPLS paths including Policies. In
addition, this document defines Return Path TLV and Block Number TLV
extensions for RFC 6374.
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 November 6, 2021.
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Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
2.3. Reference Topology . . . . . . . . . . . . . . . . . . . 4
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Query and Response Message . . . . . . . . . . . . . . . . . 6
4.1. Query Message for SR-MPLS Links and Policies . . . . . . 6
4.1.1. Query Message for SR-MPLS Links . . . . . . . . . . . 6
4.1.2. Query Message for SR-MPLS Policies . . . . . . . . . 6
4.2. Response Message for SR-MPLS Links and Policies . . . . . 7
4.2.1. One-way Measurement Mode . . . . . . . . . . . . . . 7
4.2.2. Two-way Measurement Mode . . . . . . . . . . . . . . 8
4.2.3. Loopback Measurement Mode . . . . . . . . . . . . . . 8
5. Delay Measurement . . . . . . . . . . . . . . . . . . . . . . 8
5.1. Delay Measurement Message Format . . . . . . . . . . . . 8
5.2. Timestamps . . . . . . . . . . . . . . . . . . . . . . . 9
6. Loss Measurement . . . . . . . . . . . . . . . . . . . . . . 9
6.1. Loss Measurement Message Format . . . . . . . . . . . . . 9
6.2. Combined Loss/Delay Measurement Message Format . . . . . 9
6.3. Counters . . . . . . . . . . . . . . . . . . . . . . . . 10
7. TLV Extensions . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Return Path TLV Extension . . . . . . . . . . . . . . . . 10
7.1.1. Return Path Sub-TLV Extension . . . . . . . . . . . . 11
7.2. Block Number TLV Extension . . . . . . . . . . . . . . . 12
8. Performance Measurement for P2MP SR-MPLS Policies . . . . . . 13
9. ECMP for SR-MPLS Policies . . . . . . . . . . . . . . . . . . 14
10. SR-MPLS Link Extended TE Metrics Advertisements . . . . . . . 14
11. Backwards Compatibility . . . . . . . . . . . . . . . . . . . 15
12. Security Considerations . . . . . . . . . . . . . . . . . . . 15
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
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14. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
14.1. Normative References . . . . . . . . . . . . . . . . . . 16
14.2. Informative References . . . . . . . . . . . . . . . . . 17
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 19
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction
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
query and response messages. [RFC7876] specifies mechanisms for
sending and processing out-of-band responses over an UDP return path
when receiving RFC 6374 based query messages. These mechanisms are
also well-suited in SR-MPLS networks.
This document utilizes the mechanisms defined in [RFC6374] for
Performance Delay and Loss Measurements in SR-MPLS networks, for both
SR-MPLS links and end-to-end SR-MPLS paths including Policies. In
addition, this document defines Return Path TLV and Block Number TLV
extensions for [RFC6374].
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.
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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.
2.3. Reference Topology
In the reference topology shown in Figure 1, the querier node R1
initiates a query message and the responder node R3 sends a response
message for the query message received. The response message is sent
back to the querier node R1 in-band on the same path (same set of
links and nodes) or a different path in the reverse direction.
SR is enabled with MPLS data plane on nodes R1 and R3. The nodes R1
and R3 may be directly connected via a link enabled with MPLS
(Section 2.9.1 of [RFC6374]) or a Point-to-Point (P2P) SR-MPLS path
[RFC8402]. The link may be a physical interface, virtual link, or
Link Aggregation Group (LAG) [IEEE802.1AX], or Layer-2 LAG bundle
member link. The SR-MPLS path may be an SR-MPLS Policy
[I-D.ietf-spring-segment-routing-policy] on node R1 (called head-end)
with destination to node R3 (called tail-end).
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T1 T2
/ \
+-------+ Query +-------+
| | - - - - - - - - - ->| |
| R1 |=====================| R3 |
| |<- - - - - - - - - - | |
+-------+ Response +-------+
\ /
T4 T3
Querier Responder
Figure 1: Reference Topology
3. Overview
For delay and loss measurement in SR-MPLS networks, the procedures
defined in [RFC6374] are used in this document. Note that one-way,
two-way and round-trip delay measurements are defined in Section 2.4
of [RFC6374] and are further described in this document for SR-MPLS
networks. Similarly, packet loss measurements are defined in
Section 2.2 of [RFC6374] and are further described in this document
for SR-MPLS networks.
