Cell Relay Archive

[albert.e.manfredi@boeing.com]

In article <3607ec4b.14891717@cti-fw1.critical.com>,
  stu@critical.com (Stu  Card) wrote:
> After slogging through material on CLIP, MARS, LANE, NHRP, MPOA, RSVP,
> etc., I still have the question with which I started:
>
> 	has anyone defined a way to do QoS-aware IP over ATM?

There are several ideas out there for doing this. One was to map RSVP QoS
parameters into ATM QoS, but I don't know offhand just how far that got. RSVP,
the IETF's attempt at making packet-switched IP behave a lot like a virtual
circuit-based network, might not be the last word in this struggle. You might
want to look up Multi Protocol Label Switching (MPLS) to see what QoS concepts
might be incorporated into IP credibly.

> By this I mean:
>
> 	(1) my UDP/TCP applications have certain QoS requirements;

They do? And how are these QoS requirements stated in UDP or TCP? Are you
using something non-standard? Are you postulating some sort of TOS parameters
in the IP frames?

> 	(2) my physical network has certain (dynamic) QoS constraints;
>
> 	(3) some of my network runs IP over ATM always,
> 	some of it runs IP over non-ATM lower layers always,
> 	some of it is capable of being configured dynamically
> 		to switch either packets or virtual circuits;
>
> 	(4) how do I go about call setup?
>
> I can reasonably demand that any applications with specific QoS
> requirements (i.e., requirements that cannot be deduced simply
> by inspecting the packet headers to determine the protocols in use)
> must use RSVP (or some other standard interface) to negotiate QoS.

The problem is that with IP today, you pretty much can't achieve what you
want. Even if you happen to have RSVP in your LAN, the majority of routers
you'll be traversing won't support it, the routing algorithms don't know to
search out routes based on QoS, and so forth. In other words, if you need QoS
for real, IP is not the answer right now.

> My ATM network control and physical link MAC must be performed in the
> gateway between my LAN and any WANs to which it may be attached.
>
> Any pointers to relevant references would be greatly appreciated.

My suggestion would be to look at sources describing MPLS. That seems to be
the most recent work of this nature for IP networks. LANE, RFC 2225, MPOA,
and all of these layered IP over ATM schemes pretty much ignore QoS, because
that's what IP does. For now.

Bert
manfredi@arl.bna.boeing.com

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