iSeries SNA Software Support Continues with Enterprise Extender

by Timothy Prickett Morgan

Two weeks ago, I told you about how IBM was winding down support for adapters that do not use TCP/IP networking as their core means of interconnection, including twinax adapters for linking dumb tubes and PCs to AS/400 and iSeries computers and various networking cards that support Systems Network Architecture (SNA) traffic. Because this is the kind of thing that makes people jumpy, I printed the entire announcement in the newsletter to avoid confusion. As it turns out, this was only half the story.

You see, while IBM is most definitely killing twinax adapters and networking cards that support its SNA protocol (including both Token Ring and Ethernet cards), IBM does have a plan for supporting SNA software protocols going forward with i5/OS for those customers who rely on the SNA protocol as a means of linking their applications to each other and their end users to those applications. While this SNA support, which will be available through a new software package called Enterprise Extender, does not provide 100 percent of the functionality within the SNA features of OS/400, it should provide enough software functionality to keep users from having to rewrite their RPG and COBOL applications to use the TCP/IP protocol.

I know what you are thinking. Didn't IBM already provide this functionality a decade ago with the AnyNet features it embedded into MVS, OS/2, AIX, and OS/400 and provided for Windows platforms as an add-on? Well, yes and no.

Without getting into all the gory details of AnyNet, the AnyNet products were initially a means of allowing SNA networks to support other protocols, such as TCP/IP, DECnet, NetBIOS, IPX, and so forth, so existing corporate SNA networks and the applications behind them running on mainframe and OS/400 servers could communicate with minicomputers, PCs, workstations, and other devices (such as ATMs and other specialized gear). The initial AnyNet products also allowed the Logical Unit 6.2 (LU 6.2) portion of SNA's Advanced Peer-to-Peer Communications (APPC) protocol to run over TCP/IP networks. AnyNet made its debut for the VTAM communication module for MVS on the mainframe in June 1994. AIX got support in July 1994, and AnyNet was available in OS/400 V3R1 in December 1994. OS/2 got its initial AnyNet support at the same time. Over the years, AnyNet's functionality was extended to allow more SNA functionality to be supported over other networks, and to allow the functionality of other networks to co-exist with SNA. But AnyNet was not perfect. Certain kinds of SNA traffic--such as dependent LU communications such as 3270 terminals and emulators linking directly to mainframe hosts--were never part of AnyNet, for instance. Moreover, the performance penalty for using AnyNet was often quite high because of all the protocol conversions. Like my father-in-law when he was a teenager working in a grocery store in Queens, who was referred to as "Diversified Morgan" by his boss, AnyNet "does everything, does nothing well."

Several years later, IBM's mainframe group and the APPN Implementer's Workshop, a group of companies and users with SNA needs, created an alternative and industry-standard way of allowing SNA traffic to work over IP networks, and the product that came out of this standard was called Enterprise Extender. In 1999, network equipment maker Cisco Systems announced it would support Enterprise Extender in its routers. Since that time, Enterprise Extender has gained support among mainframe users and software vendors, and in October 2004, IBM released a statement of direction that said that it would bring Enterprise Extender support to a future version of i5/OS. (You can read that SOD at by clicking here.)

With Enterprise Extender, IBM is grabbing its High Performance Routing (HPR) software, which takes SNA traffic, encapsulates it, and then sends it over the UDP, not the TCP/IP, protocol. (Funnily enough, UDP stands for Unreliable Data Protocol.) With Enterprise Extender, IBM is using UDP because it is a more reliable frame passing technology and because it is compatible with IP networks, to encapsulate the SNA. This results in better performance than AnyNet as well as more reliable performance and availability, and say sources at IBM, it is easier to set up and support than AnyNet, too. Perhaps most significantly, Enterprise Extender can support dependent LU links, like terminals and terminal emulator linked directly to hosts, which AnyNet did not. Also, SNA's Alerts, which is akin to the Simple Network Manage Protocol (SNMP) in TCP/IP, is also supported in Enterprise Extender. However, remote workstation controllers--such as 5294s, 5394s, and 5494s in the iSeries world--are not supported with Enterprise Extender.

The zSeries team has already warned mainframe shops that AnyNet is going to be unplugged from z/OS at some future point and replaced by Enterprise Extender, and while IBM did not make this clear in its statement of direction, the company is creating an iSeries-specific implementation of Enterprise Extender with exactly the same goal in mind--providing a better means of sending SNA traffic over IP networks. The important thing, say these sources, is that AnyNet and Enterprise Extender support, which is coming in a future i5/OS release--it could be i5/OS V5R4, it could be V5R5, it could be V6 for all we know--will overlap for a while, allowing for a smooth migration. Sources say that IBM has not decided yet if Enterprise Extender will be part of i5/OS or a separate licensed program product with its own fee, but what is known is that it will be tightly integrated into i5/OS such that most SNA applications that are running today will run without modifications, and those that do need modifications will involve changes to network settings, not application code.

By the way, IBM is not merely porting the z/OS code to i5/OS to bring Enterprise Extender functionality to the iSeries, but is doing an implementation from scratch so it can be more tightly integrated and yield the best performance. (IBM apparently looked at doing a simple port and decided that performance would not be good enough and integration would be less than adequate. IBM also figured that porting would, in fact, be more difficult than just doing it from scratch.)

To help customers plan for Enterprise Extender, IBM has just released a document that suggests how they transition from SNA to Enterprise Extender or to TCP/IP proper. That document is called "iSeries Upgrade Planning: Suggest Alternatives for WAN, LAN, Token Ring, and Twinax". While this document provides some planning options, what it doesn't really do is tell you what is going on with AnyNet and Enterprise Extender. Which is why I still have a job.

RELATED STORY

Rochester Winds Down Non-TCP/IP Networking on the iSeries