In SR-MPLS networks, the query and response messages defined in
[RFC6374] are sent as following:
o For delay measurement, the query messages are sent in-band (on the
same path as data traffic) for SR-MPLS links and end-to-end SR-
MPLS paths to collect transmit and receive timestamps.
o For loss measurement, the query messages are sent in-band (on the
same path as data traffic) for SR-MPLS links and end-to-end SR-
MPLS paths to collect transmit and receive traffic counters (e.g.
for traffic received on the incoming link for the link loss and
for the incoming Path Segment Identifier (PSID) for the end-to-end
SR-MPLS path loss).
It may be desired in SR-MPLS networks that the same path (same set of
links and nodes) between the querier and responder be used in both
directions of the measurement. This is achieved by using the SR-MPLS
Return Path TLV extension defined in this document.
The packet loss measurement using Alternate-Marking Method defined in
[RFC8321] requires collecting Block Number of the traffic counters.
This is achieved by using the Block Number TLV extension defined in
this document.
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The performance measurement procedure for SR-MPLS links can be used
to compute extended Traffic Engineering (TE) metrics for delay and
loss as described in this document. The metrics are advertised in
the network using the routing protocol extensions defined in
[RFC7471], [RFC8570], and [RFC8571].
The In-Situ Operations, Administration, and Maintenance (IOAM)
mechanisms for SR-MPLS defined in [I-D.gandhi-mpls-ioam-sr] are used
to record OAM information in the packets, and are outside the scope
of this document.
4. Query and Response Message
As described in Section 2.9.1 of [RFC6374], the query and response
messages flow over an MPLS Generic Associated Channel (G-ACh). These
query and response messages contain G-ACh Label (GAL) (value 13, with
S=1). The GAL is followed by an Associated Channel Header (ACH),
where Channel Type identifies the measurement 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GAL (value 13) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Reserved | Channel Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: RFC 6374 Query and Response Message Header
4.1. Query Message for SR-MPLS Links and Policies
4.1.1. Query Message for SR-MPLS Links
A query message as shown in Figure 2 is sent over the SR-MPLS links
for both delay and loss measurement using the procedures described in
[RFC6374]. For SR-MPLS links, the TTL value is set to 1 in the SR-
MPLS header.
4.1.2. Query Message for SR-MPLS Policies
A query message for an end-to-end SR-MPLS Policy, for both delay and
loss measurement, 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) 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 | Channel Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Example Query Message Header for an End-to-end SR-MPLS
Policy
The SR-MPLS label stack can be empty (format as shown in Figure 2) to
indicate Implicit NULL label case.
For SR-MPLS Policy performance measurement, in order to ensure that
the query message is processed by the intended responder, Destination
Address TLV (Type 129) [RFC6374] MAY be sent in the query message.
The responder only returns Success in Control Code if it is the
intended destination for the query. Otherwise, it MUST return 0x15:
Error - Invalid Destination Node Identifier [RFC6374].
4.2. Response Message for SR-MPLS Links and Policies
4.2.1. One-way Measurement Mode
In one-way measurement mode defined in Section 2.4 of [RFC6374], the
querier can receive "out-of-band" response messages with IP/UDP
header by properly setting the UDP Return Object (URO) TLV in the
query message. The URO TLV (Type=131) is defined in [RFC7876] and
includes the UDP-Destination-Port and IP Address. When the querier
sets an IP address and an UDP port in the URO TLV, the response is
sent to that IP address as destination address and UDP port as
destination port. In addition, the "control code" in the query
message is set to "out-of-band response requested".
In one-way delay measurement mode, as per Reference Topology, the
timestamps T1 and T2 are collected by the query and response
messages. Both these timestamps are used to measure one-way delay as
(T2 - T1).
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4.2.2. Two-way Measurement Mode
In two-way measurement mode defined in Section 2.4 of [RFC6374], the
response messages are sent back to the querier in-band on the same
link or the same end-to-end SR-MPLS path (same set of links and
nodes) in the reverse direction.
For SR-MPLS links, the response message (format as shown in Figure 2)
is sent back on the same incoming link where the query message is
received. In this case, the "control code" in the query message is
set to "in-band response requested".
For end-to-end SR-MPLS paths, the responder needs to transmit the
response message (example as shown in Figure 3) on a specific return
SR-MPLS path [I-D.ietf-pce-sr-bidir-path]. The querier can request
in the query message to the responder to send the response message
back on a given return path using the SR-MPLS Segment List sub-TLV in
the Return Path TLV defined in this document.
In two-way delay measurement mode, as per Reference Topology, all
timestamps T1, T2, T3, and T4 are collected by the query and response
messages. All four timestamps are used to measure two-way delay as
((T4 - T1) - (T3 - T2)).
