SPRING Working Group R. Gandhi, Ed.
Internet-Draft C. Filsfils
Intended status: Standards Track Cisco Systems, Inc.
Expires: January 7, 2022 D. Voyer
Bell Canada
M. Chen
Huawei
B. Janssens
Colt
R. Foote
Nokia
July 06, 2021
Performance Measurement Using Simple TWAMP (STAMP) for Segment Routing
Networks
draft-ietf-spring-stamp-srpm-00
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-ietf-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
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 January 7, 2022.
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Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
2.3. Reference Topology . . . . . . . . . . . . . . . . . . . 4
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5
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 . . . . . . . . 8
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 . . . . . . . . . . . . . . . . . . . . . . . . . 16
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 . . . . . . . . . . . . . . . . . . . . . 19
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
11.1. Normative References . . . . . . . . . . . . . . . . . . 19
11.2. Informative References . . . . . . . . . . . . . . . . . 19
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 22
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Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
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.ietf-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.ietf-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. 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
BSID: Binding Segment ID.
DM: Delay Measurement.
ECMP: Equal Cost Multi-Path.
HL: Hop Limit.
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HMAC: Hashed Message Authentication Code.
LM: Loss Measurement.
MPLS: Multiprotocol Label Switching.
NTP: Network Time Protocol.
OWAMP: One-Way Active Measurement Protocol.
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.
2.3. 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.
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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).
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.
The STAMP test packets require to be encapsulated to be transmitted
on a desired path under measurement. The base STAMP test packets can
be encapsulated using IP/UDP header and may use Destination UDP port
862 [RFC8762]. In this document, the STAMP packets using IP/UDP
header are considered for SR networks.
The STAMP test packets 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.
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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.ietf-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.ietf-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.
3.1. Example STAMP Reference Model
An example of a STAMP reference model with some of the typical
measurement parameters including the Destination UDP port for STAMP
test session is shown in the following Figure 1:
+------------+
| Controller |
+------------+
/ \
Destination UDP Port / \ Destination UDP Port
Authentication Mode / \ Authentication Mode
Key-chain / \ Key-chain
Timestamp Format / \ Timestamp Format
Packet Loss Type / \ Session-Reflector Mode
Delay Measurement Mode / \
v v
+-------+ +-------+
| | | |
| R1 |==========| R3 |
| | | |
+-------+ +-------+
STAMP Session-Sender STAMP Session-Reflector
Figure 1: Example STAMP Reference Model
A Destination UDP port number is selected as described in [RFC8762].
The same Destination UDP port can be used for STAMP test sessions for
link and end-to-end SR paths. In this case, the Destination UDP port
does not distinguish between link or end-to-end SR path measurements.
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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].
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].
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+---------------------------------------------------------------+
| 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 Destination Port | 862 .
. .
+---------------------------------------------------------------+
| Payload = Test Packet as specified in Section 3 of RFC 8972 |
. in Figure 1 and Figure 3 .
. .
+---------------------------------------------------------------+
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
Solicitation or other bootstrap method to find the IP address for the
links and refresh. SR encapsulation (e.g. adjacency SID of the link)
can be added for transmitting the STAMP test packets for links.
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 (the head-end of the SR Policy) IPv4 or IPv6
address MUST be used as the Source Address in the IP header of the
test packet. The STAMP Session-Reflector (the SR Policy endpoint)
IPv4 or IPv6 address MUST be used as the Destination Address in the
IP header of the test packet.
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.
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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 MUST be 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
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 MUST be 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
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in Section 4.1.1 in [RFC8986] is used to process the IPv6/UDP header
in the received test packets on the Session-Reflector.
+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Session-Sender IPv6 Address .
. Destination IP Address = Destination IPv6 Address .
. Protocol = UDP .
. .
+---------------------------------------------------------------+
| SRH as specified in RFC 8754 |
. <PSID, Segment List> .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Session-Sender .
. Destination Port = User-configured Destination Port | 862 .
. .
+---------------------------------------------------------------+
| Payload = Test Packet as specified in Section 3 of RFC 8972 |
. in Figure 1 and Figure 3 .
. .
+---------------------------------------------------------------+
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 3 of RFC 8972 |
. in Figure 2 and Figure 4 .
. .
+---------------------------------------------------------------+
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 MUST send its reachability path information to the STAMP
Session-Reflector using the Return Path TLV defined in
[I-D.ietf-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 transmits 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.ietf-ippm-stamp-srpm].
For two-way delay measurement mode for end-to-end SR paths, the STAMP
Session-Reflector transmits 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.ietf-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 .
. Protocol = UDP .
. .
+---------------------------------------------------------------+
| SRH as specified in RFC 8754 |
. <Segment List> .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Session-Reflector .
. Destination Port = Source Port from Received Test Packet .
. .
+---------------------------------------------------------------+
| Payload = Test Packet as specified in Section 3 of RFC 8972 |
. in Figure 2 and Figure 4 .
. .
+---------------------------------------------------------------+
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 (i.e. to slow path or control-
plane) at the STAMP Session-Reflector. In other words, the Session-
Reflector does not process them and generate Session-Reflector test
packets. This is a new measurement mode, not defined by STAMP
process [RFC8762].
