What to do with that SNA net


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IBM's SNA technology has endured for nearly 30 years thanks to its scalability, reliability and manageability. But with TCP/IP becoming the network protocol of choice, most SNA shops are now plotting their migration strategies.

These SNA shops are actually keeping their applications, but are changing their underlying network infrastructures, says Audrey Apfel, an analyst at Gartner Group.

"People are planning to take apart their dedicated SNA networks and have the traffic, in various forms, ride an IP network," she says.

Users will be running their SNA traffic over IP backbones via technologies such as Data Link Switching (DLSw) or tn3270 sessions, which allow SNA users on IP networks to access mainframe data.

There are plenty of financial incentives to making at least some sort of shift from SNA to IP.

Nevertheless, less than half of all SNA nets that were operating in 1990 have been replaced with IP nets, Apfel says.

Gartner predicts that over the next five years, users with SNA as their primary protocol will spend a total of 20% more than IP users on training staff, hardware and software purchases, and administration.

One company that actually has largely replaced its SNAnetwork with an IP one is United Parcel Service. UPS used to have a huge SNA and X.25 network supporting hundreds of thousands of end users.

In the early 1990s, UPS started building a multimillion-dollar frame relay network optimized for IP traffic and ran this network alongside the SNA net.

That setup proved to be too expensive, so UPS consolidated its networks largely on frame relay and IP, says Tom Ferro, telecommunications director for UPS.

As a result, the delivery company has improved its network cost-to-performance ratio by 25% and its overall network performance by 15%.

However, UPS still has some of the vestiges of its SNA network in place, including X.25 lines for connecting handheld devices to the corporate network.

UPS also still runs many of its 3270 and Advanced Peer-to-Peer Networking (APPN) applications over its frame relay backbone using DLSw, Ferro says. APPN is an advanced SNA technology that optimizes routing communications.

Another large SNA shop, MCI WorldCom, has also moved down the IP backbone path but still has SNA at the edges of its network.

This move has resulted in a 10% decrease in planned downtime for network applications, says Laurence Kung, a senior network manager for the carrier.

Currently, the network carries APPN traffic over DLSw, but the company has plans to use High Performance Routing (HPR) over IP.

HPR is the latest version of APPN, and it allows SNA nets to perform IP functions, such as dynamic routing failover.

Some users will find it necessary to retain a portion of their SNA networks just because they know their business partners rely on the technology, especially in fields such as finance and insurance.

BB&T, a Winston-Salem, N.C., bank holding company, is gradually eliminating its front-end processors and replacing them with Cisco IP router-based channel interface processors, says Dennis Breen, IT strategic planner for the firm.

BB&T has about 600 branch locations connected by IP and ATM but still uses DLSw to run SNA-based teller applications to its branches.

"We'll probably always have native SNA," Breen says.

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