4.2.3. 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 circular SR-
MPLS path [I-D.ietf-pce-sr-bidir-path]. The query messages in this
case also carry the return path label stack as part of the MPLS
header. The GAL is carried at the bottom of the label stack (with
S=1) (example as shown in Figure 3).
As the responder does not process the query messages and generate
response messages, the Loopback Request object (Type 3) [RFC6374] is
not required for an end-to-end SR-MPLS path.
In loopback delay measurement mode, as per Reference Topology, the
timestamps T1 and T4 are collected by the query messages. Both these
timestamps are used to measure round-trip delay as (T4 - T1).
5. Delay Measurement
5.1. Delay Measurement Message Format
As defined in [RFC6374], MPLS DM query and response messages use
Associated Channel Header (ACH) (value 0x000C for delay measurement)
[RFC6374], which identifies the message type, and the message payload
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following the ACH. For both SR-MPLS links and end-to-end 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 delay measurement, for both SR-MPLS links and end-to-end SR-MPLS
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]. The timestamping in hardware is recommended
in SR-MPLS networks.
6. 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.
6.1. Loss Measurement Message Format
As defined in [RFC6374], MPLS LM 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-MPLS links and end-to-end 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 loss measurement, for both SR-MPLS links and end-to-end SR-MPLS
Policies.
6.2. Combined Loss/Delay Measurement Message Format
As defined in [RFC6374], Combined DM+LM query and response messages
use Associated Channel Header (ACH) (value 0x000D for direct loss and
delay measurement or value 0x000E for inferred loss and delay
measurement), which identifies the message type, and the message
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payload following the ACH. For both SR-MPLS links and end-to-end SR-
MPLS Policies, the same MPLS DM+LM ACH value is used.
The message payload as defined in Section 3.3 of [RFC6374] is used
for combined delay and loss measurement, for both SR-MPLS links and
end-to-end SR-MPLS Policies.
6.3. Counters
The Path Segment Identifier (PSID)
[I-D.ietf-spring-mpls-path-segment] carried in the received data
packet for the traffic flow under measurement can be used for
accounting received traffic on the on the egress node of the SR-MPLS
Policy. In direct mode, the PSID in the received query message as
shown in Figure 4 can be used to associate the receive traffic
counter on the responder to detect the transmit packet loss for the
end-to-end SR-MPLS Policy.
In inferred mode, the PSID in the received query message as shown in
Figure 4 can be used to count the received query messages on the
responder to detect the transmit packet loss for an end-to-end SR-
MPLS 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 | Channel Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Example With Path Segment Identifier for SR-MPLS Policy
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
[I-D.ietf-spring-segment-routing-policy].
7. TLV Extensions
7.1. Return Path TLV Extension
In two-way measurement mode, the responder needs to send the response
message on a specific return path. The querier can request in the
query message to the responder to send a response message back on a
given return path (e.g. co-routed SR-MPLS path for two-way
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measurement). This way the responder avoids creating and maintaining
extra dynamic SR states for the return paths.
In one-way measurement mode, the querier can send its reachability
information to the responder using Return Path TLV.
[RFC6374] defines query and response messages those can include or
more optional TLVs. New TLV Type (TBA2) is defined in this document
for Return Path to carry return path information in query messages.
The format of the Return Path TLV is shown in 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 = TBA2 | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Return Path Sub-TLV |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Return Path TLV
The Return Path TLV is a Mandatory TLV Type. The querier MUST only
insert one Return Path TLV in the query message. The responder that
supports this TLV, MUST only process the first Return Path TLV and
ignore the other Return Path TLVs if present. The responder also
MUST NOT add Return Path TLV in the response message. The Reserved
field MUST be set to 0 and MUST be ignored on the receive side.
7.1.1. Return Path Sub-TLV Extension
The Return Path TLV contains a Sub-TLV to carry the return path. The
format of the SR-MPLS Segment List Sub-TLV is shown in Figure 6. The
SR-MPLS Segment List Sub-TLV contains SR-MPLS Label Stack. The Label
entries in the Segment List MUST be in network order. The SR-MPLS
Segment List Sub-TLV in the Return Path TLV is of the following Type:
o Type (value 1): SR-MPLS Segment List of the Return Path
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label(1) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label(n) (bottom of stack) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: SR-MPLS Segment List Sub-TLV in Return Path TLV
An SR-MPLS Segment List Sub-TLV may carry only Binding SID
[I-D.ietf-pce-binding-label-sid] of the Return SR-MPLS Policy.
The Return Path TLV MUST carry only one Return Path Sub-TLV. The
responder that supports this Sub-TLV, MUST only process the first
Return Path Sub-TLV and ignore the other Return Path Sub-TLVs if
present. The responder also MUST send response message back on the
return path specified in the Return Path Sub-TLV. The Reserved field
MUST be set to 0 and MUST be ignored on the receive side.
