Internet DRAFT - draft-gandhi-spring-twamp-srpm
draft-gandhi-spring-twamp-srpm
SPRING Working Group R. Gandhi, Ed.
Internet-Draft C. Filsfils
Intended status: Standards Track Cisco Systems, Inc.
Expires: April 24, 2021 D. Voyer
Bell Canada
M. Chen
Huawei
B. Janssens
Colt
October 21, 2020
Performance Measurement Using TWAMP Light for Segment Routing Networks
draft-gandhi-spring-twamp-srpm-11
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 specifies procedure for sending
and processing probe query and response messages for Performance
Measurement (PM) in Segment Routing networks. The procedure uses the
mechanisms defined in RFC 5357 (Two-Way Active Measurement Protocol
(TWAMP) Light) and its extensions for Performance Measurement. The
procedure specified 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
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 24, 2021.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
2.3. Reference Topology . . . . . . . . . . . . . . . . . . . 4
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Example Provisioning Model . . . . . . . . . . . . . . . 6
4. Probe Messages . . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Probe Query Message . . . . . . . . . . . . . . . . . . . 7
4.1.1. Delay Measurement Query Message . . . . . . . . . . . 7
4.1.2. Loss Measurement Query Message . . . . . . . . . . . 8
4.1.3. Probe Query for Links . . . . . . . . . . . . . . . . 9
4.1.4. Probe Query for SR Policy . . . . . . . . . . . . . . 9
4.2. Probe Response Message . . . . . . . . . . . . . . . . . 11
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. Additional Probe Message Processing Rules . . . . . . . . 14
4.3.1. TTL and Hop Limit . . . . . . . . . . . . . . . . . . 14
4.3.2. Router Alert Option . . . . . . . . . . . . . . . . . 14
4.3.3. UDP Checksum . . . . . . . . . . . . . . . . . . . . 14
5. Performance Measurement for P2MP SR Policies . . . . . . . . 14
6. ECMP Support for SR Policies . . . . . . . . . . . . . . . . 16
7. Performance Delay and Liveness Monitoring . . . . . . . . . . 16
8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
10.1. Normative References . . . . . . . . . . . . . . . . . . 17
10.2. Informative References . . . . . . . . . . . . . . . . . 17
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
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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. 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 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 using probe messages. These protocols rely on
control-channel signaling to establish a test-channel over an UDP
path. The TWAMP Light [Appendix I in RFC5357] [BBF.TR-390] provides
simplified mechanisms for active performance measurement in Customer
IP networks by provisioning UDP paths and eliminates the need for
control-channel signaling.
This document specifies procedures for sending and processing probe
query and response messages for Performance Measurement in SR
networks. The procedure uses the mechanisms defined in [RFC5357]
(TWAMP Light) and its extensions for Performance Measurement. The
procedure specified is applicable to SR-MPLS and SRv6 data planes and
is used for both Links and end-to-end SR Paths including SR Policies
and Flex-Algo IGP Paths. Unless otherwise specified, the mechanisms
defined in [RFC5357] are not modified by this document.
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.
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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.
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.
TC: Traffic Class.
TWAMP: Two-Way Active Measurement Protocol.
2.3. Reference Topology
In the reference topology shown below, the sender node R1 initiates a
performance measurement probe query message and the reflector node R5
sends a probe response message for the query message received. The
probe response message is typically sent to the sender node R1.
SR is enabled on nodes R1 and R5. The nodes R1 and R5 may be
directly connected via a Link or there exists a Point-to-Point (P2P)
SR Path e.g. SR Policy [I-D.ietf-spring-segment-routing-policy] on
node R1 (called head-end) with destination to node R5 (called tail-
end).
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t1 t2
/ \
+-------+ Query +-------+
| | - - - - - - - - - ->| |
| R1 |=====================| R5 |
| |<- - - - - - - - - - | |
+-------+ Response +-------+
\ /
t4 t3
Sender Reflector
Reference Topology
3. Overview
For one-way and two-way delay measurements in Segment Routing
networks, the probe messages defined in [RFC5357] are used. For
direct-mode and inferred-mode loss measurements, the probe messages
defined in [I-D.gandhi-ippm-twamp-srpm] are used. For both Links and
end-to-end SR Paths including SR Policies and Flex-Algo IGP Paths, no
PM state for delay or loss measurement need to be created on the
reflector node R5.
