Switching Grows Up: Prospects for ATM and Wrong Assumptions

Given their obvious benefits, nobody really doubts that Layer 3 switches will do well. ATM is the big question mark.

Until the recent emergence of gigabit Layer 3 switches, ATM was the only choice for upgrading core networks. And big risk-averse IT shops still see it as the safest bet - particularly if they are thinking about quality of service (QoS) and voice/data integration. QoS is embedded in ATM technology, and ATM is the telephone companies' preferred WAN solution.

In contrast, "Gigabit Ethernet hasn't really ramped up yet and won't have a solid QoS solution for several years," says John Armstrong, an industry analyst at Dataquest, Inc. in San Jose, Calif. "ATM is a much more mature technology."

But the best technology doesn't always win. Outside of FORE Systems, Inc., it isn't easy to find people who are bullish on ATM. Some say ATM has achieved a critical mass of adoption that will carry it forward, albeit with its growth checked by Gigabit Ethernet. Others are less optimistic.

"Despite record sales, ATM on the campus is doomed," asserts David Passmore, president of NetReference, Inc., a consultancy in Sterling, Va. LAN bandwidth is virtually free once the equipment has been installed because there are no ongoing line charges. Consequently, it makes more sense to over-provision the network than to mess around with QoS parameters.

"ATM had an opportunity and blew it," agrees Brendan Hannigan, an industry analyst with Forrester Research, Inc. in Cambridge, Mass. "It's too complex and too expensive."

Even committed ATM users are feeling beat up by all this negativity. When Chesapeake Energy Corp. in Oklahoma City decided to upgrade its core network with ATM last spring, network supervisor Bryan Sagebiel went to Interop in Las Vegas, eager to attend tutorials and learn more about the technology. But instructors, far from sharing his enthusiasm, were "kind of dogging ATM."

"I don't understand why," Sagebiel says. "I was skeptical at first. I figured, Ethernet is fine, so why spend the money? But since the migration, I think ATM's the greatest thing since sliced bread."

Infonetics Research, Inc. in San Jose, Calif., recently completed a study of users with high-speed LANs that suggests Sagebiel has plenty of company. The number of respondents using ATM doubled over a similar study conducted the previous year.

The respondents plan an average of 24 ATM backbone ports by 2000, amounting to 22% of their total. "So a lot more people are using ATM," says Mike McConnell, director of LAN programs for Infonetics.

Wrong assumptions

Industry pundits say a lot of ATM's problems stem from the fact that its original objectives are no longer valid. Bandwidth was assumed to be very expensive, so the idea was to micromanage it to squeeze out every drop. In a time of cheap bandwidth, this results in a lot of unnecessary effort and complexity.

ATM was based on the premise that it would go end to end, but it failed to get all the way to the desktop. Consequently, a lot of its services have little utility. Also, the mixed ATM/Ethernet environment results in segmentation and reassembly overhead that can't be tolerated in environments supporting compute-intensive applications such as imaging and simulation.

There also was a notion that fixed cell sizes were needed for switching to be efficient and cost-effective, but silicon advances changed the equation. "And frame switches are proving to be faster than cell switches, so ATM might yet lose out in the WAN," NetReference's Passmore says.

But a lot of the blame for ATM's bad reputation was earned in the early days, when users were struggling to implement first-generation technology.

"The older equipment used [permanent virtual circuits] instead of [switched virtual circuits]," says Richard Sweatt, director of marketing for Hitachi Internetworking, a division of Hitachi Computer Products America, Inc. in Santa Clara, Calif. Network managers had to run around manually configuring every desktop and endpoint. PVCs worked with Private Network-to-Network Interface's (PNNI) predecessor, the Interim-Interswitch Signaling Protocol. Administrators had to configure by hand each switch's address and the hierarchy of the switch interconnections - local address, group address and path to the backbone.

This didn't sit well with people who were used to broadcast LANs, in which you plug a device in and it automatically learns where everything is. The newer ATM equipment can do this as well, thanks to PNNI and other autoconfiguration features.

"You still have to do the LANE configurations and set the network up to run IP, but it's getting much better," says Hans Baartmans, a Unix network administrator at Texas Instruments, Inc. in Dallas, who has been working with ATM off and on for seven years.

3810 overview from FORE

Moves and changes are also very easy. "The FORE 3810 is the simplest system I've ever had to configure," Chesapeake Energy's Sagebiel says. "I plug the cards in, and it knows how to configure the VLAN. If I want to go from 155M to 622M bit/sec, I just change the cards and quadruple the bandwidth over the same fiber."

Chesapeake's mission-critical campus network has dual redundant paths to all the buildings. "You can't do this with Ethernet - spanning tree shuts one down," Sagebiel says. "But ATM inherently likes redundant paths and does load balancing across them. The failover of services is extremely fast."

The ATM camp is hoping there will be some price/performance improvements in the fourth generation of ATM switches that is being developed.

"There are more silicon vendors working on chipsets, so they should be cheaper," says Ashok Madanahalli, product-line manager for ATM internetworking products at FORE in Pittsburgh. "OC-3 to the desktop starts at $400 per port now. And Microsoft's Windows 98 is going to ship with FORE drivers."

That sounds like a lot to Ethernet users, but it's actually a bargain if you do the economic analysis right, says Phu Dang, manager of computing solutions for Shell Exploration & Production Technology Co. (EPTC) in Houston.

Shell EPTC installed a FORE ATM network a year and a half ago to support more than 400 engineers and scientists engaged in energy research. It has an OC-12 backbone and OC-3 to all of the Unix workstations and some of the PCs. PCs that can't support 155M have to make do with switched 100M bit/sec Ethernet instead.

"The hardware is only 20% of the total cost," Phu says. "Things like troubleshooting and upgrading - that's the real cost. If high-speed networking is essential to what you do, ATM is the obvious solution."

ATM's future on the LAN hinges on the changing application mix and price points. Basic business applications today don't justify the cost. But that equation could change if time-sensitive applications start to proliferate and ATM prices drop enough.

Whatever happens, ATM has made a major contribution to the art of computer networking. It has focused people on the problem of QoS and on the notion that the network needs to help applications more, not just transmit data.

To Part 3: Winners & Losers and The next Cisco?

Intro and What's in a Name | Over the horizon and Eliminating Layer 2?

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