7.2. Block Number TLV Extension
The direct mode loss measurement using Alternate-Marking Method
defined in [RFC8321] requires collecting Block Number of the counters
for the data traffic flow under measurement. To be able to correlate
the transmit and receive traffic counters of the matching Block
Number, the Block Number of the traffic counters is carried in the LM
query and response messages.
[RFC6374] defines query and response messages those can include one
or more optional TLVs. New TLV Type (value TBA1) is defined in this
document to carry the Block Number (8-bit) of the traffic counters in
the LM query and response messages. The format of the Block Number
TLV is shown in Figure 7:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = TBA1 | Length | Reserved |R| Block Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Block Number TLV
The Block Number TLV is a Mandatory TLV Type. The querier MUST only
insert one Block Number TLV in the query message to identify the
Block Number for the traffic counters in the forward direction. The
responder that supports this TLV, MUST only inert one Block Number
TLV in the response message to identify the Block Number for the
traffic counters in the reverse direction. The responder also MUST
return the first Block Number TLV from the query message and ignore
the other Block Number TLVs if present. The R Flag MUST be clear in
the query message and set in the response message. The Reserved
field MUST be set to 0 and MUST be ignored on the receive side.
8. Performance Measurement for P2MP SR-MPLS Policies
The Point-to-Multipoint (P2MP) SR-MPLS path that originates from a
root node terminates on multiple destinations called leaf nodes (e.g.
P2MP SR-MPLS Policy [I-D.ietf-pim-sr-p2mp-policy]).
The procedures for delay and loss measurement described in this
document for end-to-end P2P SR-MPLS Policies are also equally
applicable to the P2MP SR-MPLS Policies. The procedure for one-way
measurement is defined as following:
o The querier root node sends query messages using the Tree-SID
defined in [I-D.ietf-pim-sr-p2mp-policy] for the P2MP SR-MPLS
Policy as shown in Figure 8. The query messages may contain the
replication SID as defined in
[I-D.ietf-spring-sr-replication-segment].
o Each responder leaf node sends its node address in the "Source
Address" TLV (Type 130) [RFC6374] in the response messages. This
TLV allows the querier root node to identify the responder leaf
nodes of the P2MP SR-MPLS Policy.
o The P2MP root node measures the delay and loss performance for
each P2MP leaf node individually.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tree-SID | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GAL (value 13) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Reserved | Channel Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Example Query with Tree-SID for SR-MPLS Policy
The considerations for two-way and loopback measurement modes for
P2MP SR-MPLS Policy (e.g. for co-routed bidirectional SR-MPLS path)
are outside the scope of this document.
9. ECMP for SR-MPLS Policies
An SR-MPLS 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-MPLS Policy can
result in ECMP paths via transit nodes part of that Anycast group.
The query and response messages need to be sent to traverse different
ECMP paths to measure delay of each of the ECMP path of an SR-MPLS
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 query and response
messages to take advantage of the hashing function in forwarding
plane to influence the ECMP path taken by them.
The considerations for loss measurement for different ECMP paths of
an SR-MPLS Policy are outside the scope of this document.
10. SR-MPLS Link Extended TE Metrics Advertisements
The extended TE metrics for SR-MPLS link delay and loss can be
computed using the performance measurement procedures described in
this document to advertise in the routing domain as follows:
o For OSPF, ISIS, and BGP-LS, protocol extensions defined in
[RFC7471], [RFC8570], and [RFC8571], respectively, are used for
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advertising the extended TE link delay and loss metrics in the
network.
o The extended TE link delay and loss metrics are advertised for
Layer-2 LAG bundle member links in OSPF
[I-D.ietf-lsr-ospf-l2bundles] and ISIS [RFC8668] using the same
protocol extensions defined in [RFC7471] and [RFC8570],
respectively.
o The advertised delay-variance metric, Packet Delay Variation (PDV)
is computed as described in Section 4.2 of [RFC5481].
o In the absence of one-way delay measurement, the extended TE link
one-way delay metrics can be computed using the two-way and round-
trip delay values by dividing the values by 2.
11. Backwards Compatibility
The procedures defined in this document are backwards compatible with
the procedures defined in [RFC6374] at both querier and responder.
If the responder does not support the new Mandatory TLV Types defined
in this document, it MUST return Error 0x17: Unsupported Mandatory
TLV Object as per [RFC6374].
12. Security Considerations
This document describes the procedures for performance delay and loss
measurement for SR-MPLS networks, for both SR-MPLS links and end-to-
end SR-MPLS 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].
