IBM frees users from master-slave strictures of SNA - Systems Network Architecture

Communications News, Dec, 1992 by Morris Edwards

As a tumultuous year for IBM comes to an end, Big Blue is well on its way to revamping completely its network computing strategy.

Gone is the hierarchical, master-slave stricture of SNA (systems network architecture). In its place: a peer-to-peer capability that allows desktop users to access and share information without host intervention.

This new capability is one part of a two-pronged strategy for IBM to compete in an era of multiprotocol networks and client-server computing. The second element is a new networking blueprint which provides a framework for integrating multivendor applications using different types of communications protocols into a single network.

Since the blueprint spans local area networks (LANs) as well as larger, wide area (WAN) and global networks, it affects networking decisions for all users--small, intermediate or large.

Blueprint for integration

IBM's blueprint covers four aspects of network integration. The first, multiprotocol routing, is handled by the IBM 6611 network processor, a multiprotocol bridge-router that can integrate different types of LANs with each other, or with WAN types such as X.25 and frame relay. In the past, separate networks were needed to support users of different protocols such as SNA, TCP/IP (transmission control protocol/internet protocol), IPX (internet packet exchange), AppleTalk and DECnet.

IBM's blueprint also addresses the evolution from today's to tomorrow's applications with both LANs and WANs, supporting current data rates measured in megabits per second as well as the gigabit speeds required by more advanced applications. For LANs, this means migrating from Ethernet, token ring and FDDI (fiber distributed data interface) at speeds to 100 Mb/s, to technologies such as fiber channel standard at gigabit speeds.

In WANs, it means evolving to fast packet and cell-based technologies that can also achieve gigabit speeds.

For multivendor application support, IBM provides a structure for extending the reach of many different types of applications throughout many networking environments, allowing users to more freely access and share information. This is done through a networking function called Common Transport Semantics, by which applications can access various transport services of the network.

Finally, IBM's blueprint includes systems and network management disciplines, such as problem, configuration, change and performance. Mainly, IBM will provide SNA management services, SNMP (simple network management protocol), and CMIP (common management information protocol).

In addition, IBM says the network management system will be provided within its System View framework.

Client-server agent

One of the keys to the new blueprint is a transport and routing protocol called APPN (advanced peer-to-peer networking). Because APPN permits direct communications between users anywhere on the network, it is IBM's answer for client-server computing. That's why IBM is pushing to support APPN on all its systems, with the last--and most important -- element being APPN for mainframes.

IBM will complete this significant feat with the imminent delivery of Advanced Communications Function/Virtual Telecommunications Access Method version 4 for MVS/ESA mainframe operating systems. ACS/VTAM 4.1 extends the range of IBM computers supporting APPN to IBM System/390 mainframes.

IBM also is licensing APPN network node specifications so that other vendors' products can be integrated with APPN networks. Novell was among the first to support APPN through its NetWare for SAA product line.

APPN is vital to IBM because it can handle distributed network functions, such as routing information without help from a host, yet can coexist with hierarchical SNA in the same network backbone. IBM claims there are 50,000 SNA networks in operation, so APPN is a critical migration path to network computing. Also, APPN keeps track of network topology, making it considerably easier to connect and reconfigure nodes.

IBM's networking goal is summed up by Don Haile, networking systems director for LANs: "(To help users) build their computer networks so that they can combine the productivity and ease-of-use of desktop applications with the data security and networking sophistication of mainframe-based computer centers."