Re: Proposal for PSAMP-PROTO section 6.5.2.6

[Andrew Johnson <andrjohn@cisco.com>]

Hi all

There is a contradiction in the proposed text that I would like to
correct.

Andrew Johnson wrote:
[SNIP]
> 6.5.2.6 Hash-Based Filtering
[SNIP]
> For the bytes taken from the IP payload, IPSX has a fixed offset
> of 0 bytes and a fixed size of 8 bytes.  The number and offset of
> payload bytes in the BOB function MUST be configurable.  If any
> of the configured set of bytes from the IP payload are unavailable
> then 0 MUST be used, which may result in a different value than
> if the hash function is run on a subset of the input.

Here, for a hash function with a variable length input, it says that
you must pass in 0 for the missing bytes.  This disagrees with the
text below and I would like to simply remove the last sentence.


> The minimum configuration ranges MUST be as follows:
>  Number of bytes:  from 8 to 32
>  Offset:           from 0 to 64
>
> If the selected payload bytes are not available and the hash function
> can take a variable sized input then the hash function MUST be run
> with the information which is available and a shorter size.  Passing
> 0 as a substitute for missing payload bytes is only acceptable if
> the hash function takes a fixed size as is the case with IPSX.

The above text is quite clear, and contrary to the previous original
paragraph.


regards

Andrew

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