SPRING Working Group R. Gandhi, Ed.
Internet-Draft C. Filsfils
Intended status: Informational Cisco Systems, Inc.
Expires: October 31, 2021 D. Voyer
Bell Canada
M. Chen
Huawei
B. Janssens
Colt
R. Foote
Nokia
April 29, 2021
Performance Measurement Using Simple TWAMP (STAMP) for Segment Routing
Networks
draft-gandhi-spring-stamp-srpm-06
Abstract
Segment Routing (SR) leverages the source routing paradigm. SR is
applicable to both Multiprotocol Label Switching (SR-MPLS) and IPv6
(SRv6) data planes. This document describes procedures for
Performance Measurement in SR networks using the mechanisms defined
in RFC 8762 (Simple Two-Way Active Measurement Protocol (STAMP)) and
its optional extensions defined in RFC 8972 and further augmented in
draft-gandhi-ippm-stamp-srpm. The procedure described is applicable
to SR-MPLS and SRv6 data planes and is used for both links and end-
to-end SR paths including SR 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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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 October 31, 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
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
2.1. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Reference Topology . . . . . . . . . . . . . . . . . . . 4
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Example STAMP Reference Model . . . . . . . . . . . . . . 6
4. Delay Measurement for Links and SR Paths . . . . . . . . . . 7
4.1. Session-Sender Test Packet . . . . . . . . . . . . . . . 7
4.1.1. Session-Sender Test Packet for Links . . . . . . . . 7
4.1.2. Session-Sender Test Packet for SR Paths . . . . . . . 8
4.2. Session-Reflector Test Packet . . . . . . . . . . . . . . 10
4.2.1. One-way Measurement Mode . . . . . . . . . . . . . . 11
4.2.2. Two-way Measurement Mode . . . . . . . . . . . . . . 11
4.2.3. Loopback Measurement Mode . . . . . . . . . . . . . . 13
4.3. Delay Measurement for P2MP SR Policies . . . . . . . . . 14
4.4. Additional STAMP Test Packet Processing Rules . . . . . . 15
4.4.1. TTL . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.4.2. IPv6 Hop Limit . . . . . . . . . . . . . . . . . . . 16
4.4.3. Router Alert Option . . . . . . . . . . . . . . . . . 16
4.4.4. UDP Checksum . . . . . . . . . . . . . . . . . . . . 16
5. Packet Loss Measurement for Links and SR Paths . . . . . . . 16
6. Direct Measurement for Links and SR Paths . . . . . . . . . . 16
7. Session State for Links and SR Paths . . . . . . . . . . . . 17
8. ECMP Support for SR Policies . . . . . . . . . . . . . . . . 17
9. Security Considerations . . . . . . . . . . . . . . . . . . . 18
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
11.1. Normative References . . . . . . . . . . . . . . . . . . 19
11.2. Informative References . . . . . . . . . . . . . . . . . 19
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
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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 [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 [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).
The Simple Two-way Active Measurement Protocol (STAMP) provides
capabilities for the measurement of various performance metrics in IP
networks [RFC8762] without the use of a control channel to pre-signal
session parameters. [RFC8972] defines optional extensions for STAMP.
[I-D.gandhi-ippm-stamp-srpm] augments that framework to define STAMP
extensions for SR networks.
This document describes procedures for Performance Measurement in SR
networks using the mechanisms defined in STAMP [RFC8762] and its
optional extensions defined in [RFC8972] and further augmented in
[I-D.gandhi-ippm-stamp-srpm]. The procedure described is applicable
to SR-MPLS and SRv6 data planes and is used for both links and end-
to-end SR paths including SR Policies [RFC8402].
2. Conventions Used in This Document
2.1. Abbreviations
BSID: Binding Segment ID.
DM: Delay Measurement.
ECMP: Equal Cost Multi-Path.
HMAC: Hashed Message Authentication Code.
LM: Loss Measurement.
MPLS: Multiprotocol Label Switching.
