Performance Measurement Using TWAMP Light for Segment Routing Networks
draft-gandhi-spring-twamp-srpm-02
The information below is for an old version of the document.
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|---|---|---|---|
| Authors | Rakesh Gandhi , Clarence Filsfils , Daniel Voyer , Mach Chen , Bart Janssens | ||
| Last updated | 2019-08-30 (Latest revision 2019-05-15) | ||
| Replaced by | draft-gandhi-spring-stamp-srpm | ||
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draft-gandhi-spring-twamp-srpm-02
SPRING Working Group R. Gandhi, Ed.
Internet-Draft C. Filsfils
Intended Status: Standards Track Cisco Systems, Inc.
Expires: March 2, 2020 D. Voyer
Bell Canada
M. Chen
Huawei
B. Janssens
Colt
August 30, 2019
Performance Measurement Using TWAMP Light
for Segment Routing Networks
draft-gandhi-spring-twamp-srpm-02
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 synthetic 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) for Delay Measurement, and also
uses the mechanisms defined in this document for Loss Measurement.
The procedure specified is applicable to SR-MPLS and SRv6 data planes
and are used for both links and end-to-end 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 http://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."
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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 . . . . . . . . . . . . . . 4
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 4
2.3. Reference Topology . . . . . . . . . . . . . . . . . . . . 5
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Example Provisioning Model for TWAMP Light . . . . . . . . 6
3.2. STAMP Applicability . . . . . . . . . . . . . . . . . . . 6
4. Probe Messages . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Probe Query Message . . . . . . . . . . . . . . . . . . . 7
4.1.1. Delay Measurement Probe Query Message . . . . . . . . 7
4.1.1.1. Delay Measurement Authentication Mode . . . . . . 8
4.1.2. Loss Measurement Probe Query Message . . . . . . . . . 8
4.1.2.1. Loss Measurement Authentication Mode . . . . . . . 11
4.1.3. Probe Query for SR Links . . . . . . . . . . . . . . . 11
4.1.4. Probe Query for End-to-end Measurement for SR Policy . 12
4.1.4.1. Probe Query Message for SR-MPLS Policy . . . . . . 12
4.1.4.2. Probe Query Message for SRv6 Policy . . . . . . . 12
4.2. Probe Response Message . . . . . . . . . . . . . . . . . . 13
4.2.1. One-way Measurement Mode . . . . . . . . . . . . . . . 15
4.2.2. Two-way Measurement Mode . . . . . . . . . . . . . . . 16
4.2.2.1. Return Path TLV . . . . . . . . . . . . . . . . . 16
4.2.2.2. Probe Response Message for SR-MPLS Policy . . . . 17
4.2.2.3. Probe Response Message for SRv6 Policy . . . . . . 18
4.2.3. Loopback Measurement Mode . . . . . . . . . . . . . . 18
5. Performance Measurement for P2MP SR Policies . . . . . . . . . 18
6. ECMP Support for SR Policies . . . . . . . . . . . . . . . . . 19
7. Additional Message Processing Rules . . . . . . . . . . . . . 20
7.1. TTL Value . . . . . . . . . . . . . . . . . . . . . . . . 20
7.2. Router Alert Option . . . . . . . . . . . . . . . . . . . 20
7.3. UDP Checksum . . . . . . . . . . . . . . . . . . . . . . . 20
8. Security Considerations . . . . . . . . . . . . . . . . . . . 20
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9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 21
10.1. Normative References . . . . . . . . . . . . . . . . . . 21
10.2. Informative References . . . . . . . . . . . . . . . . . 22
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24
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.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 synthetic probe messages. These
protocols rely on control-channel signaling to establish a
test-channel over an UDP path. These protocols lack support for
direct-mode Loss Measurement (LM) to detect actual data traffic loss
which is required in SR networks. The Simple Two-way Active
Measurement Protocol (STAMP) [I-D.ippm-stamp] alleviates the
control-channel signaling by using configuration data model to
provision a test-channel. 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 control-channel signaling.