Separate UDP destination port numbers are user-configured for delay
and loss measurements. As specified in [RFC8545], the reflector
supports the destination UDP port 862 for delay measurement probe
messages by default. This UDP port however, is not used for loss
measurement probe messages. The sender uses the UDP port number
following the guidelines specified in Section 6 in [RFC6335]. The
same destination UDP port is used for Links and SR Paths and the
reflector is unaware if the query is for the Links or SR Paths. The
number of UDP ports with PM functionality needs to be minimized due
to limited hardware resources.
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 sender node, and are
used to measure the delay experienced by the actual data traffic
flowing on the Links and SR Paths.
o For loss measurement, the probe messages are sent on the congruent
path of the data traffic by the sender 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
reflector node (incoming link or incoming SID needed since the
reflector node does not have PM state present).
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The In-Situ Operations, Administration, and Maintenance (IOAM)
mechanisms for SR-MPLS defined in [I-D.gandhi-mpls-ioam-sr] and for
SRv6 defined in [I-D.ali-spring-ioam-srv6] are used to carry PM
information such as timestamp in-band as part of the data packets,
and are outside the scope of this document.
3.1. Example Provisioning Model
An example of a provisioning model and typical measurement parameters
for each user-configured destination UDP port for performance delay
and loss measurements is shown in the following Figure 1:
+------------+
| Controller |
+------------+
Destination UDP Port / \ Destination UDP port
Measurement Protocol / \ Measurement Protocol
Measurement Type / \ Measurement Type
Delay/Loss / \ Delay/Loss
Authentication Mode & Key / \ Authentication Mode & Key
Timestamp Format / \ Loss Measurement Mode
Delay Measurement Mode / \
Loss Measurement Mode / \
v v
+-------+ +-------+
| | | |
| R1 |============| R5 |
| | SR Path | |
+-------+ Or Link +-------+
Sender Reflector
Figure 1: Example Provisioning Model
Example of Measurement Protocol is TWAMP Light, example of the
Timestamp Format is PTPv2 [IEEE1588] or NTP and example of the Loss
Measurement mode is inferred-mode or direct-mode.
The mechanisms to provision the sender and reflector nodes are
outside the scope of this document. The provisioning model is not
used for signaling the PM parameters between the reflector and sender
nodes in SR networks.
The reflector node R5 uses the parameters for the timestamp format
and delay measurement mode (i.e. one-way or two-way mode) from the
received probe query message.
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4. Probe Messages
4.1. Probe Query Message
The probe messages defined in [RFC5357] are used for delay
measurement for Links and end-to-end SR Paths including SR Policies.
For loss measurement, the probe messages defined in [I-D.gandhi-ippm-
twamp-srpm] are used.
4.1.1. Delay Measurement Query Message
The message content for delay measurement probe query message using
UDP header [RFC0768] is shown in Figure 2. The DM probe query
message is sent with user-configured Destination UDP port number for
DM. The Destination UDP port cannot be used as Source port, since
the message does not have any indication to distinguish between the
query and response message. The payload of the DM probe query
message contains the delay measurement message defined in
Section 4.1.2 of [RFC5357]. For symmetrical size query and response
messages as defined in [RFC6038], the DM probe query message contains
the payload format defined in Section 4.2.1 of [RFC5357].
+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Sender IPv4 or IPv6 Address .
. Destination IP Address = Reflector IPv4 or IPv6 Address .
. Protocol = UDP .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Sender .
. Destination Port = User-configured Port for Delay Measurement.
. .
+---------------------------------------------------------------+
| Payload = DM Message as specified in Section 4.2.1 of RFC 5357|
. Payload = DM Message as specified in Section 4.1.2 of RFC 5357.
. .
