MCI's SNA to IP migration easier than expected

By Marc Songini
Network World, 5/4/98

Colorado Springs, Colo. - MCI Communications Corp.'s Glen Tindal has won a political and religious war - with no bloodshed.

Almost three years ago Tindal and his 15-member IS team embarked on a network crusade: convert the company's huge SNA backbone to TCP/IP. Network World first chronicled the MCI conversion in 1996 (NW, Oct. 7, 1996). The driving idea was to build an IP-routed backbone and move SNA to the edge of the new environment.

Specifically, the company's multimillion dollar InfoLink project moved MCI's 50,000 internal SNA users onto a TCP/IP backbone by eliminating more than 50 IBM 3745 front-end processors (FEP) and replacing them with 50 Cisco Systems, Inc. routers outfitted with Channel Interface Processors (CIP). The CIP routers obviate the need for FEPs by making it possible to link SNA hosts over a fully routed backbone.

When the project's financial impact is fully assessed, MCI says the company will have saved $16 million over three years - based on an investment of a little more than $5 million.

By dumping its FEPs, MCI is saving $3 million to $4 million annually in FEP maintenance costs. The cost of the upkeep for the Cisco routers and channel-attached cards is about $300,000 to $400,000, or one-tenth that of the FEPs, said Tindal, senior network architect at MCI.

Not only that, with IBM's help, MCI has sold all of its 3745s to other user companies, making a roughly $5 million profit.

Other savings are occurring as well. For example, MCI's FEPs were bound to a T-1 (1.544M bit/sec) line-speed restriction, Tindal said. The Cisco routers support T-3 line-speed (155M bit/sec) WAN links, which cuts latency by one-tenth of a second. Tindal estimates that improved access speed saves MCI $800,000 annually.

The new net backbone also lets MCI offer new services such as systems integration, consulting and SNA migration services.

"I would say looking back we knew we were taking on a real leading-edge project in terms of size and scale," Tindal said. "It was a challenge [because] the SNA people were never router jocks, and the router people never worked with [SNA] - we had a bipolar view of the world."

The decision to change from an SNA to IP backbone didn't happen overnight. Three years ago MCI had separate SNA and TCP/IP nets. The company gradually decided maintaining parallel nets was costing too much and was restricting employee access to corporate- wide MCI resources, Tindal said.

MCI's SNA environment was huge: 50,000 SNA users and 90,000 static SNA routes anchored by 25 IBM or Hitachi mainframes.

The net "was unwieldy in size, and the costs and administration were becoming prohibitive," he said.

As if moving to an IP backbone wasn't a big enough task, MCI also moved its traditional 3270-based SNA users to IBM's Advanced Peer-to-Peer Networking (APPN) technology to take advantage of improved performance and reduced administration qualities.

The components of MCI's new net read like an acronym-lover's paradise. At the central site, MCI installed the latest level of VTAM (Version 4.4) on the IBM mainframes. VTAM controls SNA communications.

The Cisco 7000 CIP routers run IOS 11.1. Together, VTAM and IOS support the technology necessary to run SNA and IP to the mainframe. That includes support for technology such as Cisco's Data Link Switching (DLS+) technology, which encapsulates SNA traffic in IP packets for transmission across the WAN.

APPN traffic at the mainframe site is handled via dependent LU Requester/Server technology (dLUR/dLUS). dLUR and dLUS work together to set up an APPN pipe across the backbone. The dLUS function only runs at the mainframe site.

The mainframes are divided in to two to six logical partitions (LPAR) per machine, and each LPAR has two Enterprise Systems Connections (ESCON) to the CIP routers - one for IP, the other for SNA. ESCON is IBM's fiber mainframe channel connectivity technology.

The CIP routers are connected via T-3 links to 13 aggregation centers scattered across the country. The aggregation sites typically house two Cisco routers, one to handle local LAN traffic, the other to handle local SNA/APPN data. The routers also support DLS+ and dLUR.

Ultimately, the new net backbone will enable MCI to make moves, adds and changes much more efficiently, Tindal said. InfoLink will also let the company better handle increasing IP traffic. Even SNA traffic has continued increasing, the company said.

MCI also thinks its network is a groundbreaker and the envy of the industry. "Many companies would like to do what we've done," said one MCI staffer. "We've set a precedent on what companies are able to do [when integrating SNA and TCP/IP]."