Goodbye token ring, hello Ethernet

Making the move from token ring to Ethernet? If so, go as far as you can, as fast as you can.

That's the advice from Equitable Life Assurance Society's IT staff, which recently finished moving the company's service organisation from a shared 4/16Mbit/sec token ring environment to a switched 10/100Mbit/sec Ethernet network.

The company had been considering moving away from its 800-user token ring network for several years. The time seemed right when the company decided to upgrade its desktop and server platforms and consolidate its service organisation at a new site in Charlotte, North Carolina.

The migration project, which involved grouping three service centres into one, has cost the company more than $US1 million.

Given that the network can now speed traffic five to 50 times faster, Equitable figures the project will pay off in increased productivity and the ability to support expanded workflow and imaging applications.

Because it was moving to a new site, Equitable ditched most of its token ring gear, some of which was 10 years old and fully depreciated.

"Token ring has been fading because Ethernet is simpler, has higher bandwidth and has been less expensive to deliver," said Charles Sokolski, managing director of IT operations and infrastructure at Equitable. And besides, "we had a clean slate," he said.

Equitable received vendor proposals for its new network by the summer of 1997 and picked Cisco as its primary network equipment supplier that [US] autumn. The key device in the Equitable network is the Catalyst 5500 switch, which can be used in wiring closets and to anchor backbone networks. The Catalyst 5500 can also handle Ethernet and token ring traffic.

By May 1998, Equitable was installing desktop machines in Charlotte, and the company was able to start up its new network during two weekends in July.

The Charlotte network consists of 45 NT, OS/2 and Unix servers, 10 Catalyst 5500s and a pair of Cisco 7513 routers. Currently, there are about 150 token ring workstations on the network, which is home to more than 800 desktops servicing 650 users.

The company has experienced a few bugs translating between token ring and Ethernet traffic, but no "show stoppers", Sokolski said.

Traffic is transported between the 5500s using Cisco's Inter Switch Link (ISL) tagging protocol, which encapsulates Ethernet and token ring frames over Fast Ethernet. Frames can then be translated from Ethernet to token ring, or vice versa, by the 7513 routers.

"ISL is the key to a media-independent backbone -- one that simultaneously supports both token ring and Ethernet frames," said Frank Whitten, a Cisco product manager who worked on the Equitable project. "Since the technology is based on Ethernet, when Equitable is finished with its migration, it is left with an Ethernet backbone and uplinks."

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