+---------------------------------------------------------------+
Figure 2: DM Probe Query Message
Timestamp field is eight bytes and use the format defined in
Section 4.2.1 of [RFC5357]. It is recommended to use the IEEE 1588v2
Precision Time Protocol (PTP) truncated 64-bit timestamp format
[IEEE1588] as specified in [RFC8186], with hardware support in
Segment Routing networks.
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4.1.1.1. Delay Measurement Authentication Mode
When using the authenticated mode for delay measurement, the matching
authentication type (e.g. HMAC-SHA-256) and key are user-configured
on both the sender and reflector nodes. A separate user-configured
destination UDP port is used for the delay measurement in
authentication mode due to the different probe message format.
4.1.2. Loss Measurement Query Message
The message content for loss measurement probe query message using
UDP header [RFC0768] is shown in Figure 3. The LM probe query
message is sent with user-configured Destination UDP port number for
LM, which is a different Destination UDP port number than DM.
Separate Destination UDP ports are used for direct-mode and inferred-
mode loss measurements. The Destination UDP port cannot be used as
Source port, since the message does not have any indication to
distinguish between the query and response message. The LM probe
query message contains the payload for loss measurement as defined in
[I-D.gandhi-ippm-twamp-srpm].
+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Sender IPv4 or IPv6 Address .
. Destination IP Address = Reflector IPv4 or IPv6 Address .
. Protocol = UDP .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Sender .
. Destination Port = User-configured Port for Loss Measurement .
. .
+---------------------------------------------------------------+
| Payload = LM Message specified in [I-D.gandhi-ippm-twamp-srpm]|
. .
+---------------------------------------------------------------+
Figure 3: LM Probe Query Message
4.1.2.1. Loss Measurement Authentication Mode
When using the authenticated mode for loss measurement, the matching
authentication type (e.g. HMAC-SHA-256) and key are user-configured
on both the sender and reflector nodes. A separate user-configured
destination UDP port is used for the loss measurement in
authentication mode due to the different message format.
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4.1.3. Probe Query for Links
The probe query message as defined in Figure 2 for delay measurement
and Figure 3 for loss measurement are used for Links which may be
physical, virtual or LAG (bundle), LAG (bundle) member, numbered/
unnumbered Links. The probe messages are pre-routed over the Link
for both delay and loss measurement. The local and remote IP
addresses of the link are used as Source and Destination Addresses.
They can also be IPv6 link local address as probe messages are pre-
routed.
4.1.4. Probe Query for SR Policy
The performance delay and loss measurement for segment routing is
applicable to both end-to-end SR-MPLS and SRv6 Policies.
The sender IPv4 or IPv6 address is used as the source address. The
endpoint IPv4 or IPv6 address is used as the destination address. In
the case of SR Policy with IPv4 endpoint of 0.0.0.0 or IPv6 endpoint
of ::0 [I-D.ietf-spring-segment-routing-policy], the loopback address
from range 127/8 for IPv4, or the loopback address ::1/128 for IPv6
is used as the destination address, respectively.
4.1.4.1. Probe Query Message for SR-MPLS Policy
The probe query messages for performance measurement of an end-to-end
SR-MPLS Policy is sent using its SR-MPLS header containing the MPLS
segment list as shown in Figure 4.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment(1) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment(n) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSID | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message as shown in Figure 2 for DM or Figure 3 for LM |
. .
+---------------------------------------------------------------+
Figure 4: Example Probe Query Message for SR-MPLS Policy
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The Segment List (SL) can be empty to indicate Implicit NULL label
case for a single-hop SR Policy.
The Path Segment Identifier (PSID)
[I-D.ietf-spring-mpls-path-segment] of the SR-MPLS Policy is used for
accounting received traffic on the egress node for loss measurement.
4.1.4.2. Probe Query Message for SRv6 Policy
An SRv6 Policy setup using the SRv6 Segment Routing Header (SRH) and
a Segment List as defined in [RFC8754]. The SRv6 network programming
is defined in [I-D.ietf-spring-srv6-network-programming]. The probe
query messages for performance measurement of an end-to-end SRv6
Policy is sent using its SRH with Segment List as shown in Figure 5.
The procedure defined for upper-layer header processing for SRv6 SIDs
in [I-D.ietf-spring-srv6-network-programming] is used to process the
UDP header in the received probe query messages.
