Ethereal-users: Re: [Ethereal-users] Broadband Modems

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From: Guy Harris <guy@xxxxxxxxxx>
Date: Fri, 17 Aug 2001 20:43:36 -0700 (PDT)
> An issue which is cropping up & will do more in the future
> is the need to analyse the encapsulated packet stream
> between a broadband modem (in our case Alcatel ADSL)
> & the client's router to determine causes of problems
> 
> Can anyone advise re ethereal capability in this area or point
> me to any resources on the subject. Could not see any mention of
> this in the documentation online

What sort of Alcatel ADSL modem?

What sort of encapsulated packet stream?  And in what is encapsulated? 
Is this an Ethernet or an ATM-25 interface?

Alcatel home modems, when using the Ethernet interface, just send
un-encapsulated Ethernet packets, so presumably that's not what you're
referring to (especially given that you said "client's router", as that
sounds more like a business DSL system).

If it's Ethernet, then Ethereal does support PPPoE, if that's what's
being used.

If it's ATM-25, then

	1) whether you can snoop traffic on your ATM-25 interface
	   depends on whether the raw packet capture mechanism on the
	   machine with the ATM-25 interface allows it, and whether
	   libpcap supports that;

	2) Ethereal can handle "raw ATM" (as in "frames are, for
	   example, AAL5 PDUs), although we'd need to add a new DLT_
	   type to libpcap for "raw ATM".  There's no PPPoA support,
	   however.