Internet DRAFT - draft-boucadair-opsawg-rfc7125-update

draft-boucadair-opsawg-rfc7125-update







Operations and Management Area                              M. Boucadair
Internet-Draft                                                    Orange
Updates: 7125 (if approved)                               5 January 2023
Intended status: Informational                                          
Expires: 9 July 2023


   An Update to the tcpControlBits IP Flow Information Export (IPFIX)
                          Information Element
                draft-boucadair-opsawg-rfc7125-update-02

Abstract

   RFC 7125 revised the tcpControlBits IP Flow Information Export
   (IPFIX) Information Element that was originally defined in RFC 5102
   to reflect changes to the TCP Flags header field since RFC 793.
   However, that update is still problematic for interoperability
   because some flag values were deprecated since then.

   This document updates RFC 7125 by removing stale information from the
   IPFIX registry and avoiding future conflicts with the authoritative
   TCP Header Flags registry.

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 9 July 2023.

Copyright Notice

   Copyright (c) 2023 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.



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   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 Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  An Update to tcpControlBits IP Flow Information Export (IPFIX)
           Information Element . . . . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   TCP defines a set of control bits (also known as "flags") for
   managing connections.  The "Transmission Control Protocol (TCP)
   Header Flags" registry was initially set by [RFC3168], but it was
   populated with only TCP control bits that were defined in [RFC3168].
   [RFC9293] fixed that by moving that registry to be listed as a
   subregistry under the "Transmission Control Protocol (TCP)
   Parameters" registry, adding bits that had previously been specified
   in [RFC0793], and removing the NS (Nonce Sum) bit as per [RFC8311].
   Also, [RFC9293] introduces "Bit Offset" to ease referencing each
   header flag's offset within the 16-bit aligned view of the TCP header
   (Section 3.1 of [RFC9293]).  [TCP-FLAGS] is thus settled as the
   authoritative reference for the assigned TCP control bits.

   [RFC7125] revised the tcpControlBits IP Flow Information Export
   (IPFIX) Information Element (IE) that was originally defined in
   [RFC5102] to reflect changes to the TCP Flags header field since
   [RFC0793].  However, that update is still problematic for
   interoperability because a value was deprecated since then (Section 7
   of [RFC8311]) and, therefore, [RFC7125] risks to deviate from the
   authoritative TCP registry [TCP-FLAGS].

   This document fixes that problem by removing stale information from
   the IPFIX registry and avoiding future conflicts with the
   authoritative TCP registry.





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   Also, because the setting of control bits may be misused in some
   flows (e.g., DDoS attacks), an exporter has to report all observed
   control bits even if no meaning is associated with a given TCP flag.
   This document uses a stronger requirement language compared to
   [RFC7125].  See Section 3 for more details.

2.  Terminology

   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 2 of [RFC7011].

3.  An Update to tcpControlBits IP Flow Information Export (IPFIX)
    Information Element

   This document updates Section 3 of [RFC7125] as follows:

   OLD:
      The values of each bit are shown below, per the definition of the
      bits in the TCP header [RFC0793][RFC3168] [RFC3540]:



























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             MSb                                                         LSb
        0   1   2   3   4   5   6   7   8   9  10  11  12  13  14  15
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
      |               |           | N | C | E | U | A | P | R | S | F |
      |     Zero      |   Future  | S | W | C | R | C | S | S | Y | I |
      | (Data Offset) |    Use    |   | R | E | G | K | H | T | N | N |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

      bit    flag
      value  name  description
      ------+-----+-------------------------------------
      0x8000       Zero (see tcpHeaderLength)
      0x4000       Zero (see tcpHeaderLength)
      0x2000       Zero (see tcpHeaderLength)
      0x1000       Zero (see tcpHeaderLength)
      0x0800       Future Use
      0x0400       Future Use
      0x0200       Future Use
      0x0100   NS  ECN Nonce Sum
      0x0080  CWR  Congestion Window Reduced
      0x0040  ECE  ECN Echo
      0x0020  URG  Urgent Pointer field significant
      0x0010  ACK  Acknowledgment field significant
      0x0008  PSH  Push Function
      0x0004  RST  Reset the connection
      0x0002  SYN  Synchronize sequence numbers
      0x0001  FIN  No more data from sender

      As the most significant 4 bits of octets 12 and 13 (counting from
      zero) of the TCP header [RFC0793] are used to encode the TCP data
      offset (header length), the corresponding bits in this Information
      Element MUST be exported as zero and MUST be ignored by the
      collector.  Use the tcpHeaderLength Information Element to encode
      this value.