+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Sender IPv6 Address .
. Destination IP Address = Destination IPv6 Address .
. .
+---------------------------------------------------------------+
| SRH as specified in RFC 8754 |
. <Segment List> .
. .
+---------------------------------------------------------------+
| IP Header (as needed) |
. Source IP Address = Sender IPv6 Address .
. Destination IP Address = Reflector IPv6 Address .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Sender .
. Destination Port = User-configured Port .
. .
+---------------------------------------------------------------+
| Payload = DM Message as specified in Section 4.2.1 of RFC 5357|
. Payload = DM Message as specified in Section 4.1.2 of RFC 5357.
. Payload = LM Message specified in [I-D.gandhi-ippm-twamp-srpm].
. .
+---------------------------------------------------------------+
Figure 5: Example Probe Query Message for SRv6 Policy
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4.2. Probe Response Message
The probe response message is sent using the IP/UDP information from
the received probe query message. The content of the probe response
message is shown in Figure 6.
+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Reflector IPv4 or IPv6 Address .
. Destination IP Address = Source IP Address from Query .
. Protocol = UDP .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Reflector .
. Destination Port = Source Port from Query .
. .
+---------------------------------------------------------------+
| Payload = DM Message as specified in Section 4.2.1 of RFC 5357|
. Payload = LM Message specified in [I-D.gandhi-ippm-twamp-srpm].
. .
+---------------------------------------------------------------+
Figure 6: Probe Response Message
4.2.1. One-way Measurement Mode
In one-way measurement mode, the probe response message as defined in
Figure 6 is sent back out-of-band to the sender node, for both Links
and SR Policies. The Sender Control Code is set to "Out-of-band
Response Requested". In this delay measurement mode, as per
Reference Topology, all timestamps t1, t2, t3, and t4 are collected
by the probes. However, only timestamps t1 and t2 are used to
measure one-way delay as (t2 - t1).
4.2.2. Two-way Measurement Mode
In two-way measurement mode, when using a bidirectional path, the
probe response message as defined in Figure 6 is sent back to the
sender node on the congruent path of the data traffic on the same
reverse direction Link or associated reverse SR Policy
[I-D.ietf-pce-sr-bidir-path]. The Sender Control Code 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
as ((t4 - t1) - (t3 - t2)).
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For two-way measurement mode for Links, the probe response message is
sent back on the incoming physical interface where the probe query
message is received.
4.2.2.1. Probe Response Message for SR-MPLS Policy
The message content for sending probe response message for two-way
performance measurement of an end-to-end SR-MPLS Policy 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment(1) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment(n) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message as shown in Figure 6 |
. .
+---------------------------------------------------------------+
Figure 7: Example Probe Response Message for SR-MPLS Policy
The Path Segment Identifier (PSID)
[I-D.ietf-spring-mpls-path-segment] of the forward SR Policy in the
probe query can be used to find the associated reverse SR Policy
[I-D.ietf-pce-sr-bidir-path] to send the probe response message for
two-way measurement of SR Policy.
4.2.2.2. Probe Response Message for SRv6 Policy
The message content for sending probe response message on the
congruent path of the data traffic for two-way performance
measurement of an end-to-end SRv6 Policy with SRH is shown in
Figure 8. The procedure defined for upper-layer header processing
for SRv6 SIDs in [I-D.ietf-spring-srv6-network-programming] is used
to process the UDP header in the received probe response messages.
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+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Reflector IPv6 Address .
. Destination IP Address = Destination IPv6 Address .
. .
+---------------------------------------------------------------+
| SRH as specified in RFC 8754 |
. <Segment List> .
. .
+---------------------------------------------------------------+
| IP Header (as needed) |
. Source IP Address = Reflector IPv6 Address .
. Destination IP Address = Source IPv6 Address from Query .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Sender .
. Destination Port = User-configured Port .
. .
+---------------------------------------------------------------+
| Payload = DM Message as specified in Section 4.2.1 of RFC 5357|
. Payload = LM Message specified in [I-D.gandhi-ippm-twamp-srpm].
. .
