Internet DRAFT - draft-gandhi-mpls-rfc6374-sr
draft-gandhi-mpls-rfc6374-sr
MPLS Working Group R. Gandhi, Ed.
Internet-Draft C. Filsfils
Intended status: Standards Track Cisco Systems, Inc.
Expires: December 27, 2020 D. Voyer
Bell Canada
S. Salsano
Universita di Roma "Tor Vergata"
M. Chen
Huawei
June 25, 2020
Performance Measurement Using RFC 6374 for Segment Routing Networks with
MPLS Data Plane
draft-gandhi-mpls-rfc6374-sr-05
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-MPLS Links and end-to-end Paths
including SR-MPLS 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 December 27, 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 Extensions . . . . . . . . . . . . . . . 8
5. Delay Measurement . . . . . . . . . . . . . . . . . . . . . . 10
5.1. Delay Measurement Message Format . . . . . . . . . . . . 10
5.2. Timestamps . . . . . . . . . . . . . . . . . . . . . . . 10
6. Loss Measurement . . . . . . . . . . . . . . . . . . . . . . 10
6.1. Loss Measurement Message Format . . . . . . . . . . . . . 11
6.2. Block Number TLV Extensions . . . . . . . . . . . . . . . 11
6.3. Combined Loss/Delay Measurement Message Format . . . . . 12
7. Performance Measurement for P2MP SR-MPLS Policies . . . . . . 12
8. ECMP for SR-MPLS Policies . . . . . . . . . . . . . . . . . . 13
9. SR-MPLS Link Extended TE Metrics Advertisements . . . . . . . 14
10. Backwards Compatibility . . . . . . . . . . . . . . . . . . . 14
11. Security Considerations . . . . . . . . . . . . . . . . . . . 14
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
13.1. Normative References . . . . . . . . . . . . . . . . . . 16
13.2. Informative References . . . . . . . . . . . . . . . . . 16
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 19
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Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
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 responses over
an UDP return path when receiving RFC 6374 based probe queries.
These procedures can be used to send out-of-band probe responses for
both SR-MPLS Links and Policies 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-MPLS Links and end-to-end Paths
including SR-MPLS 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-
MPLS Links are used to compute extended Traffic Engineering (TE)
metrics for delay and loss and can be advertised in the network using
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the routing protocol extensions defined in [RFC7471], [RFC8570], and
[RFC8571].
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.
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URO: UDP Return Object.
2.3. Reference Topology
In the reference topology shown in Figure 1, the querier node R1
initiates a performance measurement probe query and the responder
node R5 sends a probe response message for the query message
received. The probe response message is typically sent back to the
querier node R1.
SR is enabled with MPLS data plane on nodes R1 and R5. The nodes R1
and R5 may be directly connected via a Link enabled with MPLS or
there exists a Point-to-Point (P2P) SR-MPLS Path e.g. Policy
[I-D.ietf-spring-segment-routing-policy] on node R1 (called head-end)
with destination to node R5 (called tail-end).
t1 t2
/ \
+-------+ Query +-------+
| | - - - - - - - - - ->| |
| R1 |=====================| R5 |
| |<- - - - - - - - - - | |
+-------+ Response +-------+
\ /
t4 t3
Querier Responder
Figure 1: Reference Topology
3. Overview
For one-way, two-way and round-trip delay measurements, the
procedures defined in Section 2.4 and Section 2.6 of [RFC6374] are
used. For transmit and receive packet loss measurements, the
procedures defined in Section 2.2 and Section 2.6 of [RFC6374] are
used. For both SR-MPLS Links and end-to-end 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 querier node, and are
used to measure the delay experienced by the actual data traffic
flowing on the SR-MPLS Links and Policies.
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o For loss measurement, the probe messages are sent on the congruent
path of the data traffic by the querier node, and are used to
collect the receive traffic counters for the incoming link or
incoming SID where the probe query messages are received at the
responder node (incoming link or incoming SID needed since the
responder node does not have PM session state present).
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], 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
Links for both delay and loss measurement using the same procedure
described in [RFC6374]. 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], probe query and response
messages flow over the MPLS Generic Associated Channel (G-ACh). A
probe message for an end-to-end SR-MPLS Policy 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). 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: Example 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-MPLS 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] MAY be sent in the probe
query message. The responder node only returns Success in Control
Code if it is the intended destination for the probe query.
Otherwise, it MUST return 0x15: Error - Invalid Destination Node
Identifier [RFC6374].
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 querier node
can receive "out-of-band" probe responses 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 querier node sets its own
IP address in the URO TLV, the probe response is sent back by the
responder node to the querier 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 to measure
one-way delay. The one-way mode is applicable to both SR-MPLS Links
and Policies.
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4.3.2. Two-way Measurement Mode
In two-way performance measurement mode [RFC6374], when using a
bidirectional SR path [I-D.ietf-pce-sr-bidir-path], the probe
response message is sent back to the querier node on the congruent
path of the data traffic on the reverse direction SR-MPLS Link or
associated SR-MPLS 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
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-MPLS
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-MPLS Path
[I-D.ietf-pce-sr-bidir-path]. The probe query messages in this case
carries the reverse 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 probe messages and generate
response messages, and hence Loopback Request object (Type 3) is not
required for SR. 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.
4.4. Return Path TLV Extensions
For two-way performance measurement, the responder node needs to send
the probe response message on a specific reverse path. The querier
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-MPLS Policy state.
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For one-way performance measurement, the querier node address may not
be reachable via IP route from the responder node. The querier 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 information in the
probe query messages (in the payload). 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 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 a Mandatory TLV Type. The querier node MUST
only insert one Return Path TLV in the probe query message and the
responder node MUST only process the first Return Path TLV in the
probe query message and ignore other Return Path TLVs if present.
