Internet-Draft Asymmetrical Packets in STAMP October 2023
Mirsky, et al. Expires 22 April 2024 [Page]
Workgroup:
Network Working Group
Internet-Draft:
draft-mirsky-ippm-asymmetrical-pkts-02
Published:
Intended Status:
Standards Track
Expires:
Authors:
G. Mirsky
Ericsson
E. Ruffini
OutSys
H. Nydell
Accedian Networks

Performance Measurement with Asymmetrical Packets in STAMP

Abstract

This document describes an optional extension to a Simple Two-way Active Measurement Protocol (STAMP) that enables the use of STAMP test and reflected packets of variable length during a single STAMP test session. In some use cases, the use of asymmetrical test packets allow for the creation of more realistic flows of test packets and, thus, a closer approximation between active performance measurements and conditions experienced by the monitored application.

Also, the document includes an analysis of challenges related to performance monitoring in a multicast network. It defines procedures and STAMP extensions to achieve more efficient measurements with a lesser impact on a network.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on 22 April 2024.

Table of Contents

1. Introduction

Simple Two-way Active Measurement Protocol (STAMP) [RFC8762] defined the STAMP base functionalities and, among them, the use of symmetrical test packets. In some scenarios, e.g., rate measurements discussed in [RFC7497], it is beneficial not only to use a variable size of the test packets transmitted downstream while controlling length, number, and interpacket interval for reflected test packets. This document specifies an optional extension of STAMP as defined in [RFC8972] that allows for control of the length, number, and interpacket interval of reflected STAMP test packets transmitted in response to a received STAMP test packet.

Measurement of performance metrics in a multicast network using an active measurement method has specific challenges compared to what operators experience monitoring in a unicast network. This document analyzes these challenges, and defines procedures and STAMP extensions to achieve more efficient measurements with a lesser impact on a network.

1.1. Terminology

STAMP Simple Two-way Active Measurement Protocol

1.2. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

2. Problem Statement

STAMP ([RFC8762]) allows for variable lengths of the test packets transmitted by a Session-Sender. [RFC7497] analyses rate measurement scenarios where it is beneficial to enable control of the responding node reflecting the received test packet with a different length and, in some cases, with a series of equally timed test packets.

Measuring performance metrics using an active method in a multicast network is another use case where the ability to control the behavior of the Session-Reflector is beneficial. In some environments, an operator may request that reflected packets be as small as the protocol allows. In another scenario, an operator may request the suppression of test packet reflection altogether. Another scenario may need the ability to define a subset of nodes processing received test packets.

3. Reflected Test Packet Control TLV

This document defines a new optional STAMP extension, Reflected Test Packet Control TLV. The format of the Reflected Test Packet Control TLV is presented in Figure 1.

  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     |           Length              |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                  Length of the Reflected Packet               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                 Number of the Reflected Packets               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |             Interval Between the Reflected Packets            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ~                            Sub-TLVs                           ~
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Reflected Test Packet Control TLV Format

The interpretation of the fields is as follows:

A Session-Sender MAY include the Reflected Test Packet Control TLV in a STAMP test packet. If the received STAMP test packet includes the Reflected Test Packet Control TLV, the Session-Reflector MUST transmit a sequence of reflected test packets according to the following rules:

3.1. Address Group Sub-TLVs

3.1.1. Layer 2 Address Group Sub-TLV

Layer 2 Address Group sub-TLV: A 16-octet sub-TLV that includes the EUI-48 Address Group Mask and EUI-48 Address Group. The Type value is TBA2 (Section 7.2). The value of the Length field MUST be equal to 12. The format of Layer 2 Address Group sub-TLV is presented in Figure 2.

 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                     EUI-48 Address Group Mask                 |
+                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                               |                               |
|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|                               |
|                       EUI-48 Address Group                    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Layer 2 Address Group Sub-TLV Format

The Value field consists of the following fields:

  • EUI-48 Address Group Mask: A six-octet field that represents the bitmask to be applied to the Session-Reflector MAC Address.
  • EUI-48 Address Group: A six-octet field that represents the group this TLV is addressed to. If the Session-Reflector applies EUI-48 Address Group Mask to its MAC Address and the result is different from EUI-48 Address Group, then the Session-Reflector MUST stop processing the received test packet.