+---------------------------------------------------------------+
Figure 8: Example Probe Response Message for SRv6 Policy
4.2.3. Loopback Measurement Mode
The Loopback measurement mode can be used to measure round-trip delay
for a bidirectional SR Path. The IP header of the probe query
message contains the destination address equals to the sender address
and the source address equals to the reflector address. Optionally,
the probe query message can carry the reverse path information (e.g.
reverse path label stack for SR-MPLS) as part of the SR header. The
probe messages are not punted at the reflector node and it does not
process them and generate response messages. The Sender Control Code
is set to the default value of 0. In this mode, as the probe packet
is not punted on the reflector node for processing, the querier
copies the 'Sequence Number' in 'Session-Sender Sequence Number'
directly. 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 as (t4 - t1).
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4.3. Additional Probe Message Processing Rules
The processing rules defined in this section are applicable to TWAMP
Light messages for delay and loss measurement for Links and end-to-
end SR Paths including SR Policies.
4.3.1. TTL and Hop Limit
The TTL field in the IPv4 and MPLS headers of the probe query
messages is set to 255 [RFC5357]. Similarly, the Hop Limit field in
the IPv6 and SRH headers of the probe query messages is set to 255
[RFC5357].
When using the Destination IPv4 Address from range 127/8, the TTL
field in the IPv4 header is set to 1 [RFC8029]. Similarly, when
using the Destination IPv6 Address from the ::FFFF:127/104 range, the
Hop Limit field in the IPv6 header is set to 1.
For Link performance delay and loss measurements, the TTL or Hop
Limit field in the probe message is set to 1 in both one-way and two-
way measurement modes.
4.3.2. Router Alert Option
The Router Alert IP option (RAO) [RFC2113] is not set in the probe
messages.
4.3.3. UDP Checksum
The UDP Checksum Complement for delay and loss measurement messages
follows the procedure defined in [RFC7820] and can be optionally used
with the procedures defined in this document.
For IPv4 and IPv6 probe messages, where the hardware is not capable
of re-computing the UDP checksum or adding checksum complement
[RFC7820], the sender node sets the UDP checksum to 0 [RFC6936]
[RFC8085]. The receiving node bypasses the checksum validation and
accepts the packets with UDP checksum value 0 for the UDP port being
used for delay and loss measurements.
5. Performance 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] or P2MP Transport
[I-D.shen-spring-p2mp-transport-chain]).
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The procedures for delay and loss measurement described in this
document for P2P SR Policies are also equally applicable to the P2MP
SR Policies. The procedure for one-way measurement is defined as
following:
o The sender root node sends probe query messages using the Tree-SID
defined in [I-D.ietf-pim-sr-p2mp-policy] for the P2MP SR-MPLS
Policy as shown in Figure 9.
o The probe query messages can 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 range
127/8 for IPv4, or the loopback address ::1/128 for IPv6 address.
o Each reflector leaf node sends its IP address in the Source
Address of the probe response messages as shown in Figure 9. This
allows the sender root node to identify the reflector leaf nodes
of the P2MP SR Policy.
o The P2MP root node measures the delay and loss performance for
each P2MP leaf node of the end-to-end P2MP 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tree-SID | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message as shown in Figure 2 for DM or Figure 3 for LM |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: 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 Policy (e.g. for bidirectional SR Path) are outside the scope
of this document.
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6. 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 probe
messages need to be sent to traverse different ECMP paths to measure
performance 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
performance measurement. In IPv4 header of the probe messages,
sweeping of Destination Address from range 127/8 can be used to
exercise particular ECMP paths. As specified in [RFC6437], Flow
Label field in the outer IPv6 header can also be used for sweeping.
The considerations for performance loss measurement for different
ECMP paths of an SR Policy are outside the scope of this document.
7. Performance Delay and Liveness Monitoring
Liveness monitoring is required for connectivity verification and
continuity check in an SR network. The procedure defined in this
document for delay measurement using the TWAMP Light probe messages
can also be applied to liveness monitoring of Links and SR Paths.
