Subject: IBM 6611 TRN T1 Timer

From: "jim (j.) cobban" <[email-masked]>
Date: Thu, 7 Sep 1995 13:29:00 -0400

We have encountered an interoperability problem with the IBM 6611.  This
APPN implementation does not provide any mechanism for altering the value of
the reply timer (T1) on a LAN interface.  This is a reasonable shotcut to
take if you assume that merely because a device is reachable across a LAN it
is therefore able to respond quickly, but it is a false assumption.  If the
remote APPN node is actually located across a WAN network with multiple hops
then it is not possible to guarantee that an XID response can be returned in
less than 2 seconds.  This applies to many products on the market, in
particular to the case where the link connection to the remote node passes
through an IP network through DLSw gateways.

You might argue that all that is necessary is to connect the DLSw on the 6611
directly to the IP network.  However this will cause scalability problems,
which we are still trying to resolve in the RIG.  In the interim the network
can only be scaled by partitioning it using LAN connections.  The more
specific issue for Nortel is that we are not using IP on our WAN network, and
therefore the ONLY way that we can attach a 6611 to the network is across a
LAN connection.

I feel that this is a serious deficiency of the 6611, and I request that IBM
take steps to fix it as soon as possible.

Jim Cobban   |  [email-masked]                        |  Phone: (613) 763-8013
BNR Ltd.     |  bnrgate.bnr.ca!bcars153!jcobban       |  FAX:   (613) 763-5199
|                                                                             |
|   The opinions expressed are those of the author and do not necessarily     |
|   represent the opinions of Bell-Northern Research or Northern Telecom.     |