Re: Link layer headers in reports?

[Peram Marimuthu <peram@cisco.com>]

Andy Bierman wrote:

> At 08:50 AM 11/26/2002 -0500, albert@research.att.com wrote:
> >Hi Peram,
> >
> >It is important to somehow get link layer header information.  Is your

How is link layer header used?

>
> >suggestion that this information be exported, but without any extraction
> >and formating?
>
> I think he is asking for the opposite -- for the sample source to
> strip off all headers before L3.  This would make it easier for
> the collector to decode the sample slice.  Another option is
> to include the byte offset into the captured packet slice of
> the L3 header.

Stripping of all headers before L3 will make it easy for collector.
Including L2 will mean that collector will have to understand all types
of L2, and the exporter needs to tell the collector about the type
of interface (POS/Ethernet etc) when it sends packet samples.


>
>
> I want to make sure that we don't define so much 'baseline'
> functionality that PSAMP will be too hard to implement in HW.
> A minimal implementation will select packets without examining
> them (e.g., 1 in N) and will only be capable of exporting the
> first N bytes of these samples.

I agree. Perhaps we can make stripping optional for those who want
to save on export b/w and who dont care about link layer headers.

Peram

>
>
> Additional functionality, above this baseline, should not be
> mandatory.  The market will decide what features are important.
>
> >-- Albert
>
> Andy
>
> >> Section 5 of the framework document says, "Information
> >> eligible for inclusion in packet reports includes (i)
> >>    the packet content itself (including encapsulating headers); "
> >>
> >> Is there a need to include link layer headers in this export?
> >> Drawback of this will be that the collector will have to know
> >> which type of interface originated this report and understand
> >> every possible link layer (PPP/HDLC/Ethernet/FR etc) before
> >> the data can be interpreted.
> >>
> >> An alternate approach would be to identify the network layer
> >> and provide raw ipv4/ipv6/mpls packet.
> >>
> >> Peram
> >>
> >>
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> >>
> >
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