Re: PSAMP: ipHeaderPacketSection and mplsLabelStackSection

[Falko Dressler <dressler@informatik.uni-erlangen.de>]

Paul,

this is indeed a difficult issue. At the first look, I was about saying
"yes, 1b) is the best solution because it provides the highest
flexibility". Nevertheless, I fear that many applications will derrive
that allow to monitor packet payload but do not offer to analyze the
packet header, i.e. such monitors are just "remote-pcap-devices". This
is quite fine but makes most of PSAMP functionality (IEs) unnecessary.

1a) is maybe too hard and 2) says "nothing"

so may final answer is either 2) or we need to elaborate a 1c)

Cheers,
Falko

Paul Aitken wrote:
> Dear psampers,
> 
> We have a new open issue in PSAMP-INFO:
> 
>   Should the ipHeaderPacketSection and mplsLabelStackSection also
>   report payload contents if the specified section length is longer
>   than the IP header or stack size, respectively?
> 
> 
> ipHeaderPacketSection is currently defined as:
> 
>       This information element carries a series of octets from the start
>       of the IP header of a sampled packet.
> 
> 
> mplsLabelStackSection is currently defined as:
> 
>       This information element carries the first n octets from the MPLS
>       label stack of a sampled packet.
> 
> 
> Potential resolutions include:
> 
> (1) We define the behaviour when the requested ipHeaderPacketSection
> or mplsLabelStackSectionsection size is larger than the actual amount of
> IP header / label stack data available.
> 
>   (1a) We define that only IP header / label stack octets are included.
> 
>   (1b) We define that the section contains a series of octets starting
>        from the beginning of the IP header / label stack and continuing
>        through the payload up to the limit of the available data.
> 
> (2) We say nothing, and leave it as implimentation defined behaviour.
> 
> 
> I believe that allowing these sections to continue into the payload per
> (1b) is potentially the most useful solution.
> 
> It saves configuring the capture of seperate header and payload elements
> where capture of the header and first few octets of the payload are
> desired for packet identification and analysis.
> 

-- 
Dr.-Ing. Falko Dressler
Computer Networks and Communication Systems
University of Erlangen-Nuremberg, Germany
Phone: +49 9131 85-27914 / Fax: +49 9131 85-27409
EMail: dressler@informatik.uni-erlangen.de / fd@acm.org
WWW: http://www7.informatik.uni-erlangen.de/~dressler/

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