What is Enterprise Extender?

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

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

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

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

• Preserve investments in SNA applications
• Transport of SNA traffic in the IP network
• Connection with trading partners through SNA Network Interconnect (SNI)

For an installation, the remote branch offices must have an SNA-based server, and the SNA software on the server can be any of the 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 a mainframe host
• IBM Personal Communications (PCOM) for Windows
• Microsoft Host Integration Server (HIS) 2004

The initial step is to decide which platform will be used at the edge of the IP backbone and the SNA branch. Deploying the Enterprise Extender with Cisco routers does not require any additional hardware or software in the branch office. On the other hand, for server-side EE implementation, a standard IP router must be installed at the branch office, and in some cases, the SNA server software may need to be upgraded.

If a device or application cannot be migrated to TCP/IP, deploying SNASw or Enterprise Extender at the branch level is the next feasible solution to reduce the complexity of the environment.

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