Internet DRAFT - draft-ietf-mpls-rfc6374-sr
draft-ietf-mpls-rfc6374-sr
MPLS Working Group R. Gandhi, Ed.
Internet-Draft C. Filsfils
Intended status: Standards Track Cisco Systems, Inc.
Expires: 12 August 2024 D. Voyer
Bell Canada
S. Salsano
Universita di Roma "Tor Vergata"
M. Chen
Huawei
9 February 2024
Performance Measurement for Segment Routing Networks with MPLS Data
Plane
draft-ietf-mpls-rfc6374-sr-09
Abstract
Segment Routing (SR) leverages the source routing paradigm. SR is
applicable to Multiprotocol Label Switching data plane (SR-MPLS) as
specified in RFC 8402. RFC 6374 and RFC 7876 specify protocol
mechanisms to enable 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. RFC 9341 defines Alternate-Marking
Method using Block Number (BN) for data correlation mechanism for
packet loss measurement. This document utilizes these mechanisms for
Performance Delay and Loss Measurements in SR-MPLS networks, for both
links and end-to-end SR-MPLS paths including Policies.
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
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 12 August 2024.
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Copyright Notice
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
2.3. Reference Topology . . . . . . . . . . . . . . . . . . . 4
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Query and Response Messages . . . . . . . . . . . . . . . . . 6
4.1. Query Message for Links and Policies . . . . . . . . . . 6
4.1.1. Query Message for Links . . . . . . . . . . . . . . . 6
4.1.2. Query Message for SR-MPLS Policies . . . . . . . . . 6
4.2. Response Message for Links and Policies . . . . . . . . . 7
4.2.1. One-way Measurement Mode . . . . . . . . . . . . . . 7
4.2.2. Two-way Measurement Mode . . . . . . . . . . . . . . 7
4.2.3. Loopback Measurement Mode . . . . . . . . . . . . . . 8
5. Delay Measurement . . . . . . . . . . . . . . . . . . . . . . 8
5.1. Delay Measurement Message Format . . . . . . . . . . . . 8
6. Loss Measurement . . . . . . . . . . . . . . . . . . . . . . 8
6.1. Loss Measurement Message Format . . . . . . . . . . . . . 9
6.2. Combined Loss/Delay Measurement Message Format . . . . . 9
6.3. Counters . . . . . . . . . . . . . . . . . . . . . . . . 9
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. ECMP for SR-MPLS Policies . . . . . . . . . . . . . . . . . . 12
9. Extended TE Link Metrics Advertisements . . . . . . . . . . . 13
10. Backwards Compatibility . . . . . . . . . . . . . . . . . . . 13
11. Security Considerations . . . . . . . . . . . . . . . . . . . 13
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
13.1. Normative References . . . . . . . . . . . . . . . . . . 15
13.2. Informative References . . . . . . . . . . . . . . . . . 16
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Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 18
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction
Segment Routing (SR) leverages the source routing paradigm for
Software Defined Networks (SDNs). SR is applicable to both
Multiprotocol Label Switching (SR-MPLS) and IPv6 (SRv6) data planes
[RFC8402]. 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 [RFC9256]
are used to steer traffic through a specific, user-defined paths
using a list of Segments. A comprehensive SR Performance Measurement
toolset is one of the essential requirements to measure network
performance 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 query messages defined in [RFC6374]. These mechanisms
are also well-suited in SR-MPLS networks.
[RFC9341] defines Alternate-Marking Method using Block Number (BN)
for data correlation for packet loss measurement.
This document utilizes the mechanisms defined in [RFC6374], [RFC7876]
and [RFC9341] for Performance Delay and Loss Measurements in SR-MPLS
networks, for both links and end-to-end SR-MPLS paths including
Policies.
2. Conventions Used in This Document
2.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [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.
PSID: Path Segment Identifier.
SID: Segment Identifier.
SL: Segment List.
SR: Segment Routing.
SR-MPLS: Segment Routing with MPLS data plane.
TC: Traffic Class.
TE: Traffic Engineering.
TTL: Time-To-Live.
URO: UDP Return Object.
2.3. Reference Topology
In the Reference Topology shown in Figure 1, the querier node Q1
initiates a query message and the responder node R1 transmits a
response message for the query message received. The response
message may be sent back to the querier node Q1 on the same path
(same set of links and nodes) or a different path in the reverse
direction from the path taken towards the responder R1.
The T1 is a transmit timestamp and T4 is a receive timestamp, both
added by node Q1. The T2 is a receive timestamp and T3 is a transmit
timestamp, both added by node R1.