13. IANA Considerations
IANA is requested to allocate a value for the following Mandatory
Block Number TLV Type for [RFC6374] to be carried in the query and
response messages from the "MPLS Loss/Delay Measurement TLV Object"
registry contained within the "Generic Associated Channel (G-ACh)
Parameters" registry set:
o Type TBA1: Block Number TLV
IANA is also requested to allocate a value for the following
Mandatory Return Path TLV Type for [RFC6374] to be carried in the
query messages from the "MPLS Loss/Delay Measurement TLV Object"
registry contained within the "Generic Associated Channel (G-ACh)
Parameters" registry set:
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o Type TBA2: Return Path TLV
IANA is requested to create the "Return Path Sub-TLV" sub-registry as
part of the Return Path TLV registry. All code points in the range 1
through 127 in this registry shall be allocated according to the
"IETF Review" procedure as specified in [RFC8126]. Code points in
the range 128 through 239 in this registry shall be allocated
according to the "First Come First Served" procedure as specified in
[RFC8126]. Remaining code points are allocated according to Table 1:
+-----------+--------------+---------------+
| Value | Description | Reference |
+-----------+--------------+---------------+
| 0 | Reserved | This document |
| 1 - 127 | Unassigned | This document |
| 128 - 239 | Unassigned | This document |
| 240 - 249 | Experimental | This document |
| 250 - 254 | Private Use | This document |
| 255 | Reserved | This document |
+-----------+--------------+---------------+
Table 1: Return Path Sub-TLV Type Sub-Registry
This document defines the following new values in the Return Path
Sub-TLV sub-registry:
+-------+-----------------------------------------+---------------+
| Value | Description | Reference |
+-------+-----------------------------------------+---------------+
| 1 | SR-MPLS Segment List of the Return Path | This document |
+-------+-----------------------------------------+---------------+
Table 2: Return Path Sub-TLV Types
14. References
14.1. 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>.
[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>.
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[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>.
14.2. Informative References
[IEEE1588]
IEEE, "1588-2008 IEEE Standard for a Precision Clock
Synchronization Protocol for Networked Measurement and
Control Systems", March 2008.
[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>.
[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>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[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>.
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[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., Talaulikar, K., Voyer, D., Bogdanov, A., and
P. Mattes, "Segment Routing Policy Architecture", draft-
ietf-spring-segment-routing-policy-09 (work in progress),
November 2020.
[I-D.ietf-pim-sr-p2mp-policy]
Voyer, D., Filsfils, C., Parekh, R., Bidgoli, H., and Z.
Zhang, "Segment Routing Point-to-Multipoint Policy",
draft-ietf-pim-sr-p2mp-policy-02 (work in progress),
February 2021.
[I-D.ietf-spring-sr-replication-segment]
Voyer, D., Filsfils, C., Parekh, R., Bidgoli, H., and Z.
Zhang, "SR Replication Segment for Multi-point Service
Delivery", draft-ietf-spring-sr-replication-segment-04
(work in progress), February 2021.
[I-D.ietf-pce-binding-label-sid]
Sivabalan, S., Filsfils, C., Tantsura, J., Previdi, S.,
and C. Li, "Carrying Binding Label/Segment Identifier in
PCE-based Networks.", draft-ietf-pce-binding-label-sid-08
(work in progress), April 2021.
[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-04 (work in progress),
April 2021.
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[I-D.ietf-lsr-ospf-l2bundles]
Talaulikar, K. and P. Psenak, "Advertising L2 Bundle
Member Link Attributes in OSPF", draft-ietf-lsr-ospf-
l2bundles-01 (work in progress), April 2021.
[I-D.ietf-pce-sr-bidir-path]
Li, C., Chen, M., Cheng, W., Gandhi, R., and Q. Xiong,
"Path Computation Element Communication Protocol (PCEP)
Extensions for Associated Bidirectional Segment Routing
(SR) Paths", draft-ietf-pce-sr-bidir-path-05 (work in
progress), January 2021.
[I-D.gandhi-mpls-ioam-sr]
Gandhi, R., Ali, Z., Filsfils, C., Brockners, F., Wen, B.,
and V. Kozak, "MPLS Data Plane Encapsulation for In-situ
OAM Data", draft-gandhi-mpls-ioam-sr-06 (work in
progress), February 2021.
[IEEE802.1AX]
IEEE Std. 802.1AX, "IEEE Standard for Local and
metropolitan area networks - Link Aggregation", November
2008.
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. Thanks to Huaimo Chen, Yimin Shen, and Xufeng Liu for
MPLS-RT expert review.
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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