This document specifies procedures for sending and processing
synthetic probe query and response messages for Performance
Measurement in SR networks. The procedure uses the mechanisms
defined in [RFC5357] (TWAMP Light) for Delay Measurement (DM), and
also uses the mechanisms defined in this document for Loss
Measurement. The procedure specified is applicable to SR-MPLS and
SRv6 data planes and are used for both links and end-to-end SR
Policies. This document also defines mechanisms for handling ECMPs
of SR Policies for performance delay measurements.
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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.
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.
SR-MPLS: Segment Routing with MPLS data plane.
SRv6: Segment Routing with IPv6 data plane.
STAMP: Simple Two-way Active Measurement Protocol.
TC: Traffic Class.
TWAMP: Two-Way Active Measurement Protocol.
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2.3. Reference Topology
In the reference topology shown below, the sender node R1 initiates a
probe query for performance measurement and the responder node R5
sends a probe response for the query message received. The probe
response is sent to the sender node R1. The nodes R1 and R5 may be
directly connected via a link enabled with Segment Routing or there
exists a Point-to-Point (P2P) SR Policy
[I-D.spring-segment-routing-policy] on node R1 with destination to
node R5. In case of Point-to-Multipoint (P2MP), SR Policy
originating from source node R1 may terminate on multiple destination
leaf nodes [I-D.spring-sr-p2mp-policy].
+-------+ Query +-------+
| | - - - - - - - - - ->| |
| R1 |---------------------| R5 |
| |<- - - - - - - - - - | |
+-------+ Response +-------+
Sender Responder
Reference Topology
3. Overview
For one-way, two-way and round-trip delay measurements in Segment
Routing networks, the TWAMP Light procedures defined in Appendix I of
[RFC5357] are used. For one-way and two-way direct-mode and
inferred-mode loss measurements in Segment Routing networks, the
procedures defined in this document are used. One-way loss
measurement provides receive packet loss whereas two-way loss
measurement provides both transmit and receive packet loss. Separate
UDP destination port numbers are user-configured for delay and loss
measurements from the range specified in [I-D.ippm-stamp]. For both
links and end-to-end SR Policies, no PM session for delay or loss
measurement is created on the responder node R5 [RFC5357].
For Performance Measurement, synthetic 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 Policies.
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
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collect the receive traffic counters for the incoming link or
incoming SID where the probe query messages are received at the
responder node (incoming link or incoming SID needed since the
responder node does not have PM session state present).
The In-Situ Operations, Administration, and Maintenance (IOAM)
mechanisms for SR-MPLS defined in [I-D.spring-ioam-sr-mpls] and for
SRv6 defined in [I-D.spring-srv6-oam] 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 for TWAMP Light
An example of a provisioning model and typical measurement parameters
for performance delay and loss measurements using TWAMP Light is
shown in the following Figure:
+------------+
| Controller |
+------------+
Measurement Protocol / \ Measurement Protocol
Destination UDP Port / \ Destination UDP port
Measurement Type / \ Measurement Type
Delay/Loss / \ Delay/Loss
Authentication Mode & Key / \ Authentication Mode & Key
Timestamp Format / \
Measurement Mode / \
Padding/MBZ Bytes / \
Loss Measurement Mode / \
v v
+-------+ +-------+
| | | |
| R1 |------------| R5 |
| | | |
+-------+ +-------+
Sender Responder
Provisioning Model
The mechanisms used to provision the sender and responder nodes are
outside the scope of this document.
3.2. STAMP Applicability
The Simple Two-way Active Measurement Protocol (STAMP)
[I-D.ippm-stamp] and the STAMP TLVs [I-D.ippm-stamp-option-tlv] are
both equally applicable to the procedures specified in this document.
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This is because the delay measurement message formats defined for
STAMP and STAMP TLVs are backwards compatible with the delay
measurement message formats defined in [RFC5357]. Hence, the same
user-configured destination UDP port for delay measurement can be
used for STAMP and TWAMP Light messages. The STAMP with a TLV for
"direct measurement" can be used for combined delay + loss
measurement using a separate user-configured UDP destination port.
