Gigabit Ethernet relieves ATM woes

Some users have breathed a resounding sigh of relief when they built Gigabit

Ethernet into their network backbones. Compared with building multiple protocols

on an Asynchronous Transfer Mode (ATM) network, it was a piece of cake.

The main issue with Gigabit Ethernet is not so much the upgrade itself

as the context into which it is upgraded.

Just two years ago, the Army's Information Systems Engineering Command

in Fort Huachuca, Ariz., wrestled with getting an earlier version of Ethernet

to work with its ATM network. The difficulty lay in the fact that ATM does

not understand the popular IP addressing on which Ethernet is based, making

it necessary to use local-area network emulation and addressing conversion

to trick ATM into running with Ethernet LANs.

"Our goal was to move IP packets from point A to B and cut the need

for conversion," said Dan Bradford, director of Fort Huachuca's Technology

Integration Center. "Here's why Gigabit Ethernet is winning: It moves IP

over Ethernet with no new addresses introduced."

This is one of the reasons Fort Huachuca chose Gigabit Ethernet over

IP instead of ATM when it came time to upgrade the network. Also, Ethernet

is an easy choice because it is ubiquitous within the Army. Every workstation

is equipped with an Ethernet network interface card. Plus, Microsoft applications

are IP-aware but not ATM-aware, Bradford noted.

Although ATM has been reliable for the Army, the technology was complex

and expensive, taxing operations and main-tenance. "ATM was a hornet's nest,"

said Bruce Adamson, network administrator at Fort Huachuca. "You just didn't

want to touch it if it was working. By contrast, Gigabit Ethernet has been

simple. The base uses Extreme Networks Inc.'s Summit 48 and Black Diamond

Gigabit Ethernet switches.

"Once we had everything set up and were ready to program the switches,

it took between 30 to 60 minutes to lay down the basic structure in the

Gigabit Ethernet switches," Adamson said. "All the switches have a management

point already on them. It was simply a matter of building the [virtual LANs],

assigning the ports and putting in the IP addresses."

Bradford pointed out yet another difference between ATM and Gigabit

Ethernet — security. "The access control lists of IP addresses you permit

or deny and the security features are more robust on Gigabit Ethernet devices

than on ATM devices," he said.