Wireshark-dev: Re: [Wireshark-dev] ATM over Ethernet
From: Alex Bennée <kernel-hacker@xxxxxxxxxx>
Date: Wed, 7 Nov 2012 12:08:48 +0000
On 6 November 2012 18:24, Guy Harris <guy@xxxxxxxxxxxx> wrote:
> On Nov 6, 2012, at 9:47 AM, Alex Bennée <kernel-hacker@xxxxxxxxxx> wrote:
>
>> I guess the real question is do I add options to the ATM decoder to
>> select AAL based on VPI/VCI?
>
> That sounds like a good idea.

Hmm so it's a chicken and egg problem. The ATMoE dissector doesn't
know if a flow is a given VPI.VCI because it hands that off to the
dissector. However the ATM dissector is expecting the higher layer to
have set the pseudo_header->atm.aal for it. Other dissectors do
already do this although most of them seem to be peeking into the ATM
header themselves to do this.

It looks as though the correct way would be to refactor the ATM
dissector but that could get messy.

>
> (At some point we might want to generalize the current notion of "conversations" to abstract away its orientation towards address-and-port-number endpoints, so that address-and-port-number transport-layer conversations are just one subtype, have it subsume the notion of "circuits", and use them in a number of places, including ATM virtual circuits, and add support for dissectors adding arbitrary properties to conversations; that could be used to assign not only AAL types to ATM virtual circuits, but to assign higher-level encapsulation/protocol values, complete with a UI to let the user specify them.)
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-- 
Alex, homepage: http://www.bennee.com/~alex/
http://www.half-llama.co.uk