Internet-Draft IPFIX IE for UDP Options January 2023
Boucadair & Reddy.K Expires 27 July 2023 [Page]
Intended Status:
Standards Track
M. Boucadair
T. Reddy.K

Export of UDP Options Information in IP Flow Information Export (IPFIX)


This document specifies new IP Flow Information Export (IPFIX) Information Elements for UDP options.

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This Internet-Draft will expire on 27 July 2023.

Table of Contents

1. Introduction

IP Flow Information Export (IPFIX) [RFC7011] is a protocol that is widely deployed in operators networks for traffic management purposes. The protocol specifies the encoding of a set of basic data types and how the various Information Elements (IEs) are transmitted. In order to support the export of new flow-related measurement data, new IEs can be defined and registered in a dedicated IANA registry [IANA-IPFIX] for interoperability.

This document specifies new IPFIX Information Elements for UDP options (Section 5). A brief overview of UDP option is provided in Section 3.

2. Conventions and Definitions

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.

This document uses the terms defined in Section 3 of [I-D.ietf-tsvwg-udp-options] and [RFC7011].

3. UDP Options at a Glance

UDP [RFC0768] does not support an extension mechanism similar to the options supported by other transport protocols, such as TCP [RFC9293], SCTP [RFC9260], or DCCP [RFC4340]. Such a mechanism can be useful for various applications, e.g., discover a path MTU or share timestamps. To fill that void, [I-D.ietf-tsvwg-udp-options] extends UDP with a mechanism to insert extensions in datagrams. To do so, and unlike the conventional approach that relies upon transport headers, [I-D.ietf-tsvwg-udp-options] uses trailers. Concretely, UDP options are placed in the surplus area (that is, the area of an IP payload that follows a UDP packet). See Figure 1. An example of the use of UDP options is described in [I-D.ietf-tsvwg-udp-options-dplpmtud].

                       IP transport payload
| IP Hdr | UDP Hdr |     UDP user data    |   surplus area   |
                     UDP Length
Figure 1: Surplus Area

Section 5.1 introduces a new IE to export the observed UDP options.

Options indicated by Kind values in the range 0-191 are called SAFE options because they do not alter the UDP data payload. Such options can be silently ignored by receivers without affecting the meaning of the UDP user data (Section 9 of [I-D.ietf-tsvwg-udp-options]).

Options indicated by Kind values in the range 192-255 are called UNSAFE options. Such options are not safe to ignore (Section 10 of [I-D.ietf-tsvwg-udp-options]).

[I-D.ietf-tsvwg-udp-options] reserves two options for experiements: the Experimental option (EXP, Kind=127) for SAFE options and the UNSAFE Experimental option (UEXP, Kind=254). For both options, Experimental ID (ExIDs) are used to differentiate concurrent use of these options. Known ExIDs are expected to be registered within IANA. Section 5.2 specifies a new IPFIX to export observed ExIDs in the EXP options. Also, Section 5.3 specifies a new IPFIX to export observed ExIDs in the UEXP options. Only 16-bits ExIDs are supported.

This document does not intend to elaborate operational guidance/implications of UDP options. The document focuses exclusively on exporting observed UDP options in datagrams. The motivation for exporting such data is similar to the one for exporting TCP options (tcpOptions IE) or IPv6 Extension Headers (ipv6ExtensionHeaders).

4. Security Considerations

This document does not introduce new security considerations other than those already discussed in [RFC7012].

5. IANA Considerations

This document requests IANA to add the following new IEs to the IANA registry entitled "IP Flow Information Export (IPFIX) Entities" [IANA-IPFIX].

5.1. udpOptions

  • Name: udpOptions
  • ElementID: TBD1
  • Description: Observed UDP options of a Flow. The information is encoded in a set of bit fields. Multiple instances of the udpOptions IE are included to cover the 0-255 range (Figure 2); each 64 values are mapped to an IE with th order preserved. Options are mapped to bits according to their option numbers. Option number X is mapped to bit X[64] of the IE instance determined by the order "[1+X/64]". A bit is set to 1 (or 0) if the corresponding UDP option is observed (or not). For example, (1) if only option kinds =<63 are observed, then only one udpOptions IE instance is included, (2) if only option kinds =<127 are observed, then two udpOptions IEs instances are included, (3) if some option kinds =<63 while others are >=192 are observed, then four udpOptions IE instances are included with the second and third IE instances are set to 0, etc.
  • Abstract Data Type: unsigned64
  • Data Type Semantics: flags
  • Additional Information: [I-D.ietf-tsvwg-udp-options]. See the assignments in the "xxxx" IANA registry at URL_IANA_UDP_OPTIONS.
  • Reference: [This-Document]
    0-63      64-127    128-191    192-255
    Range      Range     Range       Range
Figure 2: Mapping of the UDP Options to the udpOptions IEs

5.2. udpExID

  • Name: udpExID
  • ElementID: TBD2
  • Description: Observed Expermients ID (ExIDs) in the Experimental option (EXP, Kind=127). The information is encoded in a set of 16-bit fields. Each 16-bit field carries the observed ExID in an EXP option.
  • Abstract Data Type: octetArray
  • Data Type Semantics: identifier
  • Additional Information: [I-D.ietf-tsvwg-udp-options]. See the assignments in the "xxxx" IANA registry at URL_IANA_UDP_ExIDs.
  • Reference: [This-Document]

5.3. udpUnsafeExID

  • Name: udpUnsafeExID
  • ElementID: TBD3
  • Description: Observed Expermients ID (ExIDs) in the UNSAFE Experimental option (UEXP, Kind=254). The information is encoded in a set of 16-bit fields. Each 16-bit field carries the observed ExID in an UEXP option.
  • Abstract Data Type: octetArray
  • Data Type Semantics: identifier
  • Additional Information: [I-D.ietf-tsvwg-udp-options]. See the assignments in the "xxxx" IANA registry at URL_IANA_UDP_ExIDs.
  • Reference: [This-Document]

6. References

6.1. Normative References

Touch, J. D., "Transport Options for UDP", Work in Progress, Internet-Draft, draft-ietf-tsvwg-udp-options-19, , <>.
Postel, J., "User Datagram Protocol", STD 6, RFC 768, DOI 10.17487/RFC0768, , <>.
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <>.
Claise, B., Ed., Trammell, B., Ed., and P. Aitken, "Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of Flow Information", STD 77, RFC 7011, DOI 10.17487/RFC7011, , <>.
Claise, B., Ed. and B. Trammell, Ed., "Information Model for IP Flow Information Export (IPFIX)", RFC 7012, DOI 10.17487/RFC7012, , <>.
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <>.

6.2. Informative References

Fairhurst, G. and T. Jones, "Datagram PLPMTUD for UDP Options", Work in Progress, Internet-Draft, draft-ietf-tsvwg-udp-options-dplpmtud-04, , <>.
"IP Flow Information Export (IPFIX) Entities", n.d., <>.
Kohler, E., Handley, M., and S. Floyd, "Datagram Congestion Control Protocol (DCCP)", RFC 4340, DOI 10.17487/RFC4340, , <>.
Stewart, R., Tüxen, M., and K. Nielsen, "Stream Control Transmission Protocol", RFC 9260, DOI 10.17487/RFC9260, , <>.
Eddy, W., Ed., "Transmission Control Protocol (TCP)", STD 7, RFC 9293, DOI 10.17487/RFC9293, , <>.


TODO acknowledge.

Authors' Addresses

Mohamed Boucadair
35000 Rennes
Tirumaleswar Reddy.K