Simple Two-Way Active Measurement Protocol (STAMP) Extensions for Reflecting STAMP Packet MPLS Extension Headers

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Table of Contents

1. Introduction

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 in the form of TLVs for STAMP. The STAMP test packets are transmitted along a path between a Session-Sender and a Session-Reflector to measure Edge-To-Edge (E2E) performance delay and packet loss along that path.¶

In Situ Operations, Administration, and Maintenance (IOAM) is used for recording and collecting operational and telemetry information while the packet traverses a path between two points in the network. The IOAM data fields are defined in [RFC9197]. Currently, there is no adopted method defined to reflect the collected IOAM data fields back to the Sender, where the Sender can use that information to support the hop-by-hop and edge-to-edge measurement use cases.¶

MPLS packets may carry MPLS Network Action (MNA) Sub-Stacks as defined in [I-D.ietf-mpls-mna-hdr] and Post-Stack Header (PSH) as defined in [I-D.ietf-mpls-mna-ps-hdr].¶

It may be desired to record and collect HBH and E2E operational and telemetry information using active measurement packets between two nodes in a network. This is achieved by augmenting STAMP [RFC8762], using optional STAMP extensions defined in [RFC8972], to reflect MPLS extension headers, including MNA Sub-Stacks and Post-Stack Header, as specified in this document. The procedure defined in this document leverages the existing implementations on the midpoint nodes with MPLS data plane, that supports the MNA Sub-Stacks and Post-Stack Header used, without any additional requirements.¶

2. Conventions Used in This Document

           T1                                       T2
          /                                           \
 +-------+    Test Packet  +-------+                   +-------+
 |       | - - - - - - - - |       | - - - - - - - - ->|       |
 |   S1  |=================|   M1  |===================|   R1  |
 |       |<- - - - - - - - |       | - - - - - - - - - |       |
 +-------+                 +-------+ Reply Test Packet +-------+
          \                                           /
           T4                                       T3

 STAMP Session-Sender                     STAMP Session-Reflector

3. Overview

[RFC8972] defines optional extensions for STAMP. The optional extensions are added to the base STAMP test packet defined in [RFC8762] in the form of TLVs. As specified in [RFC8972], both Session-Sender and Session-Reflector test packets are symmetric in size when including all optional TLVs. The Session-Reflector reflects all received STAMP TLVs from the Session-Sender test packets.¶

As specified in [RFC8762], STAMP test packets are transmitted with IP/UDP headers. Since midpoint nodes do not process the UDP headers in the packets, they are agnostic to the STAMP test packets in the payload.¶

This document also defines a new TLV option for STAMP, called "Reflected MPLS Header MNA Data" (value TBA1). When a STAMP Session-Sender adds an MNA Sub-Stack in the test packet, it also adds a "Reflected MPLS Header MNA Data" STAMP TLV in the Session-Sender test packet with the length set to the MNA Sub-Stack length (NASL) and the value field in the TLV initialized to zeros, in order to receive a copy of that MNA Sub-Stack back in the STAMP TLV. When adding multiple MNA Sub-Stacks in the Session-Sender test packet, corresponding "Reflected MPLS Header MNA Data" STAMP TLVs MUST be added, with the matching length to the MNA Sub-Stack and Ancillary Data and in the same order, in order to receive a copy of that MNA Sub-Stack.¶

Similarly, when a STAMP Session-Sender adds MNA Post-Stack Header in the test packet, it also adds corresponding "Reflected MPLS Header MNA Data" STAMP TLV, with the matching length, in order to receive a copy of that MNA Post-Stack Header.¶

As the procedure defined in this document leverages the existing implementations on the midpoint nodes for the MNA Sub-Stacks and Post-Stack Header, no additional requirements are specified when carrying MNA Sub-Stacks and Post-Stack Header in STAMP. An MNA Sub-Stacks and Post-Stack Header are processed by the nodes using the same procedures specified in the document that defined them.¶