The one-way or two-way measurement mode can be used for liveness
monitoring. Liveness failure is notified when consecutive N number
of probe response messages are not received back at the sender node,
where N is locally provisioned value. Note that for one-way and two-
way modes, the failure detection interval and scale for number of
probe messages need to account for the processing of the probe query
messages which need to be punted from the forwarding fast path (to
slow path or control plane) and response messages need to be injected
on the reflector node. This is improved by using the probes in
loopback mode.
8. 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
reflector node.
If desired, attacks can be mitigated by performing basic validation
and sanity checks, at the sender, of the counter or timestamp fields
in received measurement response messages. The minimal state
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associated with these protocols also limits the extent of measurement
disruption that can be caused by a corrupt or invalid message to a
single query/response cycle.
Use of HMAC-SHA-256 in the authenticated mode protects the data
integrity of the probe messages. SRv6 has HMAC protection
authentication defined for SRH [RFC8754]. Hence, probe messages for
SRv6 may not need authentication mode. Cryptographic measures may be
enhanced by the correct configuration of access-control lists and
firewalls.
9. IANA Considerations
This document does not require any IANA action.
10. References
10.1. 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>.
[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>.
[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>.
[I-D.gandhi-ippm-twamp-srpm]
Gandhi, R., Filsfils, C., Voyer, D., Chen, M., and B.
Janssens, "TWAMP Light Extensions for Segment
Routing", draft-gandhi-ippm-twamp-srpm-00 (work
in progress), October 2020.
10.2. Informative References
[IEEE1588]
IEEE, "1588-2008 IEEE Standard for a Precision Clock
Synchronization Protocol for Networked Measurement and
Control Systems", March 2008.
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[RFC2113] Katz, D., "IP Router Alert Option", RFC 2113,
DOI 10.17487/RFC2113, February 1997,
<https://www.rfc-editor.org/info/rfc2113>.
[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>.
[RFC6038] Morton, A. and L. Ciavattone, "Two-Way Active Measurement
Protocol (TWAMP) Reflect Octets and Symmetrical Size
Features", RFC 6038, DOI 10.17487/RFC6038, October 2010,
<https://www.rfc-editor.org/info/rfc6038>.
[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165,
RFC 6335, DOI 10.17487/RFC6335, August 2011,
<https://www.rfc-editor.org/info/rfc6335>.
[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>.
[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>.
[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>.
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[RFC8186] Mirsky, G. and I. Meilik, "Support of the IEEE 1588
Timestamp Format in a Two-Way Active Measurement Protocol
(TWAMP)", RFC 8186, DOI 10.17487/RFC8186, June 2017,
<https://www.rfc-editor.org/info/rfc8186>.
[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>.
[RFC8545] Morton, A., Ed. and G. Mirsky, Ed., "Well-Known Port
Assignments for the One-Way Active Measurement Protocol
(OWAMP) and the Two-Way Active Measurement Protocol
(TWAMP)", RFC 8545, DOI 10.17487/RFC8545, March 2019,
<https://www.rfc-editor.org/info/rfc8545>.
[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>.
[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-08 (work in progress),
July 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-00
(work in progress), July 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-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-00 (work in progress), July
2020.
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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-03 (work in progress),
September 2020.
[I-D.ietf-spring-srv6-network-programming]
Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
Matsushima, S., and Z. Li, "SRv6 Network Programming",
draft-ietf-spring-srv6-network-programming-24 (work in
progress), October 2020.
[BBF.TR-390]
"Performance Measurement from IP Edge to Customer
Equipment using TWAMP Light", BBF TR-390, May 2017.
[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-03 (work in
progress), September 2020.
[I-D.ali-spring-ioam-srv6]
Ali, Z., Gandhi, R., Filsfils, C., Brockners, F., Kumar,
N., Pignataro, C., Li, C., Chen, M., and G. Dawra,
"Segment Routing Header encapsulation for In-situ OAM
Data", draft-ali-spring-ioam-srv6-02 (work in progress),
November 2019.
[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-03 (work
in progress), September 2020.
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 for reviewing this
document and providing useful comments and suggestions. Patrick
Khordoc and Radu Valceanu, both from Cisco Systems have helped
significantly improve the mechanisms defined in this document.
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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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