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SDLC DLSW 1500 peers

We have a requested requirement to provide 1500 SDLC DSLW connections from 1500 remote locations to 1 data center. While attempting to scope out a router(s) type for the data center, we are trying to dig up what the potential limitation would be for the number of concurrent DSLW peers/sessions that a 7200 NPE-GE would be able to handle.

All SDLC connections would be at 9.6kb or lower.

What we have put together so far is to 7200 series routers to handle this load in a load balanced fashion, however if one fails it must be able to handle all 1500 connections.

Are there any specs available that provide limitations wihin this type of environment? If so, we are they?


Re: SDLC DLSW 1500 peers

The limitation is on the number of transaction, not the number of DLSw peer connections and DLSw circuits. Please go to the following URL for details:

As all SNA devices are on a slow link, I guess that you should be fine. Of course, I suggest you to estimate the transaction rate generated by the SNA devices.

The only concern I have is during the failover. I assume that you propose 2 routers in the data center. Each data centre router handles 750 peer connections. If one of the routers in the data centre fails, 750 routers will try to establish DLSw peer connections at the same time. The data centre router may not establish 750 DLSw peer connections at on e. (i.e. the recovery time may be longer than a couple of DLSw peer connections) Eventually, all DLSw peer connections and DLSw circuits will recovery. Not sure if your customer has any requirements on recovery time.

New Member

Re: SDLC DLSW 1500 peers

Somethings to consider:

SSCP-PU session(s) will need to be re-established during a failover. Are your DLSW circuits for

SNA PU T2.x or PU type 4? You could also predefine the dest macs with icanreach mac-address statements(DLSW reachability will be reduced to what macs you define and no curs). I remember reading a strong suggestion from Cisco stating both peer routers execute the same IOS level. 12.1.15 or higher resolves some DLSW TCP issues. Are you considering FST,DIRECT or TCP encapsulation? LLC2 local-ack default with TCP encapsulation. Will the DLSW routers connect to 37xx

IBM controllers? Duplicate Mac addresses defined on 37xx controllers? If each DLSW router has multiple T/R interfaces, you could enable dlsw duplicate-path-bias, see :

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