3.1.2. Layer 3 Address Group Sub-TLV

Layer 3 Address Group sub-TLV: A variable-length sub-TLV that includes the IP Address Family, IP Network Prefix, and IP Prefix Length. The Type value is TBA3 (Section 7.2). The value of the Length field MUST be equal to 8 or 20. The format of Layer 3 Address Group sub-TLV is presented in Figure 3.

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Family| Prefix Length |           Reserved            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~                       IP Network Prefix                       ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Layer 3 Address Group Sub-TLV Format

The Value field consists of the following fields:

  • Address Family: A one-octet field that indicates the type of IP address contained in the IP Network Prefix field. If that is IPv4 address, then the value MUST be set to 1. For the IPv6 address, the value MUST be set to 2. Other values MUST be considered invalid.
  • Prefix Length: A one-octet unsigned integer field that contains the length, in bits, of the network prefix part of the value in the IP Network field.
  • Reserved: A two-octet field. The field MUST be zeroed on transmission and ignored on receipt.
  • IP Network Prefix: A variable-length field. Depending on the value of the Address Family field, the field contains either IPv4, or IPv6 address. If the former, the length is four octets; if the latter - 16 octets.

4. Theory of Operation

4.1. Rate Measurement

[RFC7497] defines the problem of access rate measurement in access networks. Essential requirements identified for a test protocol are the ability to control packet characteristics on the tested path, such as asymmetric rate and asymmetric packet size. The Reflected Test Packet Control TLV, defined in Section 3, conforms to the requirements for measuring access rate by providing optional controls of the number of reflected test packets, the size of the reflected packet(s), and the time interval, i.e., rate, in transmitting the sequence of the reflected test packets.

4.2. Active Performance Measurement in Multicast Environment

According to [RFC8972], a STAMP Session is demultiplexed by a Session-Reflector by the tuple that consists of source and destination IP addresses, source and destination UDP port numbers, or the source IP address and STAMP Session Identifier. That is also the case of the monitoring performance of a multicast flow, despite that the destination IP address is multicast. Therefore the behavior of a Session-Reflector upon receiving a STAMP test packet over a multicast tree is as defined in [RFC8762] and [RFC8972]. The Session-Reflector MUST use the source IP address of the received STAMP test packet as the destination IP address of the reflected test packet, and MUST use one of the IP addresses associated with the node as the source IP address for that packet.

The Session-Sender has to pay more attention when sending a multicast STAMP packet. Instead of possibly, receiving a reply from a Session-Reflector may now receive multiple replies from multiple counterparts: its STAMP Session has a 1:N relation. Network traffic is another aspect that needs attention: network congestion may happen if a single packet can generate millions of concurrent replies, all directed to the same endpoint. Adding a Reflected Test Packet Control TLV allows Session-Sender to limit the number of replies. It may do so by selecting Session-Reflectors, for example:

  • Randomly by specifying a Layer 2 Address Group Sub-TLV: for example, setting the EUI-48 Address Group Mask to 0xF and the EUI-48 Address Group to 0x1. As a result, only 1 out of 16 reflectors will reply;
  • Having a specific vendor NIC by specifying a Layer 2 Address Group Sub-TLV with the EUI-48 Address Group Mask set to 0xFFFFFF000000;
  • Belonging to specific IP networks, for example, a subnet dedicated to IPv6 over IPv4 encapsulation by specifying the appropriate Layer 3 Address Group Sub-TLV.

Multicast traffic is also intrinsically asymmetrical, and focus on the return path is usually limited. The Length of the Reflected Packet value can be used to ensure the reflected packet transports all the timestamps and requested information, crucial for the underlying measure, but is as short as possible so as not to flood the network with useless data.

