Re: [Ethereal-dev] New dissector gprs-llc ,patch packet-bssgp.c

[<jkor@xxxxxxxx>]

By my understanding there are differences. The structure of frame is similar: address field, control field , data , FCS. The control field for instance in 802.2LLC,HDLC .. is 1 or 2 bytes, but in GPRS LLC it is variable length max 36 bytes long. 
   There are three types of frames in both protocols. The type of frame is determined with least significant two bits of control byte in HDLC, but with two most significant bits of control byte in LLC GPRS. The P/F bit is used only in U frames. The FCS is 3 bytes long. ...

                       Josef



----- Původní zpráva -----
Odesílatel: Guy Harris <gharris@xxxxxxxxx>
Datum: Středa, 7.dubna 2004 - 8:37 dop.
Předmět: Re: [Ethereal-dev] New dissector gprs-llc ,patch packet-bssgp.c

> On Tue, Apr 06, 2004 at 12:10:28PM +0200, jkor@xxxxxxxx wrote:
> > I am sending dissector for next layer(LLC) of GPRS Gb line stack
> 
> Is this an HDLC-style protocol, with a control field like 802.2 LLC,
> LAPB, LAPD, etc.?
> 
> If so, you might want to use the routines in "xdlc.c" to dissect the
> control field.
> 
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