Revision of the tcpControlBits IPFIX Information Element
draft-trammell-ipfix-tcpcontrolbits-revision-04

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IPFIX Working Group                                          B. Trammell
Internet-Draft                                                ETH Zurich
Intended status: Informational                                 P. Aitken
Expires: April 10, 2014                               Cisco Systems, Inc
                                                        October 07, 2013

        Revision of the tcpControlBits IPFIX Information Element
          draft-trammell-ipfix-tcpcontrolbits-revision-04.txt

Abstract

   This document revises the tcpControlBits IPFIX Information Element as
   originally defined in [RFC5102] to reflect changes to the TCP Flags
   header field since [RFC0793].

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
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   This Internet-Draft will expire on April 10, 2014.

Copyright Notice

   Copyright (c) 2013 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
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Internet-Draft            IPFIX tcpControlBits              October 2013

1.  Introduction

   Octets 12 and 13 of the TCP header encode the data offset (header
   length) in four bits, as well as 12 bits of flags.  The least
   significant 6 bits of these were defined in [RFC0793] as URG, ACK,
   PSH, RST, SYN, and FIN for TCP control.  Subsequently, [RFC3168]
   defined the CWR and ECE flags for Explicit Congestion Notification
   (ECN) negotiation and signaling; [RFC3540] additionally defined the
   NS flag for the ECN Nonce Sum.

   As defined in the IANA IPFIX Information Element Registry
   [IANA-IPFIX], taken from [RFC5102], the tcpControlBits Information
   Element for IPFIX [RFC7011] only covers the original six bits from
   [RFC0793].  To allow IPFIX to be used to measure the use of ECN, and
   to bring the IPFIX Information Element definition in line with the
   current definition of the TCP Flags header field, it is necessary to
   revise this definition.

   The revised definition of the Information Element in Section 2 was
   developed and approved through the IE-DOCTORS process [RFC7013] in
   August 2013.  Section 5.1 of [RFC7013] states "This process should
   not in any way be construed as allowing the IE-DOCTORS to overrule
   IETF consensus.  Specifically, Information Elements in the IANA IE
   registry which were added with IETF consensus require IETF consensus
   for revision or deprecation".  Since the tcpControlBits Information
   Element was defined in [RFC5102], an IETF Proposed Standard, any
   revision of this Information Element definition requires IETF
   Consensus.  The publication of this document fulfills that
   requirement.

   The following section defines the revised tcpControlBits Information
   Element as in Section 9.1 of [RFC7013].

2.  The tcpControlBits Information Element

   ElementId:   6
   Data Type:   unsigned16
   Data Type Semantics:   flags
   Description:   TCP control bits observed for the packets of this
      Flow.  This information is encoded as a bit field; for each TCP
      control bit, there is a bit in this set.  The bit is set to 1 if
      any observed packet of this Flow has the corresponding TCP control
      bit set to 1.  The bit is cleared to 0 otherwise.

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

Trammell & Aitken        Expires April 10, 2014                 [Page 2]
Internet-Draft            IPFIX tcpControlBits              October 2013

    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 |