The responder node MUST send probe response message back on the
reverse path specified in the Return Path TLV and MUST NOT add Return
Path TLV in the probe response message.
5. 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-MPLS Links and end-
to-end Policies measurements, 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-MPLS Links and end-to-end
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. 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: Example 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-MPLS Links and end-to-end Policies measurements,
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-MPLS Links and end-to-end
Policies.
6.2. Block Number TLV Extensions
The loss measurement using Alternate-Marking method defined in
[RFC8321] requires to color the data traffic. To be able to
correlate 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. The
probe query and response messages currently specified in [RFC6374]
for loss measurement do not identify the Block Number of the
counters. The Block Number can also be used to aggregate performance
metrics collected.
[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
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counters in the probe query and response messages for loss
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 a Mandatory TLV Type. The querier 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.
6.3. Combined Loss/Delay Measurement Message Format
As defined in [RFC6374], Combined DM+LM probe 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 following the ACH. For both SR-MPLS Links and end-
to-end Policies measurements, the same MPLS ACH value is used.
The message payload as defined in Section 3.3 of [RFC6374] is used
for SR-MPLS combined delay and loss measurement, for both SR-MPLS
Links and end-to-end Policies.
7. 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.voyer-pim-sr-p2mp-policy] or P2MP Transport
[I-D.shen-spring-p2mp-transport-chain]).
The procedures for delay and loss measurement described in this
document for 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 probe query messages using the Tree-
SID defined in [I-D.voyer-pim-sr-p2mp-policy] for the P2MP SR-MPLS
Policy as shown in Figure 8.
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o The probe query messages can contain the replication SID as
defined in [I-D.voyer-spring-sr-replication-segment].
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 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 of the end-to-end P2MP 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tree-SID | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GAL (value 13) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Reserved | GAL Channel Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Example Probe Query with Tree-SID for SR-MPLS Policy
The probe query messages can also be sent using the scheme defined
for P2MP Transport using Chain Replication that may contain Bud SID
as defined in [I-D.shen-spring-p2mp-transport-chain].
The considerations for two-way mode for performance measurement for
P2MP SR-MPLS Policy (e.g. for bidirectional SR-MPLS Path) are outside
the scope of this document.
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 probe messages need to be sent to traverse different ECMP paths
to measure performance 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
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entropy label [RFC6790] values can be used in 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-MPLS Policy are outside the scope of this
document.
9. SR-MPLS Link Extended TE Metrics Advertisements
The extended TE metrics for SR-MPLS 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.
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. Backwards Compatibility
The procedures defined in this document are backwards compatible with
the procedures defined in [RFC6374] at both querier and responder
nodes. 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
This document describes the procedures for performance delay and loss
measurement for SR-MPLS networks, for both SR-MPLS Links and end-to-
end 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].
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12. IANA Considerations
IANA is requested to allocate a value for the following Mandatory
Return Path TLV Type for [RFC6374] to be carried in probe query
message from the "MPLS Loss/Delay Measurement TLV Object" registry
contained within the "Generic Associated Channel (G-ACh) Parameters"
registry set:
o Type TBA1: Return Path TLV
IANA is requested to create a sub-registry for "Return Path Sub-TLV
Type" for the Return Path TLV. All code points in the range 1
through 32759 in this registry shall be allocated according to the
"IETF Review" procedure as specified in [RFC8126]. Code points in
the range 32760 through 65279 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- 32767 | Mandatory TLV, | IETF Review |
| | unassigned | |
| 32768 - 65279 | Optional TLV, | First Come First Served |
| | unassigned | |
| 65280 - 65519 | Experimental | This document |
| 65520 - 65534 | Private Use | This document |
| 65535 | Reserved | This document |
+---------------+-------------------------+-------------------------+
Table 1: Return Path Sub-TLV Type Registry
IANA is requested to allocate the values for the following Sub-TLV
Types from this registry.
o Type (value 1): SR-MPLS Label Stack of the Reverse 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
probe query and response messages for loss measurement from the "MPLS
Loss/Delay Measurement TLV Object" registry contained within the
"Generic Associated Channel (G-ACh) Parameters" registry set:
o Type TBA2: Block Number TLV
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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>.
[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
[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>.
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[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>.
[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>.
[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-07 (work in progress),
May 2020.
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[I-D.voyer-pim-sr-p2mp-policy]
Voyer, D., Filsfils, C., Parekh, R., Bidgoli, H., and Z.
Zhang, "Segment Routing Point-to-Multipoint Policy",
draft-voyer-pim-sr-p2mp-policy-01 (work in progress),
April 2020.
[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-03
(work in progress), June 2020.
[I-D.shen-spring-p2mp-transport-chain]
Shen, Y., Zhang, Z., Parekh, R., Bidgoli, H., and Y.
Kamite, "Point-to-Multipoint Transport Using Chain
Replication in Segment Routing", draft-shen-spring-p2mp-
transport-chain-02 (work in progress), April 2020.
[I-D.ietf-pce-binding-label-sid]
Filsfils, C., Sivabalan, S., Tantsura, J., Hardwick, J.,
Previdi, S., and C. Li, "Carrying Binding Label/Segment-ID
in PCE-based Networks.", draft-ietf-pce-binding-label-
sid-03 (work in progress), June 2020.
[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, "MPLS Data Plane Encapsulation for In-situ
OAM Data", draft-gandhi-mpls-ioam-sr-02 (work in
progress), March 2020.
[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-02 (work
in progress), March 2020.
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Acknowledgments
The authors would like to thank Thierry Couture for the discussions
on the use-cases for the performance measurement in segment routing
networks. 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
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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