An example STAMP test packet for the MPLS data plane, carrying MNA Sub-Stacks and Post-Stack Header and reflected MNA header data in STAMP TLVs, is shown in Figure 2.¶

 +---------------------------------------------------------------+
 | MPLS Header                                                   |
 ~                                                               ~
 +---------------------------------------------------------------+
 | MNA Sub-Stack-1 I-D.ietf-mpls-mna-hdr                         |
 ~                                                               ~
 +---------------------------------------------------------------+
 ~ ...                                                           ~
 +---------------------------------------------------------------+
 | MNA Sub-Stack-N I-D.ietf-mpls-mna-hdr                         |
 ~                                                               ~
 +---------------------------------------------------------------+
 ~ ...                                                           ~
 +---------------------------------------------------------------+
 | MNA Post-Stack Header I-D.ietf-mpls-mna-ps-hdr                |
 ~                                                               ~
 +---------------------------------------------------------------+
 | IP Header                                                     |
 +---------------------------------------------------------------+
 | UDP Header                                                    |
 +---------------------------------------------------------------+
 | STAMP Packet RFC 8972                                         |
 ~                                                               ~
 +---------------------------------------------------------------+
 | Reflected MPLS Header MNA Data-1 STAMP TLV (TBA1)             |
 ~                                                               ~
 +---------------------------------------------------------------+
 ~ ...                                                           ~
 +---------------------------------------------------------------+
 | Reflected MPLS Header MNA Data-M STAMP TLV (TBA1)             |
 ~                                                               ~
 +---------------------------------------------------------------+
 | Reflected MPLS Header MNA Data STAMP TLV PSH (TBA1)           |
 ~                                                               ~
 +---------------------------------------------------------------+

When the Session-Reflector receives a STAMP test packet with an MNA and a STAMP TLV "Reflected MPLS Header MNA Data," the Session-Reflector that supports this STAMP TLV MUST copy the entire MNA Sub-Stack, including the Ancillary Data and header, into the "Reflected MPLS Header MNA Data" TLV in the Session-Reflector payload. When there are multiple MNA Sub-Stacks in the Session-Sender test packet, each MNA Sub-Stack, including Ancillary Data MUST be processed, in order from the top of the label stack, and copied into the corresponding STAMP TLV, if that STAMP TLV exists. Similarly, the Session-Reflector MUST process MNA Post-Stack Header and copy the entire header and the Ancillary Data into the corresponding STAMP TLV, if that STAMP TLV exists.¶

When the Session-Reflector receives a STAMP test packet with an MNA Sub-Stack or PSH but without corresponding "Reflected MPLS Header MNA Data" STAMP TLV, the Session-Reflector does not copy that MNA Sub-Stack or PSH into the Session-Reflector test packet.¶

When the Session-Sender test packets carry an MNA Sub-Stack or PSH that it does not require the Session-Reflector to reflect in the Session-Reflector test packet, it does not add the matching "Reflected MPLS Header MNA Data" STAMP TLV in the Session-Sender test packet.¶

If the Session-Reflector receives Session-Sender test packets with non-zero values in the first 8 bytes (excluding the Ancillary Data field that may change) of the "Reflected MPLS Header MNA Data" STAMP TLV, it MUST match the values in the corresponding MNA Sub-Stack and PSH in the MPLS header before copying data into the STAMP TLV. This mechanism is employed in case of ambiguity when there are multiple MNA Sub-Stacks and PSH in the MPLS header with the same length present and not all need to be copied and reflected in the STAMP TLVs.¶

The Session-Sender and Session-Reflector test packets are symmetric in size, and hence the Session-Sender and Session-Reflector MUST ensure that the resulting test packets do not exceed the MPLS MTU after adding the Reflected Data STAMP TLVs. If necessary, Reflected Data STAMP TLVs can be removed to avoid violating the MPLS MTU limit.¶

