Wireshark-dev: Re: [Wireshark-dev] 3GPP RLC and MAC protocols support
From: "Martin Mathieson" <[email protected]>
Date: Tue, 8 Jan 2008 18:49:22 +0000

On Jan 8, 2008 6:05 PM, Neil Piercy <[email protected]> wrote:
I'm looking at the same issue for my company and came to similar conclusion. At present we've gone down the route of (c) for a quick try, but I think it will soon be coming unstuck - it certainly isn't general enough to feed back yet.  We haven't yet got any MAC/RLC dissection, but would be happy to work with somebody to do so - even if we only leave the glue to transports as proprietary for now.

If it were to be done, I'd like to use the approach as I took with FP, where a filled-in-struct is attached to each frame with the info the dissector needs to know.  As you say, this can be filled in from wherever it is available or can be guessed.

I'd be interested in discussing what these fields should be if you like..  The FP dissector has been very useful to me - I'm not convinced that MAC and RLC would be as useful to me (one reason is that we have separate primitives/frames for the messages exchanged between the layers, so its not obvious how I'd be able to associate the frames and show the whole stack, i.e.

in one Wireshark frame.  Ciphering is another complication.


BTW is anyone planning on hooking RRC NAS message IEs into gsm_a_dtap ? Since RRC is from the ASN.1, I've not tried it yet, but any pointers appreciated.

From: [email protected] [mailto:[email protected]] On Behalf Of Martin Mathieson
Sent: 08 January 2008 11:26

To: Developer support list for Wireshark
Subject: Re: [Wireshark-dev] 3GPP RLC and MAC protocols support

I don't know of anyone working on MAC or RLC dissectors.

FP is currently only available for Catapult DCT2000 and Tektronix K12 file formats, since those formats include the information needed to interpret the message payloads.  This amounts to using Wireshark as a different log viewer, rather than as a passive network analyser.

In order to decode the MAC and RLC layers, you'd need to either:
(a) use a file format that gives you this information directly (as above), OR
(b) infer the FP/MAC/RLC layer configuration/state using information gleaned from RRC configuration messages, OR MAYBE
(c) guess from the message size/timing/contents that common transport formats have been used, e.g. there are standard settings using with AMR co-ordinated channels? OR EVEN LESS LIKELY
(d) get all of this information from preference settings.  I think this is probably a non-starter since so much of the information is per-channel or even per-frame.

I'd love to see someone do this, but know that it isn't trivial - my company (Catapult) built such an analyser (using (b) - before I joined).

I could have extended the approach of (a) for the DCT2000 format, i.e. dissect our own proprietary primitive headers then use this and other information in the file format to hand off to pure MAC or RLC dissectors (that would use attached information, as the FP dissector does), but this would still just be using Wireshark as a different log viewer, I don't know of any other file formats that would then be able to take advantage of these dissectors in the same way (possibly K12 again...).  I believe the headers for MAC and RLC are quite short, and that it would take more effort to dissect the proprietary headers than it would for the actual protocol headers.


On Jan 8, 2008 10:41 AM, Anders Broman <[email protected]> wrote:
An RRC dissector (packet-rrc.c) exists but only partly used. Some time
ago some one
asked about MAC and probably did something with it but nothing was
commited back to WS.
These are somewhere in the middle of the tread

-----Original Message-----
From: [email protected]
[mailto:[email protected] ] On Behalf Of
[email protected]
Sent: den 8 januari 2008 15:35
To: Developer support list for Wireshark
Subject: [Wireshark-dev] 3GPP RLC and MAC protocols support


Is anybody working on dissectors for 3GPP-UMTS- RLC and MAC protocols ?
Or are these dissectors already available somewhere ?

Thanks & Regards,

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