NTP: Network Time Protocol.
OWAMP: One-Way Active Measurement Protocol.
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PM: Performance Measurement.
PSID: Path Segment Identifier.
PTP: Precision Time Protocol.
SHA: Secure Hash Algorithm.
SID: Segment ID.
SL: Segment List.
SR: Segment Routing.
SRH: Segment Routing Header.
SR-MPLS: Segment Routing with MPLS data plane.
SRv6: Segment Routing with IPv6 data plane.
SSID: STAMP Session Identifier.
STAMP: Simple Two-way Active Measurement Protocol.
TC: Traffic Class.
TTL: Time To Live.
2.2. Reference Topology
In the Reference Topology shown below, the STAMP Session-Sender R1
initiates a STAMP test packet and the STAMP Session-Reflector R3
transmits a reply test packet. The reply test packet may be
transmitted to the STAMP Session-Sender R1 on the same path (same set
of links and nodes) or a different path in the reverse direction from
the path taken towards the Session-Reflector.
The nodes R1 and R3 may be connected via a link or an SR path
[RFC8402]. The link may be a physical interface, virtual link, or
Link Aggregation Group (LAG) [IEEE802.1AX], or LAG member link. The
SR path may be an SR 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
/ \
+-------+ Test Packet +-------+
| | - - - - - - - - - ->| |
| R1 |=====================| R3 |
| |<- - - - - - - - - - | |
+-------+ Reply Test Packet +-------+
\ /
T4 T3
STAMP Session-Sender STAMP Session-Reflector
Reference Topology
3. Overview
For performance measurement in SR networks, the STAMP Session-Sender
and Session-Reflector test packets defined in [RFC8762] are used.
They are used in one-way, two-way (i.e. round-trip) and loopback
measurement modes. Note that one-way and round-trip are referred to
in [RFC8762] and are further described in this document because of
the introduction of loopback measurement mode in SR networks. The
procedures defined in this document are also used to infer packet
loss in SR networks.
The STAMP test packets are transmitted on the same path as the data
traffic flow under measurement to measure the delay and packet loss
experienced by the data traffic flow.
Typically, the STAMP test packets are transmitted along an IP path
between a Session-Sender and a Session-Reflector to measure delay and
packet loss along that IP path. Matching the forward and reverse
direction paths for STAMP test packets, even for directly connected
nodes is not guaranteed.
It may be desired in SR networks that the same path (same set of
links and nodes) between the Session-Sender and Session-Reflector be
used for the STAMP test packets in both directions. This is achieved
by using the optional STAMP extensions for SR-MPLS and SRv6 networks
specified in [I-D.gandhi-ippm-stamp-srpm]. The STAMP Session-
Reflector uses the return path parameters for the reply test packet
from the received STAMP test packet, as described in
[I-D.gandhi-ippm-stamp-srpm]. This way signaling and maintaining
dynamic SR network state for the STAMP sessions on the Session-
Reflector are avoided.
The optional STAMP extensions defined in [RFC8972] are used for
direct measurement packet loss in SR networks.
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3.1. Example STAMP Reference Model
An example of a STAMP reference model with some of the typical
measurement parameters including the Reflector UDP port for STAMP
test session is shown in the following Figure 1:
+------------+
| Controller |
+------------+
/ \
Reflector UDP Port / \ Reflector UDP Port
Authentication Mode / \ Authentication Mode
Key-chain / \ Key-chain
Timestamp Format / \ Timestamp Format
Packet Loss Type / \ Reflector Mode
Delay Measurement Mode / \
v v
+-------+ +-------+
| | | |
| R1 |==========| R3 |
| | | |
+-------+ +-------+
STAMP Session-Sender STAMP Session-Reflector
Figure 1: Example STAMP Reference Model
A reflector UDP port number is selected as described in [RFC8762].
The same reflector UDP port can be used for STAMP test sessions for
link and end-to-end SR paths. In this case, the reflector UDP port
does not distinguish between link or end-to-end SR path measurements.
