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DLSw+ Design Topologies 519
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You need to consider the number of remote-site routers peering to the central site. More
remote-site routers might necessitate more central-site routers to alleviate the processing
burden on the central-site router. More remote peers means more central-site routers.
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If connection requests are initiated from remote peers, that should not be a problem.
However, if they are initiated from the central site, that could be a problem due to the
amount of CPU usage needed to generate a session.
·
The types of explorers, whether they be NetBIOS or SNA, can affect performance.
Peering Router Placement
As soon as you have determined the number of DLSw+ routers, you need to determine their
placement. Peer placement usually depends on a combination of traffic load, multiprotocol
traffic volumes, backup scenarios, and encapsulation types. Let's take a look at four typical
methods to peer the routers:
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All-in-one (DLSw+, IP, and WAN)--Peer all remote routers to the central site, as shown
in Figure 14-7. The central site typically has a 7500 or 7200 router with a CIP card
installed and directly attached to a mainframe. In this situation, the router performs
several functions:
-- WAN encapsulations with the serial port connected to the WAN. Other functions
performed by the router include DLSw+ signaling to the remote sites and
communication with the mainframe. This is a solution for small SNA networks--
30 to 60 branches maximum. Because this solution represents the fewest
components, it is also the least-costly solution.
Figure 14-7
All-in-One
Cloud
Cental site
IBM S/370
DLSw+
DLSw+
7500 or 7200 router with
CIP
Supports 30Р60 branches
DLSw+
87200333.book Page 519 Wednesday, August 22, 2001 1:41 PM