churti@greco.dit.upm.es (Francisco Gutierrez de Churtichaga) (04/26/91)
Hi everybody!!!
First, sorry for the previous posting, I had problems with the mailer..
We are in the process of designing a network that will serve as the backbone
of a number of Ethernets and TRs with diverse protocols that we have on site.
The backbone could be a TR Network or even a FDDI.
I have three questions regarding interoperability among TR and Ethernet/802.3
LANs:
1) Does the SRT bridging pseudostandard in fact allow interoperability
between a TR and a Ethernet END station or does it only provide the
means for sharing a internetwork structure (ie bridges)?.
2) Should the answer to the question above be negative (that is,communicating
TR end stations and Ethernet end stations across an SRT bridge is
impossible), what should be done to get this done?
3) Has anyone had experiences communications diverse environments across
an FDDI ring?. If so, what kind of equipment have you used?, have you
had problems integrating a concentrator, say from ATT and a CISCO
FDDI bridge using a Single Attach connection...Any comments regarding
these or similar matters would be very appreciated.
Thanks a lot !!!
______________________________________________________________________________
Francisco Gutierrez de Churtichaga. <churti@dit.upm.es>
Departamento de Ingenieria Telematica. Universidad Politecnica de Madrid. SPAINmitton@enet.dec.com (Dave Mitton) (05/22/91)
>From: churti@greco.dit.upm.es (Francisco Gutierrez de Churtichaga) >Newsgroups: comp.dcom.lans >Subject: TR,FDDI,Ethernet >Date: 25 Apr 91 19:17:15 GMT >Reply-To: churti@greco.UUCP (Francisco Gutierrez de Churtichaga) > >1) Does the SRT bridging pseudostandard in fact allow interoperability > between a TR and a Ethernet END station or does it only provide the > means for sharing a internetwork structure (ie bridges)?. SRT is a specification under development. It will become a standard when (or if) it is approved. It helps TR/Ethernet internetworking in that it propagates Transparent Bridging into the Token Ring environment, and removes the need for Source Routing support (both in code and wire overhead). However, SRT does not solve some the other TR to Ethernet interoperability problems, such as; bit order in MAC addresses, Functional Address to Multicast mapping, 802.2 to Ethernet frame format translation, or long packet segmentation. You have to evaluate the protocols on your LAN and whether _they_ support cross-media bridging. >2) Should the answer to the question above be negative (that is,communicating > TR end stations and Ethernet end stations across an SRT bridge is > impossible), what should be done to get this done? Communication is not impossible. There are just all of these problems that need to be avoided. It's conceivable to build a bridge that solves them, but so far every major token ring protocol implementation has blundered in some different way, and such a bridge will have a polyglut of protocol parsers and fixups. Typically protocol independance has been bridges primary feature that gains them their performance. The cynical consider Routers to be the only sane solution. >3) Has anyone had experiences communications diverse environments across > an FDDI ring?. If so, what kind of equipment have you used?, have you > had problems integrating a concentrator, say from ATT and a CISCO > FDDI bridge using a Single Attach connection...Any comments regarding > these or similar matters would be very appreciated. Digital produces an FDDI to Ethernet Bridge that you may want to look at. Dave Mitton, Token Ring Program Digital Equipment Corp.