Example of the Timestamp Format is Precision Time Protocol 64-bit
truncated (PTPv2) [IEEE1588] and Network Time Protocol (NTP). By
default, the Session-Reflector replies in kind to the timestamp
format received in the received Session-Sender test packet, as
indicated by the "Z" field in the Error Estimate field as described
in [RFC8762].
The Session-Reflector mode can be Stateful or Stateless as defined in
[RFC8762].
Example of Delay Measurement Mode is one-way, two-way (i.e. round-
trip) and loopback mode as described in this document.
Example of Packet Loss Type can be round-trip, near-end (forward) and
far-end (backward) packet loss as defined in [RFC8762].
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When using the authenticated mode for the STAMP test sessions, the
matching Authentication Type (e.g. HMAC-SHA-256) and Key-chain are
user-configured on STAMP Session-Sender and STAMP Session-Reflector
[RFC8762].
The controller shown in the example reference model is not intended
for the dynamic signaling of the SR parameters for STAMP test
sessions between the STAMP Session-Sender and STAMP Session-
Reflector.
Note that the YANG data model defined in [I-D.ietf-ippm-stamp-yang]
can be used to provision the STAMP Session-Sender and STAMP Session-
Reflector.
4. Delay Measurement for Links and SR Paths
4.1. Session-Sender Test Packet
The content of an example STAMP Session-Sender test packet using an
UDP header [RFC0768] is shown in Figure 2. The payload contains the
STAMP Session-Sender test packet defined in [RFC8762].
+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Session-Sender IPv4 or IPv6 Address .
. Destination IP Address=Session-Reflector IPv4 or IPv6 Address.
. Protocol = UDP .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Session-Sender .
. Destination Port = User-configured Reflector Port | 862 .
. .
+---------------------------------------------------------------+
| Payload = Test Packet as specified in Section 4.2 of RFC 8762 |
. .
+---------------------------------------------------------------+
Figure 2: Example Session-Sender Test Packet
4.1.1. Session-Sender Test Packet for Links
The STAMP Session-Sender test packet as shown in Figure 2 is
transmitted over the link under delay measurement. The local and
remote IP addresses of the link are used as Source and Destination
Addresses, respectively. For IPv6 links, the link local addresses
[RFC7404] can be used in the IPv6 header. The Session-Sender may use
the local Address Resolution Protocol (ARP) table, Neighbor
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Solicitation or other bootstrap method to find the IP address for the
links and refresh. An IPv4 address from the range 127/8 or IPv6
loopback address ::1/128 [RFC4291] must not be used to IP route test
packets in a network.
4.1.2. Session-Sender Test Packet for SR Paths
The delay measurement for end-to-end SR path in an SR network is
applicable to both end-to-end SR-MPLS and SRv6 paths including SR
Policies.
The STAMP Session-Sender IPv4 or IPv6 address is used as the Source
Address. The SR Policy endpoint IPv4 or IPv6 address is used as the
Destination Address.
In the case of Color-Only Destination Steering, with IPv4 endpoint of
0.0.0.0 or IPv6 endpoint of ::0
[I-D.ietf-spring-segment-routing-policy], the loopback address from
the range 127/8 for IPv4, or the loopback address ::1/128 for IPv6
[RFC4291] is used as the Session-Reflector Address, respectively.
4.1.2.1. Session-Sender Test Packet for SR-MPLS Policies
An SR-MPLS Policy may contain a number of Segment Lists (SLs). A
STAMP Session-Sender test packet is transmitted for each Segment List
of the SR-MPLS Policy. The content of an example STAMP Session-
Sender test packet for an end-to-end SR-MPLS Policy is shown in
Figure 3.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment(1) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment(n) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSID | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Test Packet as shown in Figure 2 |
. .
+---------------------------------------------------------------+
Figure 3: Example Session-Sender Test Packet for SR-MPLS Policy
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The Segment List can be empty in case of a single-hop SR-MPLS Policy
with Implicit NULL label.
