Janto, it depends on your transaction rate and how your break up your logical functions. WIthout getting into specifics, your HQ location will most likely need WAN termination ,DLSW peering, SNASW, bridging and CIP functionality and perhaps IP summarization.
Here's a good paper on DLSW perfromance:
http://www.cisco.com/en/US/products/sw/iworksw/ps2474/products_white_paper09186a008007ce75.shtml
Gather your data:
You should figure out your transaction rate (3270 in/out) + other non-DLSW IP transactions and design around that. You will need to consider backup routers
and backup media paths.
Here's a similar design I used a few years ago for a customer that's still
working fine today:
MAINFRAME HOST X (5) w/multiple LPARS
|
ESCON DIRECTOR x (2)
|
7513's X (2) w/2 CIP's
|
| (Fast Ether or Token RIng)
|
7206 NPE200 X (6) - For DLSW Peer and SNASW Function
|
|
|
7206 VXR's NPE300 X (6) - (WAN Frame Relay Termination + IP summarization)
|
WAN Frame Relay
|
Field routers X (1000 sites) (DLSW peer + Frame Relay)
|
SNA PU type 2.x
The point I wanted to make is that the design was based on a measured
transaction rate. Based on this data, it was decided to break apart the functions. The CIP routers only handle the Channel protocols. We used a string of 7206 routers at HQ to handle only SNASW (DLUR) and DLSW.
We used another string of 7206's to handle WAN aggregation and IP summarization. We estimated that the 7206's at the DLSW level could handle up 300 - 400 sites based on transaction rate. The field routers point to a backup HQ DLSW peer router if the primary fails. SO, normally each HQ DLSW peer connects to less than 200 sites , but can connect to over 300 sites in backup mode.
As far as the CIP router goes, you may want to run ESCON to more than one Director if you use Directors.
Hope this helps.
Brian Kelley
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