Wireshark · Ethereal-dev: Re: [Ethereal-dev] PPP dissector bug

[Irfan Khan <ikhan@xxxxxxxxxxxx>]

Yup, these are framing bytes.  I thought it better to put the check for 
any unexpected 0x7e s in packet-ppp to make it more bug-proof :)

Guy Harris wrote:

> On Mon, Mar 10, 2003 at 07:38:08PM -0700, Irfan Khan wrote:
>  
>
> > I was looking at a log, using ethereal, where the packets were PPP over 
> > L2TP.  The L2TP dissector was calling the PPP HDLC handler correctly 
> > however the PPP dissector was unable to make make sense of the packets 
> > because they had a 0x7e in the beginning.
> >    
>
> What are the 0x7e's?  They're presumably not framing bytes, as RFC 2661
> says:
>
> 	5.3 Forwarding PPP Frames
>
> 	   Once tunnel establishment is complete, PPP frames from the remote
> 	   system are received at the LAC, stripped of CRC, link framing, and
> 	   transparency bytes, encapsulated in L2TP, and forwarded over the
> 	   appropriate tunnel. The LNS receives the L2TP packet, and processes
> 	   the encapsulated PPP frame as if it were received on a local PPP
> 	   interface.
>