If, for any reason, the Session-Reflector does not use the received "Reflected MPLS Header MNA Data" STAMP TLV for reflecting data, it MUST return the STAMP TLV as unrecognized, i.e., with the U flag (Unrecognized) set in the STAMP TLV Flags using the procedure defined in [RFC8972].¶

The Session-Reflector adds the matching MNA Sub-Stacks and PSH, including Ancillary Data, in the Session-Reflector test packet in the same order for the reverse direction measurements as described in Section 5.2.¶

Note that the use case where the MNA Sub-Stack and PSH length changes in the Session-Sender test packets along the path is outside the scope of this document. Also, the use case where MNA Sub-Stacks and PSH are added or removed in the Session-Sender test packets along the path is outside the scope of this document.¶

4. Use Case of Reflecting IOAM Data Fields

In Situ Operations, Administration, and Maintenance (IOAM) is used for recording and collecting operational and telemetry information while the packet traverses a path between two points in the network. The IOAM data fields are defined in [RFC9197]. Examples of data recorded by IOAM Trace Options include per-hop information, such as node ID, timestamp, queue depth, interface ID, interface load, etc. The information collected can be used for monitoring ECMP paths, proof-of-transit, and troubleshooting failures in the network. IOAM can be used with STAMP test packets for active measurement. The procedure and STAMP extensions defined in this document can be used to reflect the collected IOAM data fields back to the Sender, where the Sender can use that information to support the hop-by-hop and edge-to-edge measurement use cases.¶

[I-D.ietf-mpls-mna-ioam] defines extensions using MNA to carry IOAM data that may be carried in MNA Sub-Stack [I-D.ietf-mpls-mna-hdr] or in MNA Post-Stack Header [I-D.ietf-mpls-mna-ps-hdr]. The STAMP Session-Sender and Session-Reflector test packets can carry an MNA Sub-Stack and PSH for HBH and E2E operational and telemetry information for active measurement, as shown in Figure 3, as an example.¶

 +---------------------------------------------------------------+
 | MPLS Header                                                   |
 +---------------------------------------------------------------+
 | IOAM MNA Sub-Stack I-D.ietf-mpls-mna-ioam                     |
 ~                                                               ~
 +---------------------------------------------------------------+
 | IOAM MNA PSH I-D.ietf-mpls-mna-ioam                           |
 ~                                                               ~
 +---------------------------------------------------------------+
 | IP Header                                                     |
 +---------------------------------------------------------------+
 | UDP Header                                                    |
 +---------------------------------------------------------------+
 | STAMP Packet RFC 8972                                         |
 +---------------------------------------------------------------+
 | Reflected MPLS Header MNA Data STAMP TLV (TBA1)               |
 ~                                                               ~
 +---------------------------------------------------------------+
 | Reflected MPLS Header MNA Data STAMP TLV PSH (TBA1)           |
 ~                                                               ~
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

5. STAMP Extensions

  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |STAMP TLV Flags|  Type=TBA1    |         Length                |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                  Reflected MPLS Header MNA Data               |
 ~                                                               ~
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

6. Security Considerations

The security considerations specified in [RFC8762], [RFC8972], [I-D.ietf-mpls-mna-hdr] and [I-D.ietf-mpls-mna-ps-hdr] apply to the procedure and extensions defined in this document. In addition, the security considerations specified in [RFC9197] and [I-D.ietf-mpls-mna-ioam] also apply when using the IOAM.¶

7. IANA Considerations

IANA has created the "STAMP TLV Types" registry for [RFC8972]. IANA is requested to allocate a value for the "Reflected MPLS Header MNA Data" TLV Type from the IETF Review TLV range of the same registry.¶

IANA is requested to allocate a value for the Sub-TLV Type "MNA Header Control" (Type TBA2) for the STAMP TLV Type "Reflected Test Packet Control TLV" (Type TBA-ASYM) defined in [I-D.ietf-ippm-asymmetrical-pkts], from the "STAMP Sub-TLV Types" registry.¶

Acknowledgments

TBA¶

Authors' Addresses