The STAMP Session-Sender MUST set the Destination UDP port to the UDP
port it uses to receive the reply STAMP test packets. Since the
Session-Reflector does not support the STAMP process, the loopback
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function simply makes the necessary changes to the encapsulation
including IP and UDP headers to return the test packet to the
Session-Sender. The typical Session-Reflector test packet is not
used in this mode. The loopback function simply returns the received
Session-Sender test packet to the Session-Sender without STAMP
modifications defined in [RFC8762].
In case of SR-MPLS paths, the SR-MPLS header can contain the MPLS
label stack of the forward path or both forward and the reverse
paths. The IP header of the STAMP Session-Sender test packets MUST
set the Destination Address equal to the STAMP Session-Sender address
and the Source Address equal to the STAMP Session-Reflector address.
In case of SRv6 paths, the SRH can contain the Segment List of the
forward path or both forward and the reverse paths. In the former
case, an inner IPv6 header (after SRH and before UDP header) MUST be
added that contains the Destination Address equal to the STAMP
Session-Sender address and the Source Address equal to the STAMP
Session-Reflector address.
The Session-Sender may use the SSID field in the received reply test
packet or local configuration to identify its test session using the
loopback mode. In the received Session-Sender test packet at the
Session-Sender, the 'Session-Sender Sequence Number', 'Session-Sender
Timestamp', 'Session-Sender Error Estimate', and 'Session-Sender TTL'
fields are not present in this mode.
In this mode, as per Reference Topology, the test packet received
back at the Session-Sender retrieves the timestamp T1 from the test
packet and adds the received timestamp T4 locally. Both these
timestamps are used to measure the loopback delay as (T4 - T1). The
one-way delay can be derived using the loopback delay divided by two.
In loopback mode, the loopback delay includes the processing delay on
the Session-Reflector. The Session-Reflector processing delay
component includes 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:
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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 MUST be 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 MUST transmit its node
address in the Source Address of the reply test packets shown in
Figure 5. 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.
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4.4.1. TTL
The TTL field in the IPv4 and MPLS headers of the STAMP Session-
Sender and STAMP Session-Reflector test packet is set to 255 as per
Generalized TTL Security Mechanism (GTSM) [RFC5082].
4.4.2. IPv6 Hop Limit
The Hop Limit (HL) field in the IPv6 and SRH headers of the STAMP
Session-Sender and STAMP Session-Reflector test packet is set to 255
as per Generalized TTL Security Mechanism (GTSM) [RFC5082].
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. In the case of the loopback mode introduced
in this document, only the round-trip packet loss is applicable.
This method can be used for inferred packet loss measurement,
however, it provides only approximate view of the data packet loss.
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
SHOULD 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.
For SR-MPLS Policy, sweeping of MPLS entropy label [RFC6790] values
can be used in Session-Sender test packets and Session-Reflector test
packets to take advantage of the hashing function in forwarding plane
to influence the ECMP path taken by them.
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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.
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.ietf-ippm-stamp-srpm] MUST be
carried in the STAMP Session-Sender test packet to identify the
intended Session-Reflector, when using IPv4 Session-Reflector Address
from 127/8 range for a P2P SR Policy, when the STAMP test packet is
encapsulated by a tunneling protocol or an MPLS Segment List.
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.
The Security Considerations specified in [I-D.ietf-ippm-stamp-srpm]
are also equally applicable to the procedures defined in this
document.
When using the procedures defined in [RFC6936], the security
considerations specified in [RFC6936] also apply.
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10. IANA Considerations
This document does not require any IANA action.
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>.
[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>.
[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>.
[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.ietf-ippm-stamp-srpm]
Gandhi, R., Filsfils, C., Voyer, D., Chen, M., Janssens,
B., and R. Foote, "Simple TWAMP (STAMP) Extensions for
Segment Routing Networks", draft-ietf-ippm-stamp-srpm-00
(work in progress), June 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>.
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[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>.
[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C.
Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007,
<https://www.rfc-editor.org/info/rfc5082>.
[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>.
[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>.
[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>.
[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>.
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[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>.
[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-11 (work in progress),
April 2021.
[I-D.ietf-spring-sr-replication-segment]
Voyer, D., Filsfils, C., Parekh, R., Bidgoli, H., and Z.
Zhang, "SR Replication Segment for Multi-point Service
Delivery", draft-ietf-spring-sr-replication-segment-04
(work in progress), February 2021.
[I-D.ietf-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.
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[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. S. Luo, "Simple Two-way Active
Measurement Protocol (STAMP) Data Model", draft-ietf-ippm-
stamp-yang-07 (work in progress), March 2021.
[IEEE802.1AX]
IEEE Std. 802.1AX, "IEEE Standard for Local and
metropolitan area networks - Link Aggregation", November
2008.
Acknowledgments
The authors would like to thank Thierry Couture for the discussions
on the use-cases for 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
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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
Richard Foote
Nokia
Email: footer.foote@nokia.com
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