Subject: [IPFIX] [Fwd: [Technical Errata Reported] RFC3954 (2096)]

From: Paul Aitken <[email-masked]>
Date: Thu, 25 Mar 2010 18:45:18 +0000

FYI, I've opened a new errata on RFC 3954:

The following errata report has been submitted for RFC3954,
"Cisco Systems NetFlow Services Export Version 9".

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You may review the report below and at:
http://www.rfc-editor.org/errata_search.php?rfc=3954&eid=2096

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Type: Technical
Reported by: Paul Aitken <[email-masked]>

Section: 5.3 and 6.2.

Original Text
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    Padding

          The Exporter SHOULD insert some padding bytes so that the
          subsequent FlowSet starts at a 4-byte aligned boundary.  It is
          important to note that the Length field includes the padding
          bytes.  Padding SHOULD be using zeros.

Corrected Text
--------------
    Padding

          The Exporter SHOULD insert some padding bytes so that the
          subsequent FlowSet starts at a 4-byte aligned boundary.  It is
          important to note that the Length field includes the padding
          bytes.  The padding length MUST be shorter than any allowable
          record in the Set.  Padding SHOULD be using zeros.

Notes
-----
Addition of "The padding length MUST be shorter than any allowable
record in the Set."

With small field sizes, such that the record size <= 3, it's not
possible to distinguish padding from further data records (s 5.3) or
options data records (s 6.2).

eg, with a record length of 3, three records will consume 9 octets.
Three octets of padding will be added to this, giving a total length of
12 octets. The 12 octets now look like *four* records. In this case,
padding is NOT appropriate.

NB1 the same paragraph in section 6.1 is NOT affected, because the fixed
size of the other fields dictates that the only possibility is padding
of 2 octets.

NB2 this situation is anticipated in IPFIX (RFC 5101), from which the
additional text is taken.

Instructions:
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This errata is currently posted as "Reported". If necessary, please
use "Reply All" to discuss whether it should be verified or
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Editorial Board)
can log in to change the status and edit the report, if necessary.

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RFC3954 (draft-claise-netflow-9-08)
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Title               : Cisco Systems NetFlow Services Export Version 9
Publication Date    : October 2004
Author(s)           : B. Claise, Ed.
Category            : INFORMATIONAL
Source              : INDEPENDENT
Area                : N/A
Stream              : INDEPENDENT
Verifying Party     : ISE & Editorial Board

-- 
Paul Aitken
Cisco Systems Ltd, Edinburgh, Scotland.
http://www.cisco.com/web/about/doing_business/legal/cri/index.html