The Path Segment Identifier (PSID)
[I-D.ietf-spring-mpls-path-segment] of an SR-MPLS Policy can be
carried in the MPLS header as shown in Figure 3, and can be used for
direct measurement as described in Section 6, titled "Direct
Measurement for Links and SR Paths".
4.1.2.2. Session-Sender Test Packet for SRv6 Policies
An SRv6 Policy may contain a number of Segment Lists. A STAMP
Session-Sender test packet is transmitted for each Segment List of
the SRv6 Policy. An SRv6 Policy can contain an SRv6 Segment Routing
Header (SRH) carrying a Segment List as described in [RFC8754]. The
content of an example STAMP Session-Sender test packet for an end-to-
end SRv6 Policy is shown in Figure 4.
The SRv6 network programming is described in [RFC8986]. The
procedure defined for Upper-Layer Header processing for SRv6 End SIDs
in Section 4.1.1 in [RFC8986] is used to process the IPv6/UDP header
in the received test packets on the Session-Reflector.
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+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Session-Sender IPv6 Address .
. Destination IP Address = Destination IPv6 Address .
. .
+---------------------------------------------------------------+
| SRH as specified in RFC 8754 |
. <PSID, Segment List> .
. .
+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Session-Sender IPv6 Address .
. Destination IP Address = Session-Reflector IPv6 Address .
. Protocol = UDP .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Session-Sender .
. Destination Port = User-configured Reflector Port | 862 .
. .
+---------------------------------------------------------------+
| Payload = Test Packet as specified in Section 4.2 of RFC 8762 |
. .
+---------------------------------------------------------------+
Figure 4: Example Session-Sender Test Packet for SRv6 Policy
The Segment List (SL) may be empty and no SRH may be carried.
The Path Segment Identifier (PSID)
[I-D.ietf-spring-srv6-path-segment] of the SRV6 Policy can be carried
in the SRH as shown in Figure 4 and can be used for direct
measurement as described in Section 6, titled "Direct Measurement for
Links and SR Paths".
4.2. Session-Reflector Test Packet
The STAMP Session-Reflector reply test packet uses the IP/UDP
information from the received test packet as shown in Figure 5.
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+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Session-Reflector IPv4 or IPv6 Address .
. Destination IP Address .
. = Source IP Address from Received Test Packet .
. Protocol = UDP .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Session-Reflector .
. Destination Port = Source Port from Received Test Packet .
. .
+---------------------------------------------------------------+
| Payload = Test Packet as specified in Section 4.3 of RFC 8762 |
. .
+---------------------------------------------------------------+
Figure 5: Example Session-Reflector Test Packet
4.2.1. One-way Measurement Mode
In one-way delay measurement mode, a reply test packet as shown in
Figure 5 is transmitted by the STAMP Session-Reflector, for both
links and end-to-end SR Policies. The reply test packet may be
transmitted on the same path or a different path in the reverse
direction.
The STAMP Session-Sender address may not be reachable via IP route
from the STAMP Session-Reflector. The STAMP Session-Sender in this
case can send its reachability path information to the STAMP Session-
Reflector using the Return Path TLV defined in
[I-D.gandhi-ippm-stamp-srpm].
In this mode, as per Reference Topology, all timestamps T1, T2, T3,
and T4 are collected by the test packets. However, only timestamps
T1 and T2 are used to measure one-way delay as (T2 - T1). The one-
way delay measurement mode requires the clock on the Session-Sender
and Session-Reflector to be synchronized.
4.2.2. Two-way Measurement Mode
In two-way (i.e. round-trip) delay measurement mode, a reply test
packet as shown in Figure 5 is transmitted by the STAMP Session-
Reflector on the same path in the reverse direction, e.g. on the
reverse direction link or associated reverse SR path
[I-D.ietf-pce-sr-bidir-path].