The loss measurement probe and query messages defined in this
document are also equally applicable to STAMP and STAMP TLVs, by
using the packet padding size of 30 octets.
4. Probe Messages
4.1. Probe Query Message
In this document, the probe messages defined in [RFC5357] are used
for Delay and Loss measurements for SR links and end-to-end SR
Policies. The user-configured destination UDP ports (separate UDP
ports for delay and loss message formats) are used for identifying
the PM probe packets as described in Appendix I of [RFC5357]. The
sender uses the UDP port number following the guidelines specified in
Section 6 in [RFC6335].
4.1.1. Delay Measurement Probe Query Message
The message content for Delay Measurement probe query message using
UDP header [RFC768] is shown in Figure 1. 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 query and
response. The DM probe query message contains the payload for delay
measurement defined in Section 4.1.2 of [RFC5357]. For symmetrical
size query and response messages [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 = Responder IPv4 or IPv6 Address .
. Protocol = UDP .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Sender .
. Destination Port = User-configured Port for Delay Measurement.
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. .
+---------------------------------------------------------------+
| Payload = Message as specified in Section 4.2.1 of RFC 5357 | |
| Payload = Message as specified in Section 4.1.2 of RFC 5357 |
. .
+---------------------------------------------------------------+
Figure 1: DM Probe Query Message
Timestamp field is eight bytes. It is recommended to use the IEEE
1588v2 Precision Time Protocol (PTP) truncated 64-bit timestamp
format [IEEE1588] as specified in [RFC8186].
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 responder 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 Probe Query Message
In this document, new probe query message formats are defined for
loss measurement as shown in Figure 3A and Figure 3B. The message
formats are hardware efficient due to the small size payload and
well-known locations of counters. They are similar to the delay
measurement message formats and do not require any backwards
compatibility and support for the existing DM message formats from
[RFC5357].
The message content for Loss Measurement probe query message using
UDP header [RFC768] is shown in Figure 2. The LM probe query message
is sent with user-configured Destination UDP port number for LM.
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 query and response. The LM probe query
message contains the payload for loss measurement as defined in
Figure 3A and Figure 3B. For symmetrical size query and response
messages [RFC6038], the LM probe query message contains the payload
format defined in Figure 7A and Figure 7B for loss measurement.
+---------------------------------------------------------------+
| IP Header |
. Source IP Address = Sender IPv4 or IPv6 Address .
. Destination IP Address = Responder IPv4 or IPv6 Address .
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. Protocol = UDP .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Sender .
. Destination Port = User-configured Port for Loss Measurement .
. .
+---------------------------------------------------------------+
| Payload = Message as specified in Figure 3A or 3B | |
| Payload = Message as specified in Figure 7A or 7B |
. .
+---------------------------------------------------------------+
Figure 2: DM Probe Query Message
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transmit Counter |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X|B| Reserved | Block Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Packet Padding .
. .
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Checksum Complement |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3A: LM Probe Query Message
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (12 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transmit Counter |
| |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X|B|I| Reserved | Block Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (6 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HMAC (16 octets) |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Packet Padding .
. .
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Checksum Complement |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3B: LM Probe Query Message - Authenticated Mode
Sequence Number (32-bit): As defined in [RFC5357].
Transmit Counter (64-bit): The number of packets sent by the sender
node in the query message and by the responder node in the response
message. The counter is always written at the fixed location in the
probe query and response messages.
Receive Counter (64-bit): The number of packets received at the
responder node. It is written by the responder node in the probe
response message.
Sender Counter (64-bit): This is the exact copy of the transmit
counter from the received query message. It is written by the
responder node in the probe response message.
Sender Sequence Number (32-bit): As defined in [RFC5357].
Sender TTL: As defined in [RFC5357].
Flag: The meanings of the Flag bits are:
X: Extended counter format indicator. Indicates the use of
extended (64-bit) counter values. Initialized to 1 upon creation
(and prior to transmission) of an LM Query and copied from an LM
Query to an LM response. Set to 0 when the LM message is
transmitted or received over an interface that writes 32-bit
counter values.
