Enterprise Extender implementation

The best candidate for Enterprise Extender is an enterprise that has SNA applications in remote branches.

As discussed elsewhere, the motivation to migrate an SNA network to Enterprise Extender is:

To carry SNA traffic on the IP network
To preserve the investment in SNA applications
To connect to business partners using SNA network interconnect (SNI)

Two topologies that can be considered as candidates for migration to Enterprise Extender are the following:

Organizations that still use the older SNA technology with communication lines from the branch to an IBM communication controller
Installations that converted their SNA network to DLSw and use an IP backbone that consolidates the IP and SNA protocols

Migration of remote branches from the older SNA-based technology

an installation must have an SNA-based server in the branch. The SNA software on the server can be one of the following:

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

You can also use Cisco Routers with the SNA Switching Services feature (SNASw) loaded and configured.

The first step is to decide which platform to use at the edge of the IP backbone and the branch. The two options to implement Enterprise Extender on the SNA-based server or to use Cisco routers with SNA Switching Services (SNASw).

Implementing Enterprise Extender with Cisco routers does not require any additional software or hardware in the branch. If the decision is to implement Enterprise Extender on the server, a vanilla IP router is installed in the branch, and in some cases, an upgrade of the SNA server software is required.

Figure 1 depicts the Enterprise Extender network.

Figure 1. Overview of branch extender node connection from branch to z/OS

This figure shows the end-to-end Enterprise Extender flow. The RTP endpoint is within HPR. The HPR packet is integrated into a UDP packet and travels through the IP WAN routers to the data center, through the OSA-E card (which has a unique IP interface address), into the TCP/IP stack Enterprise Extender VIPA, then into the Enterprise Extender VTAM link (IUTSAMEH), and finally to the application.

Migration of remote branches from a DLSw/IP-based backbone

solution for transporting SNA data over an IP network, many organizations still have DLSw deployed in the WAN. Typically, you see DLSw used to transport SNA sessions over the WAN, with DLSw and SNASw routers deployed in the host data centers to distribute the SNA session to the host LPAR. The DLSw and SNASw feature code sets may be configured on the same data center router.

It is likely that organizations have a combination of both solutions for a while, because it takes time and money to migrate from DLSw routers to SNASw.

If an application or device is unable to be converted to TCP/IP, reducing the complexity of the environment by implementing SNASw / Enterprise Extender at the branch level is the next best option.

Figure 2 illustrates a DLSw and Enterprise Extender combined solution.

Figure 2. Remote branch connection to z/OS using DLSw and Enterprise Extender