SR is enabled with MPLS data plane on nodes Q1 and R1. The nodes Q1
and R1 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 LAG member link. The
SR-MPLS path may be an SR-MPLS Policy [RFC9256] on node Q1 (called
head-end) with destination to node R1 (called tail-end).
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T1 T2
/ \
+-------+ Query +-------+
| | - - - - - - - - - ->| |
| Q1 |=====================| R1 |
| |<- - - - - - - - - - | |
+-------+ 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], [RFC7876] and [RFC9341] are used in this
document. Note that the 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, the
packet loss measurement is defined in Section 2.2 of [RFC6374] and is
further described in this document for SR-MPLS networks.
The packet loss measurement using Alternate-Marking Method defined in
[RFC9341] MAY use Block Number (BN) for data correlation. This is
achieved by using the Block Number TLV extension defined in this
document for MPLS networks.
In SR-MPLS networks, the query and response messages defined in
[RFC6374] are sent as following:
* For delay measurement, the query messages MUST be sent on the same
path as data traffic for links and end-to-end SR-MPLS paths to
collect transmit and receive timestamps.
* For loss measurement, the query messages MUST be sent on the same
path as data traffic for 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 packet loss and for the
incoming Path Segment Identifier (PSID)
[I-D.ietf-spring-mpls-path-segment] for the end-to-end SR-MPLS
path packet loss).
If it is 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, it is achieved by using the SR-MPLS
Return Path TLV extension defined in this document.
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The performance measurement procedure for 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].
4. Query and Response Messages
4.1. Query Message for Links and Policies
4.1.1. Query Message for Links
The query message as defined in [RFC6374] is sent over the links for
both delay and loss measurement. For links, the TTL value MUST be
set to 255 in the SR-MPLS header.
4.1.2. Query Message for SR-MPLS Policies
An SR-MPLS Policy Candidate-Path may contain a number of Segment
Lists (SLs) (i.e., stack of MPLS labels) [RFC9256]. The query
messages MUST be transmitted using each SL of the SR-MPLS Policy
Candidate-Path. A query message for an end-to-end SR-MPLS Policy,
used for delay and/or loss measurement, contains SR-MPLS label stack
of the Segment List(s) of the Candidate-Path, with the G-ACh Label
(GAL) at the bottom of the stack (with S=1) as shown in Figure 2.
For SR-MPLS, the TTL value MUST be set to 255 in the SR-MPLS header.
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 |1| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Reserved | Channel Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Example Query Message Header for an End-to-end SR-MPLS
Policy
The SR-MPLS label stack can be empty in the case of one hop SR-MPLS
Policy with Implicit NULL label.
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For an SR-MPLS Policy, to ensure that the query message is processed
by the intended responder, Destination Address TLV (Type 129)
[RFC6374] containing the address of the responder can be sent in the
query messages. The responder that supports this TLV MUST return
Success in "Control Code" [RFC6374] 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 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
message MUST be sent to that IP address as the destination address
and UDP port as the destination port. In addition, the "Control
Code" in the query message MUST be set to "out-of-band response
requested" [RFC6374].
4.2.2. Two-way Measurement Mode
In two-way measurement mode defined in Section 2.4 of [RFC6374], the
response messages are preferred to be sent back 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 to the querier.
For links, the response message as defined in [RFC6374] is sent back
on the same incoming link where the query message is received. In
this case, the "Control Code" in the query message MUST be set to
"in-band response requested" [RFC6374].
For end-to-end SR-MPLS paths, the responder transmits the response
message (example as shown in Figure 2) 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.
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4.2.3. Loopback Measurement Mode
The Loopback measurement mode defined in Section 2.8 of [RFC6374] is
used to measure round-trip delay for a bidirectional circular SR-MPLS
path [I-D.ietf-pce-sr-bidir-path]. In this mode, the received query
messages MUST NOT be punted out of the fast path in forwarding (i.e.,
to slow path or control- plane) at the responder. In other words,
the responder does not process the payload and generate response
messages. The loopback function simply returns the received query
message to the querier without responder modifications [RFC6374].
The loopback mode is done by generating "queries" with the Response
flag set to 1 and adding the Loopback Request object (Type 3)
[RFC6374]. The label stack in query messages in this case carry both
the forward and reverse paths in the MPLS header. The GAL is still
carried at the bottom of the label stack (with S=1) (example as shown
in Figure 2).
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
as defined in Section 3.2 [RFC6374] following the ACH. For both
links and end-to-end SR-MPLS Policies, the same MPLS DM ACH value
MUST be used.
6. Loss Measurement
The LM protocol can perform two distinct kinds of loss measurement as
described in Section 2.9.8 of [RFC6374].