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B: Octet (byte) count. When set to 1, indicates that the Counter
1-4 fields represent octet counts. The octet count applies to all
packets within the LM scope, and the octet count of a packet sent
or received includes the total length of that packet (but excludes
headers, labels, or framing of the channel itself). When set to
0, indicates that the Counter fields represent packet counts.
I: Inferred Mode Loss Measurement: When set to 1, indicates that
inferred-mode of loss measurement is used. When set to 0, it
indicates direct-mode of loss measurement is used.
Block Number (16-bit): The Loss Measurement using Alternate-Marking
method defined in [RFC8321] requires to identify the Block Number (or
color) of the traffic counters. The probe query and response
messages carry Block Number for the traffic counters for loss
measurement. In both probe query and response messages, the counters
MUST belong to the same Block Number.
HMAC: The PM probe packet in authenticated mode includes a key Hashed
Message Authentication Code (HMAC) ([RFC2104]) hash. Each probe
query and response messages are authenticated by adding Sequence
Number with Hashed Message Authentication Code (HMAC) TLV. It can
use HMAC-SHA-256 truncated to 128 bits (similarly to the use of it in
IPSec defined in [RFC4868]); hence the length of the HMAC field is 16
octets.
HMAC uses its own key and the mechanism to distribute the HMAC key is
outside the scope of this document.
In authenticated mode, only the sequence number is encrypted, and the
other payload fields are sent in clear text. The probe packet MAY
include Comp.MBZ (Must Be Zero) variable length field to align the
packet on 16 octets boundary.
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 responder nodes. A separate user-configured
destination UDP port is used for the loss measurement in
authentication mode due to the different message format.
4.1.3. Probe Query for SR Links
The probe query message as defined in Figure 1 is sent on the
congruent path of the data traffic for Delay measurement. The probe
query message as defined in Figure 2 is sent on the congruent path of
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the data traffic for Loss measurement.
4.1.4. Probe Query for End-to-end Measurement for SR Policy
The performance delay and loss measurement for segment routing is
applicable to both SR-MPLS and SRv6 Policies.
4.1.4.1. Probe Query Message for SR-MPLS Policy
The probe query messages for end-to-end performance measurement of an
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 List(1) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment List(n) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSID | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message as shown in Figure 1 for DM or Figure 2 for LM |
. .
+---------------------------------------------------------------+
Figure 4: Probe Query Message for SR-MPLS Policy
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.spring-mpls-path-segment] of
the SR-MPLS Policy is used for accounting received traffic on the
egress node for loss measurement. The PSID is not added for
end-to-end SR Policy delay 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 [I-D.6man-segment-routing-header]. The
probe query messages for end-to-end performance measurement of an
SRv6 Policy is sent using its SRv6 Segment Routing Header (SRH) and
Segment List as shown in Figure 5.
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+---------------------------------------------------------------+
| SRH |
. END.OTP (DM) or END.OP (LM) with Target SRv6 SID .
. .
+---------------------------------------------------------------+
| Message as shown in Figure 1 for DM or Figure 2 for LM |
. (Using IPv6 Source and Destination Addresses) .
. .
+---------------------------------------------------------------+
Figure 5: Probe Query Message for SRv6 Policy
For delay measurement of SRv6 Policy using SRH, END function END.OTP
[I-D.spring-srv6-oam] is used with the target SRv6 SID to punt probe
messages on the target node, as shown in Figure 5. Similarly, for
loss measurement of SRv6 Policy, END function END.OP
[I-D.spring-srv6-oam] is used with target SRv6 SID to punt probe
messages on the target node.
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 = Responder IPv4 or IPv6 Address .
. Destination IP Address = Source IP Address from Query .
. Protocol = UDP .
. .
+---------------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Responder .
. Destination Port = Source Port from Query .
. .
+---------------------------------------------------------------+
| DM Payload as specified in Section 4.2.1 of RFC 5357, or |
. LM Payload as specified in Figure 7A or 7B in this document .
