Cell Relay Archive

[albert.e.manfredi@boeing.com]

In article <70iun6$kc0@plains.NoDak.edu>,
  tinguely@plains.NoDak.edu (Mark Tinguely) wrote:
> In article <8690ibj855.fsf@ironbridgenetworks.com>,
> James Carlson  <carlson@ironbridgenetworks.com> wrote:
>
> >If you need or want either separate user authentication, IP address
> >assignment, or protocol use negotiation, then PPP provides that on an
> >ATM VC with very little overhead.
>
> good explaination.
>
> one place that PPP over ATM is being used is in the DSL world. The telephone
> network is becoming an ATM cloud, so a DSL connection looks something like:
>
> 				 voice				 voice
> 				   v				   ^
> 	ISP1  <-- ATM cloud --> telephone CO <-- DSL and voice --> home
> *Cable TV     <-||						   v
> *digital voice<--|						  data
>
> * with today's "last mile" data rates these are 'pipe dreams'.
> it appears now vendors are using a router on the home side to provide
> traditional LAN (IP, IPX, etc) protocols, but there is nothing stopping
> native ATM services to be offered.
>
> I am not sure if the QOS/bandwidth features, the telco's increasing
> use of ATM, or just wishful thinking is the driving force behind using
> ATM in these DSL products.

What seems to be missing here is that DSL was designed for ISDN over voice
grade cable, right? But now we're talking about ADSL, and in the future VDSL,
so the two 64 Kb/s + 16 Kb/s ISDN channels are not all we'll get. With ADSL,
you have a downstream capability of 6+ Mb/s, so what will you do with it?

If you use ATM to manage that bandwidth, you would then potentially be going
to your ISP over an ATM VC, no? If you do that, you would use PPP over that
ATM VC.

Your other option is to use ADSL for (a) the one 64 Kb/s voice channel, and
(b) the wide data channel, use IP only on that wide data channel, _and_
constrain yourself to using the telephone company CO as your ISP. I don't
know that you can do anything more with ADSL than that, unless you layer
something like ATM over it.

Whether ADSL is just a pipe dream is up to the RBOCs, I suspect, but if it
does become real, then if I were they, I would probably want to offer more
than just an IP data line over that bandwidth.

Bert
manfredi@arl.bna.boeing.com

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