      Each of the 3 bits (0x800, 0x400, and 0x200), which are reserved
      for future use in [RFC0793], SHOULD be exported as observed in the
      TCP headers of the packets of this Flow.

   NEW:
      As per [RFC9293], the assignment of the TCP control bits is
      managed by IANA from the "TCP Header Flags" registry [TCP-FLAGS].
      That registry is authoritative to retrieve the most recent TCP
      control bits.

      As the most significant 4 bits of octets 12 and 13 (counting from
      zero) of the TCP header [RFC9293] are used to encode the TCP data
      offset (header length), the corresponding bits in this Information



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      Element MUST be exported as zero and MUST be ignored by the
      collector.  Use the tcpHeaderLength Information Element to encode
      this value.

      All TCP control bits (including unassigned) MUST be exported as
      observed in the TCP headers of the packets of this Flow.

4.  IANA Considerations

   IANA is requested to update the "tcpControlBits" entry of the [IPFIX]
   as follows:

   *  Update the description of to reflect the change in Section 3.

   *  Add [TCP-FLAGS] to the Additional Information field.

   *  Add this document to the references


5.  Security Considerations

   This document does not add new security considerations to those
   already discussed in Section 5 of [RFC7125].

6.  Acknowledgements

   This document was triggered by a discussion in opswag with the
   authors of [I-D.ietf-opsawg-ipfix-srv6-srh].

7.  References

7.1.  Normative References

   [RFC2119]  Bradner, S. and RFC Publisher, "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>.

   [RFC7011]  Claise, B., Ed., Trammell, B., Ed., Aitken, P., and RFC
              Publisher, "Specification of the IP Flow Information
              Export (IPFIX) Protocol for the Exchange of Flow
              Information", STD 77, RFC 7011, DOI 10.17487/RFC7011,
              September 2013, <https://www.rfc-editor.org/info/rfc7011>.

   [RFC7125]  Trammell, B., Aitken, P., and RFC Publisher, "Revision of
              the tcpControlBits IP Flow Information Export (IPFIX)
              Information Element", RFC 7125, DOI 10.17487/RFC7125,
              February 2014, <https://www.rfc-editor.org/info/rfc7125>.



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   [RFC8174]  Leiba, B. and RFC Publisher, "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>.

   [RFC9293]  Eddy, W., Ed. and RFC Publisher, "Transmission Control
              Protocol (TCP)", STD 7, RFC 9293, DOI 10.17487/RFC9293,
              August 2022, <https://www.rfc-editor.org/info/rfc9293>.

   [TCP-FLAGS]
              IANA, "TCP Header Flags",
              <https://www.iana.org/assignments/tcp-parameters/tcp-
              parameters.xhtml#tcp-header-flags>.

7.2.  Informative References

   [I-D.ietf-opsawg-ipfix-srv6-srh]
              Graf, T., Claise, B., and P. Francois, "Export of Segment
              Routing over IPv6 Information in IP Flow Information
              Export (IPFIX)", Work in Progress, Internet-Draft, draft-
              ietf-opsawg-ipfix-srv6-srh-06, 5 January 2023,
              <https://datatracker.ietf.org/api/v1/doc/document/draft-
              ietf-opsawg-ipfix-srv6-srh/>.

   [IPFIX]    IANA, "IP Flow Information Export (IPFIX) Entities",
              <https://www.iana.org/assignments/ipfix/ipfix.xhtml>.

   [RFC0793]  Postel, J. and RFC Publisher, "Transmission Control
              Protocol", RFC 793, DOI 10.17487/RFC0793, September 1981,
              <https://www.rfc-editor.org/info/rfc793>.

   [RFC3168]  Ramakrishnan, K., Floyd, S., Black, D., and RFC Publisher,
              "The Addition of Explicit Congestion Notification (ECN) to
              IP", RFC 3168, DOI 10.17487/RFC3168, September 2001,
              <https://www.rfc-editor.org/info/rfc3168>.

   [RFC5102]  Quittek, J., Bryant, S., Claise, B., Aitken, P., Meyer,
              J., and RFC Publisher, "Information Model for IP Flow
              Information Export", RFC 5102, DOI 10.17487/RFC5102,
              January 2008, <https://www.rfc-editor.org/info/rfc5102>.

   [RFC8311]  Black, D. and RFC Publisher, "Relaxing Restrictions on
              Explicit Congestion Notification (ECN) Experimentation",
              RFC 8311, DOI 10.17487/RFC8311, January 2018,
              <https://www.rfc-editor.org/info/rfc8311>.

Author's Address




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   Mohamed Boucadair
   Orange
   35000 Rennes
   France
   Email: mohamed.boucadair@orange.com














































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