Subject: updated question on spanning tree and DLS

From: [email-masked]
Date: Fri, 30 Jul 93 10:38:48 -0400

Sorry about that last question - I forgot that the traffic could get there
through the back door (R2-remote bridge-R1-DLSw1) in both cases.

However, it seems that SDLC to SDLC connectivity (the subject of another
siglet) could not be provided by the DLSw nodes in this environment because
the link between the DLSw nodes would normally be blocked.

It seems that if the DLSw participates in spanning tree, deploying DLSw nodes
in parallel with remote bridges would result in the links between the DLSw
nodes only being used as standby paths that could handle the SNA traffic in
the event the remote bridges went out of service.  The only normal function
that would be provided by the DLSw nodes in this environment would be to
provide local SDLC to LLC2 protocol conversion.

Is this correct?  If so, it seems like quite a drawback.

---

From: Choon Lee <[email-masked]>
Date: Mon, 2 Aug 1993 10:00:13 -0700

>> Is this correct?  If so, it seems like quite a drawback.

Norman,

Thanks for bringing up SDLC connectivity.
Yes, spanning tree protocol deals with bridged traffic, and SDLC traffic is 
not bridgable per se, a SDLC to LLC2 conversation box seems like a good thing
to have (since the conversion is not part of DLSw).

HOWEVER, when and if SDLC becomes supported, one can conceivably forwards
the tunnelled SDLC traffic (since SDLC devices are always locally attached to
a DLSw node) on a BLOCKED DLSw link (because now the tunnelled packet appears
as a routed rather than a bridges packet), and not get into loop situation? 
Comments?

Regards,
Choon Lee
3Com Corp