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RFC 5101, "Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of IP Traffic Flow Information", January 2008

Note: This RFC has been obsoleted by RFC 7011

Source of RFC: ipfix (ops)

Errata ID: 2791
Status: Verified
Type: Technical

Reported By: Adrian Farrel
Date Reported: 2011-04-28
Verifier Name: Dan Romascanu
Date Verified: 2011-08-02

Section 7 says:

   If the length of the Information Element is greater than or equal to
   255 octets, the length is encoded into 3 octets before the
   Information Element.  The first octet is 255, and the length is
   carried in the second and third octets, as shown in Figure S.

It should say:

   The length may also be encoded into 3 octets before the Information
   element allowing the length of the Information Element to be
   greater than or equal to 255 octets. In this case, first octet of
   the Lenght field MUST be 255, and the length is carried in the 
   second and third octets, as shown in Figure S.

Notes:

The original text is ambiguous as to whether it is possible to carry a length of less than 255 encoded in a 3 octet Length field. The quoted text seems to say it is not allowed, but Figure S says that the 2nd and 3rd octets may be set to "Length (0 to 65535)".

Since there is absolutely no harm (except a little inefficiency) in using a 3 octet Length field to encode a small length, the document should be clarified to remove the ambiguity.

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