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For two-way delay measurement mode for links, the STAMP Session-
Reflector needs to transmit the reply test packet on the same link
where the test packet is received. The STAMP Session-Sender can
request in the test packet to the STAMP Session-Reflector to transmit
the reply test packet back on the same link using the Control Code
Sub-TLV in the Return Path TLV defined in
[I-D.gandhi-ippm-stamp-srpm].
For two-way delay measurement mode for end-to-end SR paths, the STAMP
Session-Reflector needs to transmit the reply test packet on a
specific reverse path. The STAMP Session-Sender can request in the
test packet to the STAMP Session-Reflector to transmit the reply test
packet back on a given reverse path using a Segment List sub-TLV in
the Return Path TLV defined in [I-D.gandhi-ippm-stamp-srpm].
In this mode, as per Reference Topology, all timestamps T1, T2, T3,
and T4 are collected by the test packets. All four timestamps are
used to measure two-way delay as ((T4 - T1) - (T3 - T2)). When clock
synchronization on the Session-Sender and Session-Reflector nodes is
not possible, the one-way delay can be derived using two-way delay
divided by two.
4.2.2.1. Session-Reflector Test Packet for SR-MPLS Policies
The content of an example STAMP Session-Reflector reply test packet
transmitted on the same path as the data traffic flow under
measurement for two-way delay measurement of an end-to-end SR-MPLS
Policy 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment(1) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment(n) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Test Packet as shown in Figure 5 |
. .
+---------------------------------------------------------------+
Figure 6: Example Session-Reflector Test Packet for SR-MPLS Policy
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4.2.2.2. Session-Reflector Test Packet for SRv6 Policies
The content of an example STAMP Session-Reflector reply test packet
transmitted on the same path as the data traffic flow under
measurement for two-way delay measurement of an end-to-end SRv6
Policy with SRH is shown in Figure 7.
The procedure defined for Upper-Layer Header processing for SRv6 End
SIDs in Section 4.1.1 in [RFC8986] is used to process the IPv6/UDP
header in the received reply test packets on the Session-Sender.
+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Session-Reflector IPv6 Address .
. Destination IP Address = Destination IPv6 Address .
. .
+---------------------------------------------------------------+
| SRH as specified in RFC 8754 |
. <Segment List> .
. .
+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Session-Reflector IPv6 Address .
. Destination IP Address .
. = Source IPv6 Address from Received Test Packet .
. Protocol = UDP .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Session-Reflector .
. Destination Port = Source Port from Received Test Packet .
. .
+---------------------------------------------------------------+
| Payload = Test Packet as specified in Section 4.3 of RFC 8762 |
. .
+---------------------------------------------------------------+
Figure 7: Example Session-Reflector Test Packet for SRv6 Policy
4.2.3. Loopback Measurement Mode
The STAMP Session-Sender test packets are transmitted in loopback
mode to measure loopback delay of a bidirectional circular path. In
this mode, the received Session-Sender test packets are not punted
out of the fast path in forwarding (to slow path or control-plane) at
the STAMP Session-Reflector. In other words, the Session-Reflector
does not process them and generate reply test packets.
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The IP header of the STAMP Session-Sender test packet contains the
Destination Address equals to the STAMP Session-Sender address and
the Source Address equals to the STAMP Session-Reflector address.
The Session-Sender sets the Reflector UDP port that it uses to
receive the test packet. Optionally, the STAMP Session-Sender test
packet can carry the return path information (e.g. return path label
stack for SR-MPLS) as part of the SR header.
The Session-Sender can use the SSID field in the reply test packet
and/ or local configuration to know that the test session is using
the loopback mode. As the reply test packet is not generated by the
STAMP Session-Reflector, the STAMP Session-Sender ignores the
'Session-Sender Sequence Number', 'Session-Sender Timestamp',
'Session-Sender Error Estimate', and 'Session-Sender TTL' in the
received test packet. The Session-Sender sets these fields to 0 upon
transmission.