* In inferred mode, LM will measure the loss of specially generated
test messages to infer the approximate data plane loss level.
Inferred mode LM provides only approximate loss accounting.
* 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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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 defined in
Section 3.1 [RFC6374] following the ACH. For both links and end-to-
end SR-MPLS Policies, the same MPLS LM ACH value MUST be used.
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
payload defined in Section 3.3 [RFC6374] following the ACH. For both
links and end-to-end SR-MPLS Policies, the same MPLS DM+LM ACH value
MUST be used.
6.3. Counters
The PSID [I-D.ietf-spring-mpls-path-segment] is carried in the
received data packet for the traffic flow under measurement for
accounting received traffic on the egress node of the SR-MPLS Policy.
In direct mode, the PSID in the received query message as shown in
Figure 3 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 messages as shown in
Figure 3 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 |1| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Reserved | Channel Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Example with Path Segment Identifier for SR-MPLS Policy
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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-MPLS
Policy [RFC9256].
7. TLV Extensions
7.1. Return Path TLV Extension
In two-way measurement mode, the responder may transmit the response
message on a specific return path, for example, in an ECMP
environment. 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 bidirectional path). This allows the
responder to avoid creating and maintaining additional states
(containing return paths) for the sessions.
The querier may not be directly reachable from the responder in a
network. The querier in this case MUST send its reachability path
information to the responder using the Return Path TLV.
[RFC6374] defines query and response messages those can include or
more optional TLVs. New TLV Type (TBA1) is defined in this document
for Return Path TLV to carry return path information in query
messages. The format of the Return Path TLV is shown in Figure 4:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = TBA1 | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Return Path Sub-TLV |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Return Path TLV
The Length is a one-byte field and is equal to the length of the
Return Path Sub-TLV and the Reserved field in bytes. Length MUST NOT
be 0.
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 that
supports this TLV, also MUST send response message back on the return
path specified in the Return Path TLV. 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.
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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 5. 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:
* Type (value 1): SR-MPLS Segment List of the Return Path
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=1 | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label(1) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label(n) | TC |1| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: SR-MPLS Segment List Sub-TLV in Return Path TLV
The SR-MPLS Label Stack contains a list of 32-bit Label Stack Entry
(LSE) that includes a 20-bit label value, 8-bit TTL value, 3-bit TC
value and 1-bit EOS (S) field. An SR-MPLS Segment List Sub-TLV may
carry only Binding SID label [I-D.ietf-pce-binding-label-sid] of the
Return SR-MPLS Policy.
The Length is a one-byte field and is equal to the length of the
label stack field and the Reserved field in bytes. Length MUST NOT
be 0.
The Return Path TLV MUST carry only one Return Path Sub-TLV and
Segment List in Return Path Sub-TLV MUST contain at least one
Segment. 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 that supports this Sub-TLV, 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.
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7.2. Block Number TLV Extension
The packet loss measurement using Alternate-Marking Method defined in
[RFC9341] MAY use Block Number (BN) for data correlation 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 TBA2) 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 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 |R| Block Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Block Number TLV
The Length is a one-byte field and is equal to 2 bytes.
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. 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 SHOULD be sent to traverse different
ECMP paths to measure delay of each of the ECMP path of a Segment
List of an SR-MPLS Policy Candidate-Path.
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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.
9. Extended TE Link Metrics Advertisements
The extended TE metrics for link delay and loss can be computed using
the performance measurement procedures described in this document and
advertised in the routing domain as follows:
* For OSPF, ISIS, and BGP-LS, protocol extensions defined in
[RFC7471], [RFC8570], and [RFC8571], respectively, are used for
advertising the extended TE link delay and loss metrics in the
network.
* The extended TE link delay and loss metrics are advertised for
Layer-2 LAG bundle member links in OSPF [RFC9356] and ISIS
[RFC8668] using the same protocol extensions defined in [RFC7471]
and [RFC8570], respectively.
* The advertised delay-variance metric, Packet Delay Variation (PDV)
is computed as described in Section 4.2 of [RFC5481].
10. 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].
11. Security Considerations
The security considerations specified in [RFC6374], [RFC7471],
[RFC8570], [RFC8571], [RFC7876], and [RFC9341] also apply to the
procedures described in this document.
The procedure defined in this document is intended for deployment in
a single operator administrative domain. As such, querier node,
responder node, forward and return paths are provisioned by the
operator for the probe session. It is assumed that the operator has
verified the integrity of the forward and return paths of the probe
packets.
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The "Return Path" TLV extensions defined in this document may be used
for potential address spoofing. For example, a query message may
carry a return path that has destination not local at the querier.
