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Hey, sports fans: scout virtual routers for your ATM team.

Unlike the National Football League, where teams thumb their noses at fans and then slink away to cities beckoning with bigger pots of gold, in networking the situation is reversed. We get teams coming into town to vie for the bigger-bandwidth loyalties of the Ethernet fans.

One player for the ATM team who might get those fans excited is MPOA (Multi-Protocol Over ATM), a standards set that makes possible a "virtual router" approach.

The result of work by a subgroup in the ATM Forum, MPOA allows Layer 3 network layer routing over ATM and enables companies to leverage ATM's benefits, including Quality of Service and data forwarding. It is done via direct switched virtual circuits to build manageable, enterprise-wide LAN internetworks.

MPOA offers a solution to some shortcomings of the LANE (LAN Emulation) specification. LANE, which lets legacy LANs communicate with ATM-attached hosts, can't run protocols in native mode and has problems with performance bottlenecks due to required router hops for virtual LAN interconnection. It also has some management problems resulting from flat Layer 2 network designs.

Argonne National Laboratory in Illinois has sampled MPOA since December. Paul Krystosek, computer network engineer with the Electronics and Computing Technologies Division, says early results show it's a step in the right direction.

The trial, with Newbridge Networks, involves about a dozen users along with a classroom with seven Sun workstations. The classroom is linked to a Newbridge Yellow Ridge Ethernet edge switch with an ATM interface.

"We have high-end users who have research or production needs for transferring large volumes of data across campus or across the country," Krystosek says.

Needs include scientific data collection that requires different Quality of Service data streams; multiple video streams that Argonne would like to multicast at a high data rate; and parallel applications, for which Krystosek says "we would like to have the same network architecture, whether it is machines sitting next to each other in a rack or distributed across the country."

Krystosek says multicasting in a LAN emulation environment doesn't perform to Argonne's satisfaction, and the differing Quality of Service data streams "is something we can't really do with LAN emulation at this point. We are hoping MPOA will do better and that native ATM will do better yet."

Argonne also wants better access to a pair of OC-3 external links, one to the Department of Energy ES (Energy Sciences) Net and the other to a regional (research network.

Krystosek says networking needs grew in surges at Argonne.

"What tends to happen is a new user or application changes the whole situation. Going back a few years, we had a very simple lab-wide system, with 1 Mb/s links into a big Ethernet bridge. Then the advent of X Windows prompted us to change it. That's where our lab-wide FDDI came from.

"There were people who wanted better access but couldn't afford FDDI, so we came up with the Hubnet, a collection of Ethernet hubs that go out to divisional routers. That is where we stand today."

In their efforts to stay ahead of users' needs, Krystosek says native ATM is appealing, but limiting. "If you have an existing application, it would be a major operation to port it. If you had an API (application programming interface) it would be straightforward, but you can't do some of these things in LAN emulation. What we need is something more versatile. We see MPOA as a better stepping stone to native ATM."

The ATM network backbone at Argonne will be a single Nortel Concorde, a central office-class switch. In the trial, Krystosek says, each solution will be evaluated by itself and then by how it integrates with the Concorde and the ATM-attached Cisco routers.

"Hopefully at some point the standards will be to the point that two integrated solutions can communicate directly. But once you cross a network boundary you are probably going to be limited by going through a router, at least for some time to come," Krystosek says.

Before making a recommendation later this year for the fiscal 1997 budget cycle, Krystosek says Argonne will check out other vendors' integrated offerings, preferring those with a migration path to MPOA.

Based on what he has seen so far of MPOA, "it is heading in the right direction. But there are a couple of things that would prevent us from putting what we have today into full production," says Krystosek.

He explains that in mixing integrated solutions that have multiple components, users sometimes are "restricted to a few least common denominators." They found some at

Argonne, "but we have discussed that with Newbridge, and this will be part of a future release."
COPYRIGHT 1996 Nelson Publishing
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Copyright 1996 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Technology Information; The Proving Ground; the Multi-Protocol Over ATM or MPOA standard
Author:Tanzillo, Kevin
Publication:Communications News
Article Type:Column
Date:Apr 1, 1996
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