In this mode, as per Reference Topology, the timestamps T1 and T4 are
collected by the test packets. Both these timestamps are used to
measure loopback delay as (T4 - T1). When STAMP capability on the
Session-Reflector node is not possible, the one-way delay can be
derived using loopback delay divided by two. In this mode, the
responder node processing time component reflects only the time
required to loop the test packet from the incoming interface to the
outgoing interface in forwarding plane.
4.3. Delay Measurement for P2MP SR Policies
The Point-to-Multipoint (P2MP) SR path that originates from a root
node terminates on multiple destinations called leaf nodes (e.g.
P2MP SR 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 Policies are also equally applicable
to the P2MP SR Policies. The procedure for one-way measurement is
defined as following:
o The STAMP Session-Sender root node transmits test packets 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 STAMP Session-Sender
test packets may contain the replication SID as defined in
[I-D.ietf-spring-sr-replication-segment].
o The Destination Address is set to the loopback address from the
range 127/8 for IPv4, or the loopback address ::1/128 for IPv6.
o Each STAMP Session-Reflector leaf node transmits its node address
in the Source Address of the reply test packets shown in Figure 5.
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This allows the STAMP Session-Sender root node to identify the
STAMP Session-Reflector leaf nodes of the P2MP SR Policy.
o The P2MP root node measures the delay for each P2MP leaf node
individually.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Test Packet as shown in Figure 2 |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Example Session-Sender Test Packet with Tree-SID for SR-
MPLS Policy
The considerations for two-way mode for P2MP SR Policy (e.g. for co-
routed bidirectional SR-MPLS path) are outside the scope of this
document.
4.4. Additional STAMP Test Packet Processing Rules
The processing rules described in this section are applicable to the
STAMP test packets for links and end-to-end SR paths including SR
Policies.
4.4.1. TTL
The TTL field in the IPv4 and MPLS headers of the STAMP Session-
Sender and STAMP Session-Reflector test packets is set to 255, except
in the following cases.
When using the Session-Reflector IPv4 Address from the range 127/8,
the TTL field in the IPv4 header is set to 1, for otherwise,
encapsulated packets.
For link delay, the TTL field in the STAMP test packet is set to 1 in
one-way and two-way delay measurement modes.
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4.4.2. IPv6 Hop Limit
The Hop Limit field in the IPv6 and SRH headers of the STAMP Session-
Sender and STAMP Session-Reflector test packets is set to 255, except
in the following cases.
When using the Session-Reflector IPv6 Address of loopback address
::1/128, the Hop Limit field in the IPv6 header is set to 1, for
otherwise, encapsulated packets.
For link delay, the Hop Limit field in the STAMP test packet is set
to 1 in one-way and two-way delay measurement modes.
4.4.3. Router Alert Option
The Router Alert IP option (RAO) [RFC2113] is not set in the STAMP
test packets for links and end-to-end SR paths.
4.4.4. UDP Checksum
For IPv4 test packets, where the hardware is not capable of re-
computing the UDP checksum or adding checksum complement [RFC7820],
the Session-Sender may set the UDP checksum value to 0 [RFC8085].
For IPv6 test packets, where the hardware is not capable of re-
computing the UDP checksum or adding checksum complement [RFC7820],
the Session-Sender and Session-Reflector may use the procedure
defined in [RFC6936] for the UDP checksum.
5. Packet Loss Measurement for Links and SR Paths
The procedure described in Section 4 for delay measurement using
STAMP test packets can be used to detect (test) packet loss for links
and end-to-end SR paths. The Sequence Number field in the STAMP test
packet is used as described in Section 4 "Theory of Operation" where
Stateful and Stateless Session-Reflector operations are defined
[RFC8762], to detect round-trip, near-end (forward) and far-end
(backward) packet loss.
This method can be used for inferred packet loss measurement,
however, it does not provide accurate data packet loss metric.
