Wireshark · Wireshark-users: Re: [Wireshark-users] capture Q931 protocol

[Guy Harris <guy@xxxxxxxxxxxx>]

On Jan 19, 2009, at 3:30 AM, Gopalakrishnan A.N wrote:

>    thanks for the reply, the sample data captured is attached with  
> this mail. Its they call as G711 data.

G.711 is an audio coding standard, so if it's G.711 data, there's no Q. 
931 - Q.931 is used for signaling on ISDN (and other forms of digital  
telephony), and G.711 is used for audio on various forms of digital  
telephony (as well as in, for example, .au files).

So is it Q.931 (containing signaling to set up the call) or is it G. 
711 (for the audio of the call)?  The text file seems to show the data  
as being divided into variable-length packets, which sounds more like  
Q.931 (possibly atop LAPD) rather than G.711 (which doesn't have any  
notion of packet boundaries).  However, the packet data doesn't look  
too much like Q.931, whether atop LAPD or not.