. .
+---------------------------------------------------------------+
Figure 6: Probe Response Message
In this document, new probe response message formats are defined for
loss measurement as shown in Figure 7A and Figure 7B. The message
formats are hardware efficient due to the small size payload and well
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known locations of the counters. They are also similar to the delay
measurement message formats.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transmit Counter |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X|B| Reserved | Block Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receive Counter |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Counter |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X|B| Reserved | Sender Block Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender TTL | |
+-+-+-+-+-+-+-+-+ +
| Packet Padding |
. .
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Checksum Complement |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7A: LM Probe Response Message
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (12 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transmit Counter |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X|B| Reserved | Block Number |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (6 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receive Counter |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (8 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (12 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Counter |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X|B| Reserved | Sender Block Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender TTL | |
+-+-+-+-+-+-+-+-+ +
| MBZ (15 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HMAC (16 octets) |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Packet Padding .
. .
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Checksum Complement |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7B: LM Probe Response Message - Authenticated Mode
4.2.1. One-way Measurement Mode
In one-way performance measurement mode, the probe response message
as defined in Figure 6 is sent back out of band to the sender node,
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for both SR links and SR Policies.
4.2.2. Two-way Measurement Mode
In two-way performance measurement mode, when using a bidirectional
path, the probe response message as defined in Figure 6 is sent back
on the congruent path of the data traffic to the sender node, for
both SR links and SR Policies.
4.2.2.1. Return Path TLV
For two-way performance measurement, the responder node needs to send
the probe response message on a specific reverse path. This way the
destination node does not require any additional state. The sender
node can request in the probe query message to the responder node to
send a response back on a given reverse path (e.g. co-routed path for
two-way measurement).
[I-D.ippm-stamp-option-tlv] defines STAMP probe query messages that
can include one or more optional TLVs. New TLV Type (TBA1) is
defined in this document for Return Path to carry reverse path for
probe response messages (in the payload of the message). The format
of the Return Path TLV is shown in Figure 8A and Figure 8B:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = TBA1 | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Return Path Sub-TLVs |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8A: Return Path TLV
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment List(1) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Segment List(n) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8B: Segment List Sub-TLV in Return Path TLV
The Segment List Sub-TLV in the Return Path TLV can be one of the
following Types:
o Type (value 1): Respond back on Incoming Interface (Layer-3 and
Layer-2) (Segment List is Empty)
o Type (value 2): SR-MPLS Segment List (Label Stack) of the Reverse
SR Path
o Type (value 3): SR-MPLS Binding SID [I-D.pce-binding-label-sid] of
the Reverse SR Policy
o Type (value 4): SRv6 Segment List of the Reverse SR Path
o Type (value 5): SRv6 Binding SID [I-D.pce-binding-label-sid] of
the Reverse SR Policy
The Return Path TLV is optional. The PM sender node MUST only insert
one Return Path TLV in the probe query message and the responder node
MUST only process the first Return Path TLV in the probe query
message and ignore other Return Path TLVs if present. The responder
node MUST send probe response message back on the reverse path
specified in the Return Path TLV and MUST NOT add Return Path TLV in
the probe response message.
4.2.2.2. Probe Response Message for SR-MPLS Policy
The message content for sending probe response message for two-way
end-to-end performance measurement of an SR-MPLS Policy is shown in
Figure 9.
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 List(1) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment List(n) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message as shown in Figure 6 |
. .
+---------------------------------------------------------------+
Figure 9: Probe Response Message for SR-MPLS Policy
The Path Segment Identifier (PSID) [I-D.spring-mpls-path-segment] of
the forward SR Policy can be used to find the reverse SR Policy to
send the probe response message for two-way measurement of SR Policy.
4.2.2.3. 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 end-to-end performance
measurement of an SRv6 Policy with SRH is shown in Figure 10.
+---------------------------------------------------------------+
| SRH |
. END.OTP (DM) or END.OP (LM) with Target SRv6 SID .
. .
