Re: Ethernet - Hyperchannel Gateway

Ralph A. Shaw (gatech!rayssd!rayssdb!
19 Oct 87 14:58:56 GMT

We at Raytheon have had some experience with the Hyperchannel
products, in particular the BC601, or EN601 as it is now known.
While I do not speak for the larger group of sites within the company,
I'll try and bring up some of the problems we think we have run into
with the EN601 product. This is merely using the Hyperchannel bus
as a carrier, and allowing ethernets to talk to each other, and is not
performing any type of gateway/protocol translation facility between
the TCP, DECNet, XNS or other protocol machines and the NETEX/BFX

We have a number of different locations scattered throughout Mass
and this site in RI that are interconnected via both A-Hyperchannel
and B-Hyperchannel equipment over T1 lines. Some of the locations
are tied together with Bridge GS3/M's, some with Vitalink Translan's,
some with the AT&T ISN "EBIM" adapters, and 5 locations with the
NSC EN601's, all presumably as part of an evaluation and/or production
installation, both of which add up to sites in at least 10 towns on
an extended ethernet; (total net population: 300+, 70% DECNet)

To make a long story short, many of the problems we have had have
been related to having such a widely spread out extended LAN. One
of the failings of the EN601 is the lack of visibility into what is
going on, in the way of maintenance and diagnostic aids as an ethernet
bridge, compared to the Bridge/Vitalink style of products. Another
problems may result in an inconsistency of loop detection algorithms
between the different vendors' bridges (while Bridge/Vitalink are
supposed to cooperate). Yet Another situation (which is still unclear
as to it's impact) is the fact that at least multicast packets are
batched up into a 4K buffer, and then VC-transferred to each other
EN601 in sequence, imposing quite a delay when the BFX traffic is
going on (making for very choppy telnet sessions).

Anyway, the 601's are still here, and NSC is supposedly working on the
problems we have with them, and they have improved them dramatically
in the time since we first got them in (we were an early Beta-test),
but I think that no matter what they do, the BC601 will always be
compromised by the fact it has to time-slice over the HyperChannel.

Ralph Shaw,
Raytheon Co.,		Submarine Signal Division
Portsmouth, RI		02871
ras@rayssd.RAY.COM  or	ihnp4!rayssd!ras

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