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.This means that a PU2.0 station can connect to the host through any one of thetwo FEPs.If one FEP fails, PU2.0 stations can access the host via the other FEP.In addition to the Token-Ring-attached devices (approximately 15 per regional office), the two FEPs alsorun NCP Packet-Switching Interface (NPSI), supporting over 200 remotely attached devices via thepublic X.25 network.The total number of LUs supported per regional office is approximately 1800, with1500 active LU-LU sessions at any one time.The estimated traffic rate is 15 transactions per second.The first migration step is to implement Cisco CIP routers at one of the data centers, replacing thechannel-attached FEPs.A remote router is then installed in one of the regional offices.The two routersare connected using DLSw+, as shown in Figure 6-23.Figure 6-23: Subarea to APPN migration---phase one.http://www.cisco.com/cpress/cc/td/cpress/ccie/ndcs798/nd2006.htm (43 of 59) [9/16/2000 5:06:44 PM] Designing APPN InternetworksAs Figure 6-23 shows, the FEPs at the regional office continue to provide boundary functions to theToken Ring and X.25-attached devices.The two DLSw+ routers handle the traffic between the FEP atData Center 1 and the FEP at the regional office.SNA COS is preserved in this environment.After stability of the routers is ensured, the network designer proceeds to the next phase.As Figure 6-24shows, this phase involves installation of a second router in Data Center 2 and the regional office.At thispoint, FEP-to-FEP communications between regional offices and data centers are handled by the routersvia DLSw+.Figure 6-24: Subarea to APPN migration---phase two.http://www.cisco.com/cpress/cc/td/cpress/ccie/ndcs798/nd2006.htm (44 of 59) [9/16/2000 5:06:44 PM] Designing APPN InternetworksContinuing with the migration plan, the network designer's next step is to install an additional CIP routerin each data center to support traffic between the two data centers.As shown in Figure 6-25, the linksthat are connecting the FEPs in Data Center 1 and Data Center 2 are moved one by one to the routers.Figure 6-25: Subarea to APPN migration---phase three.http://www.cisco.com/cpress/cc/td/cpress/ccie/ndcs798/nd2006.htm (45 of 59) [9/16/2000 5:06:44 PM] Designing APPN InternetworksAPPN will be enabled to support the traffic between Data Center 1 and Data Center 2.Eventually, theFEP-based network will become a router-based network.The NCR Comten processors will becomeobsolete.Two of the NCR Comten processors will be kept to provide SNI support to externalorganizations.Figure 6-26 illustrates the new router-based network.Figure 6-26: Subarea to APPN migration---phase four.The communication links that formerly connected the FEPs in the two data centers are now moved to therouters.The FEPs at the data centers can be eliminated.The FEPs at the regional offices are merelyproviding the boundary functions for dependent LU devices, thus allowing SNA COS to be maintained.The next phase is to migrate the SNA boundary functions support from the FEP to the remote router atthe regional office by enabling APPN and DLUR.After this is complete, all the FEPs can be eliminated.The next step is to migrate from DLSw+ to APPN between the data center routers and the regional officerouters.This is done region by region until stability of the network is ensured.As shown in Figure 6-27,DLUR is enabled to support the dependent PU devices in the regional offices.X.25 attached dependentPU2.0 devices that are formerly connected to the FEPs using NPSI are supported via Qualified LogicalLink Control (QLLC) in the router.QLLC is the standard for SNA encapsulation for X.25.Figure 6-27: Subarea to APPN migration---phase five.http://www.cisco.com/cpress/cc/td/cpress/ccie/ndcs798/nd2006.htm (46 of 59) [9/16/2000 5:06:44 PM] Designing APPN InternetworksExample of APPN/CIP in a Sysplex EnvironmentThis section examines APPN and the CIP routers in a Sysplex (system complex) environment.Itprovides an overview of the Sysplex environment and its relationship with APPN along with adescription of how to use the following three approaches to support the Sysplex environment:Sysplex with APPN Using Subarea Routing---Option OneSysplex Using Subarea/APPN Routing---Option TwoSysplex Using APPN Routing---Option ThreeIt also describes how APPN provides fault tolerance and load sharing capabilities in the data center.Sysplex OverviewSysplex provides a means to centrally operate and manage a group of multiple virtual storage (MVS)systems by coupling hardware elements and software services.Many data processing centers havemultiple MVS systems to support their business, and these systems often share data and applications.Sysplex is designed to provide a cost-effective solution to meet a company's expanding requirements byallowing MVS systems to be added and managed efficiently.A Sysplex environment consists of multiple 9672 CMOS processors, and each CMOS processor presentsa VTAM domain.The concept of multiprocessors introduces a problem.Today, users are accustomed tosingle images.For example, IMS (Information Management System) running on the mainframe canserve the entire organization on a single host image.With the multiprocessor concept, you would notwant to instruct User A to establish the session with IMS on System A and User B to establish thehttp://www.cisco.com/cpress/cc/td/cpress/ccie/ndcs798/nd2006.htm (47 of 59) [9/16/2000 5:06:44 PM] Designing APPN Internetworkssession with IMS on System B because IMS might run on either system.To resolve this, a function called generic resource was created.The generic resource function enablesmultiple application programs, which provide the same function, to be known and accessed by a singlegeneric name.This means that User A might sometimes get IMS on System A, and sometimes get IMSon System B
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