One document matched: draft-trammell-ipfix-tcpcontrolbits-revision-00.xml
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<!DOCTYPE rfc SYSTEM "rfc2629.dtd">
<rfc ipr="trust200902" category="info" docName="draft-trammell-ipfix-tcpcontrolbits-revision-00.txt">
<?rfc compact="yes"?>
<?rfc subcompact="yes"?>
<?rfc toc="no"?>
<?rfc symrefs="yes"?>
<front>
<title abbrev="IPFIX tcpControlBits">
Revision of the tcpControlBits IPFIX Information Element
</title>
<author initials="B." surname="Trammell" fullname="Brian Trammell">
<organization abbrev="ETH Zurich">
Swiss Federal Institute of Technology Zurich
</organization>
<address>
<postal>
<street>Gloriastrasse 35</street>
<city>8092 Zurich</city>
<country>Switzerland</country>
</postal>
<phone>+41 44 632 70 13</phone>
<email>trammell@tik.ee.ethz.ch</email>
</address>
</author>
<author initials="P." surname="Aitken" fullname="Paul Aitken">
<organization abbrev="Cisco Systems, Inc">
Cisco Systems, Inc.
</organization>
<address>
<postal>
<street>96 Commercial Quay</street>
<city>Commercial Street, Edinburgh EH6 6LX</city>
<country>United Kingdom</country>
</postal>
<phone>+44 131 561 3616</phone>
<email>paitken@cisco.com</email>
</address>
</author>
<date year="2013" month="September" day="6"/>
<area>Operations</area>
<workgroup>IPFIX Working Group</workgroup>
<abstract>
<t>This document revises the tcpControlBits IPFIX Information Element defined in <xref target="RFC5102"/> to reflect changes to the TCP Flags header field since <xref target="RFC0793"/>.</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>The first 16 bits of the TCP header contain four bits of encoded header
length as well as 12 bits of flags. The least significant 6 bits of these
were defined in <xref target="RFC0793"/> as URG, ACK, PSH, RST, SYN, and
FIN for TCP control. Subsequently, <xref target="RFC3168"/> defined the CWR
and ECE flags for Explicit Congestion Notification (ECN) negotiation and
signaling; <xref target="RFC3540"/> additionally defined the NS flag for
the ECN Nonce Sum.</t>
<t>As defined in <xref target="IANA-IPFIX">the IANA IPFIX Information
Element Registry</xref>, taken from <xref target="RFC5102"/>, the
tcpControlBits Information Element for <xref
target="I-D.ietf-ipfix-protocol-rfc5101bis">IPFIX</xref> only covers the
original six bits from <xref target="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.</t>
<t>The revised definition of the Information Element in <xref
target="sec-ie"/> was developed and approved through the IE-DOCTORS process
<xref target="I-D.ietf-ipfix-ie-doctors"/> in August 2013. Section 5.1 of
<xref target="I-D.ietf-ipfix-ie-doctors"/> 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
<xref target="RFC5102"/>, an IETF Proposed Standard, any revision of this
Information Element definition requires IETF Consensus. The publication of
this document fulfills that requirement.</t>
<t>The following section defines the revised tcpControlBits Information
Element as in Section 9.1 of <xref target="I-D.ietf-ipfix-ie-doctors"/>.</t>
</section>
<section title="The tcpControlBits Information Element" anchor="sec-ie">
<t><list style="hanging">
<t hangText="ElementId: ">6</t>
<t hangText="Data Type: ">unsigned16</t>
<t hangText="Data Type Semantics: ">flags</t>
<t hangText="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.<vspace/><vspace/>
The values of each bit are as follows, following the current
definition of the bits in the TCP header:</t>
</list></t>
<figure><artwork>
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 |
| Header Length | Reserved | S | W | C | R | C | S | S | Y | I |
| | | | 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
</artwork></figure>
<t><list style="hanging">
<t>As the most significant four bits of this header are used to encode
the TCP header length, they must be exported as zero and must be ignored
by the collector.<vspace/><vspace/>
The three future use bits (0x800, 0x400, and 0x200) should be exported
as one if those bits are observed in the TCP headers of the packets of
this Flow, as they may be subsequent to a future update of <xref
target="RFC0793"/>.<vspace/><vspace/>
If exported as a single octet with reduced length encoding, this
Information Element covers the low-order octet of this field (i.e, bits
0x80 to 0x01), omitting the ECN Nonce Sum and the three reserved bits. A
collector receiving this Information Element with reduced length encoding
must not assume anything about the content of these four
bits.<vspace/><vspace/>
Note that previous revisions of this Information Element's definition
specified that the CWR and ECE bits must be exported as zero, even if
observed. Collectors should therefore not assume that a value of zerp for
these bits in this Information Element indicates the bits were never set
in the observed traffic, especially if these bits are zero in every Flow
Record sent by a given exporter.</t>
<t hangText="References: "><xref target="RFC0793"/><xref target="RFC3168"/><xref target="RFC3540"/></t>
<t hangText="Revision:">1</t>
</list></t>
</section>
<section title="IANA Considerations">
<t>IANA will update the definition of the tcpControlBits Information Element in the <xref target="IANA-IPFIX">the IANA IPFIX Information Element Registry</xref> to reflect the changes in <xref target="sec-ie"/> above.</t>
</section>
<section title="Security and Privacy Considerations">
<t>This document has no security or privacy considerations; the security considerations for <xref target="I-D.ietf-ipfix-protocol-rfc5101bis">IPFIX</xref> apply.</t>
</section>
<section title="Acknowledgments">
<t>Thanks to Andrew Feren for comments on the revised definition. This work
is partially supported by the European Commission under grant agreement
FP7-ICT-318627 mPlane; this does not imply endorsement by the
Commission.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.I-D.ietf-ipfix-protocol-rfc5101bis" ?>
<?rfc include="reference.I-D.ietf-ipfix-ie-doctors" ?>
<?rfc include="reference.RFC.0793" ?>
<?rfc include="reference.RFC.3168" ?>
<?rfc include="reference.RFC.3540" ?>
</references>
<references title="Informative References">
<?rfc include="reference.RFC.5102" ?>
<reference anchor='IANA-IPFIX'>
<front>
<title>IP Flow Information Export Information Elements (http://www.iana.org/assignments/ipfix)</title>
<author surname="Internet Assigned Numbers Authority"/>
<date/>
</front>
</reference>
</references>
</back>
</rfc>| PAFTECH AB 2003-2026 | 2026-04-24 05:41:28 |