+---------------------------------------------------------------+
| Message as shown in Figure 6 |
. (with IPv6 Source and Destination Addresses) .
. .
+---------------------------------------------------------------+
Figure 10: 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 responder 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
responder node does not process the PM probe messages and generate
response messages.
5. Performance Measurement for P2MP SR Policies
The procedures for delay and loss measurement described in this
document for Point-to-Point (P2P) SR Policies
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[I-D.spring-segment-routing-policy] are also equally applicable to
the Point-to-Multipoint (P2MP) SR Policies
[I-D.spring-sr-p2mp-policy] as following:
o The sender root node sends probe query messages using either Spray
P2MP segment or TreeSID P2MP segment defined in
[I-D.spring-sr-p2mp-policy] over the P2MP SR Policy.
o The sender root node sets the PM probe query message Destination
IPv4 Address from the 127/8 range for SR-MPLS Policy.
o Each responder leaf node sends its IP address in the Source
Address of the probe response messages. This allows the sender
root node to identify the responder leaf nodes of the P2MP SR
Policy.
o The P2MP root node measures the end-to-end delay and loss
performance for each P2MP leaf node.
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 PM 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. Following mechanisms can be used in
PM probe messages to take advantage of the hashing function in
forwarding plane to influence the path taken by them.
o The mechanisms described in [RFC8029] and [RFC5884] for handling
ECMPs are also applicable to the performance measurement. In the
IP/UDP header of the PM probe messages, Destination Addresses in
127/8 range for IPv4 or 0:0:0:0:0:FFFF:7F00/104 range for IPv6 can
be used to exercise a particular ECMP path. As specified in
[RFC6437], 3-tuple of Flow Label, Source Address and Destination
Address fields in the IPv6 header can also be used.
o For SR-MPLS Policy, entropy label [RFC6790] can be used in the PM
probe messages.
o For SRv6 Policy using SRH, Flow Label in the SRH
[I-D.6man-segment-routing-header] of the PM probe messages can be
used, in addition to the Source and Destination Addresses of the
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SRv6 Policy.
7. Additional Message Processing Rules
7.1. TTL Value
The TTL or the Hop Limit field in the IP, MPLS and SRH headers of the
probe query messages are set to 255 [RFC5357].
When using the Destination IPv4 Address from the 127/8 range, the TTL
in the IPv4 header is set to 1 [RFC8029]. Similarly, when using the
Destination IPv6 Address from the 0:0:0:0:0:FFFF:7F00/104 range, the
Hop Limit field in the inner IPv6 header is set to 1 whereas in the
outer IPv6 header is set to 255.
7.2. Router Alert Option
The Router Alert IP option is not set when using the routable
Destination IP Address in the probe messages.
When using the Destination IPv4 Address from the 127/8 range, the
Router Alert IP Option of value 0x0 [RFC2113] for IPv4 is set in the
IP header [RFC8029]. Similarly, when using the Destination IPv6
Address from the 0:0:0:0:0:FFFF:7F00/104 range, the Router Alert IP
Option of value 69 [RFC7506] for IPv6 is set in the IP header.
7.3. UDP Checksum
The 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 of 0 for the UDP port being
used for PM.
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 responder node.
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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
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 [I-D.6man-segment-routing-header].
Hence, PM 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
IANA is requested to allocate value for the following Return Path TLV
Type for [I-D.ippm-stamp-option-tlv] to be carried in PM probe query
messages:
o Type TBA1: Return Path TLV
10. References
10.1. Normative References
[RFC768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, September 2006.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, October 2008.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", RFC 8174, May 2017.
[I-D.spring-srv6-oam] Ali, Z., et al., "Operations, Administration,
and Maintenance (OAM) in Segment Routing Networks with
IPv6 Data plane (SRv6)", draft-ali-spring-srv6-oam, work
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in progress.
[I-D.ippm-stamp] Mirsky, G. et al. "Simple Two-way Active
Measurement Protocol", draft-ietf-ippm-stamp, work in
progress.