[I-D.ietf-ippm-stamp-srpm] defines the Return Path TLV that, when used in the combination with the Return Address Sub-TLV, allows a Session-Sender to request the reflected packet be sent to a different address from the Session-Sender one. These STAMP extensions could be used in combination with the Reflected Packet Control TLV, defined in this document, to direct the reflected STAMP test packets to a collector of measurement data (according to the [RFC7594]) for further processong and network analytics. An example of the use case could be used in the multicast scenario when, for example, the Session-Sender is close to the actual multicast frames generator (for example, a camera transmitting live video) so that the test packets follow the same path as the video stream packets in one direction. The data center where the test data are analyzed could be far away, and it would be better to have reflected packets return there.

5. Security Considerations

Security considerations discussed in [RFC8762],[RFC8972], and [I-D.ietf-ippm-stamp-srpm] apply to this document. Furthermore, spoofed STAMP test packets with the Reflected Test Packet Control TLV can be exploited to conduct a Denial-of-Service attack. Hence, implementations MUST use an identity protection mechanism. For example, verify the information about the source of the STAMP packet against a pre-defined list of trusted nodes. Also, STAMP authentication mode [RFC8762] or HMAC TLV [RFC8972] could be used for a STAMP test session containing the Reflected Test Packet Control TLV.

Considering the potential number of reflected packets that can be generated by a single test packet sent to a Multicast address, when sending such messages a Session-Sender SHOULD sign packets using the HMAC TLV.

6. Acknowledgments

TBA

7. IANA Considerations

7.1. Reflected Test Packet Control TLV Type

The IANA is requested to assign a new value for the Reflected Test Packet Control TLV from the STAMP TLV Types sub-registry according to Table 1.

Table 1: New Reflected Test Packet Control Type TLV
Value Description Reference
 TBA1 Reflected Test Packet Control TLV This document

7.2. Reflected Test Packet Control TLV Type

The IANA is requested to assign a new value for the Reflected Test Packet Control TLV from the STAMP Sub-TLV Types sub-registry according to Table 2.

Table 2: STAMP sub-TLV Types for the Reflected Test Packet Control TLV
Value Description TLV Used Reference
 TBA2 Layer 2 Address Group Reflected Test Packet Control TLV This document
 TBA3 Layer 3 Address Group Reflected Test Packet Control TLV This document

8. References

8.1. Normative References

[I-D.ietf-ippm-stamp-srpm]
Gandhi, R., Filsfils, C., Chen, M., Janssens, B., and R. F. Foote, "Simple TWAMP (STAMP) Extensions for Segment Routing Networks", Work in Progress, Internet-Draft, draft-ietf-ippm-stamp-srpm-18, , <https://datatracker.ietf.org/doc/html/draft-ietf-ippm-stamp-srpm-18>.
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
[RFC7594]
Eardley, P., Morton, A., Bagnulo, M., Burbridge, T., Aitken, P., and A. Akhter, "A Framework for Large-Scale Measurement of Broadband Performance (LMAP)", RFC 7594, DOI 10.17487/RFC7594, , <https://www.rfc-editor.org/info/rfc7594>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/info/rfc8174>.
[RFC8762]
Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple Two-Way Active Measurement Protocol", RFC 8762, DOI 10.17487/RFC8762, , <https://www.rfc-editor.org/info/rfc8762>.
[RFC8972]
Mirsky, G., Min, X., Nydell, H., Foote, R., Masputra, A., and E. Ruffini, "Simple Two-Way Active Measurement Protocol Optional Extensions", RFC 8972, DOI 10.17487/RFC8972, , <https://www.rfc-editor.org/info/rfc8972>.

8.2. Informative References

[RFC7497]
Morton, A., "Rate Measurement Test Protocol Problem Statement and Requirements", RFC 7497, DOI 10.17487/RFC7497, , <https://www.rfc-editor.org/info/rfc7497>.

Authors' Addresses

Greg Mirsky
Ericsson
Ernesto Ruffini
OutSys
via Caracciolo, 65
20155 Milano
Italy
Henrik Nydell
Accedian Networks