6. Direct Measurement for Links and SR Paths
The STAMP "Direct Measurement" TLV (Type 5) defined in [RFC8972] can
be used in SR networks for data packet loss measurement. The STAMP
test packets with this TLV are transmitted using the procedures
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described in Section 4 to collect the transmit and receive counters
of the data flow for the links and end-to-end SR paths.
The PSID carried in the received data packet for the traffic flow
under measurement can be used to measure receive data packets (for
receive traffic counter) for an end-to-end SR path on the STAMP
Session-Reflector. The PSID in the received Session-Sender test
packet header can be used to associate the receive traffic counter on
the Session-Reflector for the end-to-end SR path.
The STAMP "Direct Measurement" TLV (Type 5) lacks the support to
identify the Block Number of the Direct Measurement traffic counters,
which is required for Alternate-Marking Method [RFC8321] for accurate
data packet loss metric.
7. Session State for Links and SR Paths
The STAMP test session state allows to know if the performance
measurement test is active. The threshold-based notification may not
be generated if the delay values do not change significantly. For an
unambiguous monitoring, the controller needs to distinguish the cases
whether the performance measurement is active, or delay values are
not changing to cross threshold.
The STAMP test session state initially is declared active when one or
more reply test packets are received at the STAMP Session-Sender.
The STAMP test session state is declared idle (or failed) when
consecutive N number of reply test packets are not received at the
STAMP Session-Sender, where N is locally provisioned value.
8. ECMP Support for SR Policies
An SR Policy can have ECMPs between the source and transit nodes,
between transit nodes and between transit and destination nodes.
Usage of Anycast SID [RFC8402] by an SR Policy can result in ECMP
paths via transit nodes part of that Anycast group. The test packets
need to be transmitted to traverse different ECMP paths to measure
end-to-end delay of an SR Policy.
Forwarding plane has various hashing functions available to forward
packets on specific ECMP paths. The mechanisms described in
[RFC8029] and [RFC5884] for handling ECMPs are also applicable to the
delay measurement.
In IPv4 header of the STAMP Session-Sender test packets, sweeping of
Session-Reflector Address from the range 127/8 can be used to
exercise ECMP paths. In this case, both the forward and the return
paths must be SR-MPLS paths when using the loopback mode.
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As specified in [RFC6437], Flow Label field in the outer IPv6 header
can also be used for sweeping to exercise different IPv6 ECMP paths.
The "Destination Node Address" TLV [I-D.gandhi-ippm-stamp-srpm] can
be carried in the STAMP Session-Sender test packet to identify the
intended Session-Reflector, for example, in case of using IPv4
Session-Reflector Address from 127/8 range when the STAMP test packet
is encapsulated by a tunneling protocol or an MPLS Segment list. The
STAMP Session-Reflector must not transmit reply test packet if it is
not the intended destination node in the "Destination Node Address"
TLV [I-D.gandhi-ippm-stamp-srpm].
9. Security Considerations
The performance measurement is intended for deployment in well-
managed private and service provider networks. As such, it assumes
that a node involved in a measurement operation has previously
verified the integrity of the path and the identity of the far-end
STAMP Session-Reflector.
If desired, attacks can be mitigated by performing basic validation
and sanity checks, at the STAMP Session-Sender, of the counter or
timestamp fields in received measurement reply test packets. The
minimal state associated with these protocols also limits the extent
of measurement disruption that can be caused by a corrupt or invalid
packet to a single test cycle.
Use of HMAC-SHA-256 in the authenticated mode protects the data
integrity of the test packets. SRv6 has HMAC protection
authentication defined for SRH [RFC8754]. Hence, test packets for
SRv6 may not need authentication mode. Cryptographic measures may be
enhanced by the correct configuration of access-control lists and
firewalls.
The security considerations specified in [RFC8762] and [RFC8972] also
apply to the procedures described in this document.
When using the procedures defined in [RFC6936], the security
considerations specified in [RFC6936] also apply.
10. IANA Considerations
This document does not require any IANA action.
