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List:       nanog
Subject:    Re: Topological significance of transport technologies [Was: Re:
From:       Robert Bowman <rob () elite ! exodus ! net>
Date:       1997-07-02 0:34:26
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Agreed..  the distinction between the two layers is becoming somewhat
more and more vague by the day, especially with companies like Ipsilon
and with Cisco's integration of eclipse switching and/or the RSM into
the Catalyst..  how the two layers interact is really the only
importance to the IP packet.

rob
> 
> At 05:00 PM 07/01/97 -0700, Robert Bowman wrote:
> 
> >layer 2 vs. layer 3
> >
> >tis like comparing a motorcyle to an automobile--both get you places
> >but in fairly different ways
> >
> 
> I shouldn't be contributing to this thread, but what the hell.
> 
> Its not really Layer 2 vs. Layer 3, its how to integrate the
> two layers and make it work. Mike O'Dell is fond of saying,
> "Pure Layer 3 routed networks are dead," and I can understand
> his point, although I don't necessarily agree with it. I do
> understand, and I think its important for everyone else
> to understand the point here.
> 
> Yes, they both get you there, but the pertinent summary to be
> drawn from this comparison is that 'you' are the IP packet,
> and you really don't care what the mode of transport is (e.g.
> frame-relay, leased point-to-point lines, ATM). Each provide
> a pipe. Some have more intrinsic flexibility than others (e.g.
> virtual circuits) and therefore represent a significant reason
> to employ a specific technology over another, given pricing, and
> geographic availability.
> 
> Again, IP packets don't really care if it's a motorcycle, an
> airplane, or an automobile (unless its a Harley :-).
> 
> It should also be noted that some technologies, such as
> frame-relay are used only in *topologically significant*
> places, ie. customer aggregation, for precisely these
> reasons. In some networks, frame-relay is used for
> customer aggregation, fast-ethernet is used in the PoP,
> and ATM is used in the wide-area (just an example).
> 
> - paul
> 

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