[I-D.ippm-stamp-option-tlv] Mirsky, G., et al., "Simple Two-way
Active Measurement Protocol Optional Extensions",
draft-ietf-ippm-stamp-option-tlv, work in progress.
10.2. Informative References
[IEEE1588] IEEE, "1588-2008 IEEE Standard for a Precision Clock
Synchronization Protocol for Networked Measurement and
Control Systems", March 2008.
[RFC2104] Krawczyk, H., Bell-are, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104, February
1997.
[RFC2113] Katz, D., "IP Router Alert Option", RFC 2113, February
1997.
[RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-
384, and HMAC-SHA-512 with IPsec", RFC 4868, May 2007.
[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.
[RFC6038] Morton, A. and L. Ciavattone, "Two-Way Active Measurement
Protocol (TWAMP) Reflect Octets and Symmetrical Size
Features", RFC 6038, October, 2010
[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, August 2011.
[RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme,
"IPv6 Flow Label Specification", RFC 6437, November 2011.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, November 2012.
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[RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement
for the Use of IPv6 UDP Datagrams with Zero Checksums",
RFC 6936, April 2013.
[RFC7506] Raza, K., Akiya, N., and C. Pignataro, "IPv6 Router Alert
Option for MPLS Operations, Administration, and
Maintenance (OAM)", RFC 7506, DOI 10.17487/RFC7506, April
2015, <http://www.rfc-editor.org/info/rfc7506>.
[RFC7820] Mizrahi, T., "UDP Checksum Complement in the One-Way
Active Measurement Protocol (OWAMP) and Two-Way Active
Measurement Protocol (TWAMP)", RFC 7820, March 2016.
[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Kumar, N.,
Aldrin, S. and M. Chen, "Detecting Multiprotocol Label
Switched (MPLS) Data-Plane Failures", RFC 8029, March
2017.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <http://www.rfc-editor.org/info/rfc8085>.
[RFC8186] Mirsky, G., and I. Meilik, "Support of the IEEE 1588
Timestamp Format in a Two-Way Active Measurement Protocol
(TWAMP)", RFC 8186, June 2017.
[RFC8321] Fioccola, G. Ed., "Alternate-Marking Method for Passive
and Hybrid Performance Monitoring", RFC 8321, January
2018.
[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>.
[I-D.spring-segment-routing-policy] Filsfils, C., et al., "Segment
Routing Policy Architecture",
draft-ietf-spring-segment-routing-policy, work in
progress.
[I-D.spring-sr-p2mp-policy] Voyer, D. Ed., et al., "SR Replication
Policy for P2MP Service Delivery",
draft-voyer-spring-sr-p2mp-policy, work in progress.
[I-D.spring-mpls-path-segment] Cheng, W., et al., "Path Segment in
MPLS Based Segment Routing Network",
draft-ietf-spring-mpls-path-segment, work in progress.
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[I-D.6man-segment-routing-header] Filsfils, C., et al., "IPv6
Segment Routing Header (SRH)",
draft-ietf-6man-segment-routing-header, work in progress.
[I-D.pce-binding-label-sid] Filsfils, C., et al., "Carrying Binding
Label Segment-ID in PCE-based Networks",
draft-sivabalan-pce-binding-label-sid, work in progress.
[BBF.TR-390] "Performance Measurement from IP Edge to Customer
Equipment using TWAMP Light", BBF TR-390, May 2017.
[I-D.spring-ioam-sr-mpls] Gandhi, R. Ed., et al., "Segment Routing
with MPLS Data Plane Encapsulation for In-situ OAM Data",
draft-gandhi-spring-ioam-sr-mpls, work in progress.
Acknowledgments
The authors would like to thank Thierry Couture for various
discussions on the use-cases for TWAMP Light 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. The
authors would like to acknowledge the earlier work on the loss
measurement using TWAMP described in
draft-xiao-ippm-twamp-ext-direct-loss.
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
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Huawei
Email: mach.chen@huawei.com
Bart Janssens
Colt
Email: Bart.Janssens@colt.net
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