What is Enterprise Extender?

IBM's Enterprise Extender Technology (EE) is a simple set of extensions to the existing High Performance Routing (HPR) technology used for encapsulating SNA traffic over IP networks. It's a standard created by the Internet Engineering Task Force (IETF) and APPN Implementers' Workshop (AIW).

In this scenario the two backbone networks are SNA network and IP network. SNA network connects the SNA devices and the IP network connects IP devices (TCP clients and TN3270 clients). The EE devices are located on the border of IP and SNA network, connected on one side to IP network and on the other side to SNA network. On the SNA Clients' side special hardware and software converts the SNA packets to IP packets. The IP network appears to be a logical link to the SNA HPR network, on the other hand the SNA traffic appears to be the UDP datagrams to IP network. UDP datagrams provide multiplexing because they contain UDP port numbers, which makes EE packets distinguishable from other IP packets. Because of no error recovery or flow control features UDP has low overhead compared to TCP connection. The UDP datagrams are routed to IP backbone without any changes. The Rapid Transport Protocol (RTP) is a logical connection between two mainframes and it uses the IP network as an HPR link.

The Enterprise Extender views the IP network as an APPN (Advanced Peer to Peer Networking) connection network which enables dynamic establishment of a single one-hop HPR link to any host for which IP connectivity is enabled, provided that EE is implemented at the host. This allows the Routing process to be handled completely within IP.

What tips help you to make a smooth transition from SNA to EE?
Consolidating SNA network into IP Network is a challenging task. But there are strong motivations to migrate to EE:

• preserving the investments on SNA applications
• carrying SNA traffic in IP network
• connecting to business partners using SNA network interconnect (SNI)

For an installation the remote branches should have an SNA based server and the SNA software on the server can be of any following types:

• IBM Communications Server (CS) for Windows
• IBM Communications Server for Linux
• IBM Communications Server for AIX
• z/OS Communications Server with Enterprise Extender running on mainframe host
• IBM Personal Communications (PCOM) for Windows
• Microsoft Host Integration Server (HIS) 2004

The initial step is to decide on the platform to be used at the edge of the IP backbone and the SNA branch. For implementing Enterprise Extender with Cisco routers it's not required to have any additional hardware or software in the branch. On the other hand, for the implementation of EE on the server side, a vanilla IP router should be installed in the branch and in some cases the SNA server software might need to be upgraded.

If a device or an application is unable to be migrated to TCP/IP, implementing SNASw or Enterprise Extender at the branch level is the next feasible solution to reduce the complexity of the environment.

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