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11. References
11.1. Normative References
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980,
<https://www.rfc-editor.org/info/rfc768>.
[RFC8762] Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple
Two-Way Active Measurement Protocol", RFC 8762,
DOI 10.17487/RFC8762, March 2020,
<https://www.rfc-editor.org/info/rfc8762>.
[RFC8972] Mirsky, G., Min, X., Nydell, H., Foote, R., Masputra, A.,
and E. Ruffini, "Simple Two-Way Active Measurement
Protocol Optional Extensions", RFC 8972,
DOI 10.17487/RFC8972, January 2021,
<https://www.rfc-editor.org/info/rfc8972>.
[I-D.gandhi-ippm-stamp-srpm]
Gandhi, R., Filsfils, C., Voyer, D., Chen, M., and B.
Janssens, "Simple TWAMP (STAMP) Extensions for Segment
Routing Networks", draft-gandhi-ippm-stamp-srpm-03 (work
in progress), April 2021.
11.2. Informative References
[IEEE1588]
IEEE, "1588-2008 IEEE Standard for a Precision Clock
Synchronization Protocol for Networked Measurement and
Control Systems", March 2008.
[RFC2113] Katz, D., "IP Router Alert Option", RFC 2113,
DOI 10.17487/RFC2113, February 1997,
<https://www.rfc-editor.org/info/rfc2113>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>.
[RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
"Bidirectional Forwarding Detection (BFD) for MPLS Label
Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884,
June 2010, <https://www.rfc-editor.org/info/rfc5884>.
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[RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme,
"IPv6 Flow Label Specification", RFC 6437,
DOI 10.17487/RFC6437, November 2011,
<https://www.rfc-editor.org/info/rfc6437>.
[RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement
for the Use of IPv6 UDP Datagrams with Zero Checksums",
RFC 6936, DOI 10.17487/RFC6936, April 2013,
<https://www.rfc-editor.org/info/rfc6936>.
[RFC7404] Behringer, M. and E. Vyncke, "Using Only Link-Local
Addressing inside an IPv6 Network", RFC 7404,
DOI 10.17487/RFC7404, November 2014,
<https://www.rfc-editor.org/info/rfc7404>.
[RFC7820] Mizrahi, T., "UDP Checksum Complement in the One-Way
Active Measurement Protocol (OWAMP) and Two-Way Active
Measurement Protocol (TWAMP)", RFC 7820,
DOI 10.17487/RFC7820, March 2016,
<https://www.rfc-editor.org/info/rfc7820>.
[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
Switched (MPLS) Data-Plane Failures", RFC 8029,
DOI 10.17487/RFC8029, March 2017,
<https://www.rfc-editor.org/info/rfc8029>.
[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>.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <https://www.rfc-editor.org/info/rfc8085>.
[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>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
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[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>.
[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-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-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-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.
[I-D.ietf-spring-srv6-path-segment]
Li, C., Cheng, W., Chen, M., Dhody, D., and R. Gandhi,
"Path Segment for SRv6 (Segment Routing in IPv6)", draft-
ietf-spring-srv6-path-segment-00 (work in progress),
November 2020.
[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.ietf-ippm-stamp-yang]
Mirsky, G., Min, X., and W. Luo, "Simple Two-way Active
Measurement Protocol (STAMP) Data Model", draft-ietf-ippm-
stamp-yang-07 (work in progress), March 2021.
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[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 Performance Measurement in segment routing. The
authors would also like to thank Greg Mirsky, Gyan Mishra, Xie
Jingrong, and Mike Koldychev for reviewing this document and
providing useful comments and suggestions. Patrick Khordoc and Radu
Valceanu have helped improve the mechanisms described in this
document.
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
Mach(Guoyi) Chen
Huawei
Email: mach.chen@huawei.com
Bart Janssens
Colt
Email: Bart.Janssens@colt.net
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Richard Foote
Nokia
Email: footer.foote@nokia.com
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