To prevent such possible attacks, the responder MAY drop the query
messages when it cannot determine whether the return path has the
destination local at the querier. The querier may send a proper
source address in the "Source Address" TLV that responder can use to
make that determination, for example, by checking the access control
list provisioned by the operator.
12. IANA Considerations
IANA is requested to allocate values for the following Mandatory TLV
Types for [RFC6374] from the "MPLS Loss/Delay Measurement TLV Object"
registry contained within the "Generic Associated Channel (G-ACh)
Parameters" registry set:
+=======+==================+===============+
| Value | Description | Reference |
+=======+==================+===============+
| TBA1 | Return Path TLV | This document |
+-------+------------------+---------------+
| TBA2 | Block Number TLV | This document |
+-------+------------------+---------------+
Table 1: MPLS Loss/Delay Measurement TLV
Types
The Block Number TLV is carried in the query and response messages
and Return Path TLV is carried in the query messages.
IANA is requested to create a sub-registry for "Return Path Sub-TLV
Type". All code points in the range 0 through 175 in this registry
shall be allocated according to the "IETF Review" procedure as
specified in [RFC8126]. Code points in the range 176 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 2:
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+===========+=========================+===============+
| Value | Description | Reference |
+===========+=========================+===============+
| 0 - 175 | IETF Review | This document |
+-----------+-------------------------+---------------+
| 176 - 239 | First Come First Served | This document |
+-----------+-------------------------+---------------+
| 240 - 251 | Experimental Use | This document |
+-----------+-------------------------+---------------+
| 252 - 255 | Private Use | This document |
+-----------+-------------------------+---------------+
Table 2: Return Path Sub-TLV Type Registry
This document defines the following values in the Return Path Sub-TLV
Type sub-registry:
+=======+=========================================+===============+
| Value | Description | Reference |
+=======+=========================================+===============+
| 0 | Reserved | This document |
+-------+-----------------------------------------+---------------+
| 1 | SR-MPLS Segment List of the Return Path | This document |
+-------+-----------------------------------------+---------------+
| 255 | Reserved | This document |
+-------+-----------------------------------------+---------------+
Table 3: Return Path Sub-TLV Types
13. References
13.1. 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>.
[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>.
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[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>.
13.2. Informative References
[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>.
[RFC9341] Fioccola, G., Ed., Cociglio, M., Mirsky, G., and T.
Mizrahi, "Alternate-Marking Method", RFC 9341,
DOI 10.17487/RFC9341, December 2022,
<https://www.rfc-editor.org/info/rfc9341>.
[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>.
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[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>.
[RFC9256] Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
P. Mattes, "Segment Routing Policy Architecture",
RFC 9256, July 2022,
<https://www.rfc-editor.org/info/rfc9256>.
[I-D.ietf-pce-binding-label-sid]
Sivabalan, S., Filsfils, C., Tantsura, J., Previdi, S.,
and C. L. (editor), "Carrying Binding Label/Segment
Identifier (SID) in PCE-based Networks.", Work in
Progress, Internet-Draft, draft-ietf-pce-binding-label-
sid-16, 27 March 2023, <https://www.ietf.org/archive/id/
draft-ietf-pce-binding-label-sid-16.txt>.
[I-D.ietf-spring-mpls-path-segment]
Cheng, W., Li, H., Li, C., Ed., Gandhi, R., and R. Zigler,
"Path Segment in MPLS Based Segment Routing Network", Work
in Progress, Internet-Draft, draft-ietf-spring-mpls-path-
segment-22, 30 November 2024,
<https://www.ietf.org/archive/id/draft-ietf-spring-mpls-
path-segment-22.txt>.
[RFC9356] Talaulikar, K. and P. Psenak, "Advertising L2 Bundle
Member Link Attributes in OSPF", RFC 9356, January 2023,
<https://www.rfc-editor.org/info/rfc9356>.
[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", Work in Progress, Internet-Draft, draft-ietf-
pce-sr-bidir-path-12, 9 September 2023,
<https://www.ietf.org/archive/id/draft-ietf-pce-sr-bidir-
path-12.txt>.
[IEEE802.1AX]
IEEE Std. 802.1AX, "IEEE Standard for Local and
metropolitan area networks - Link Aggregation", November
2008.
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Acknowledgments
The authors would like to thank Thierry Couture and Ianik Semco for
the discussions on the use-cases for the performance measurement in
segment routing networks. Authors would like to thank Patrick
Khordoc, Ruby Lin and Haowei Shi 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 and
Zhaohui Zhang for RTGDIR early review.
Contributors
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
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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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