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Path: utzoo!watmath!clyde!rutgers!mit-eddie!genrad!decvax!ucbvax!XX.LCS.MIT.EDU!ROMKEY
From: ROMKEY@XX.LCS.MIT.EDU.UUCP
Newsgroups: mod.protocols.tcp-ip
Subject: ARP, ethernet and starlan
Message-ID: <12276567612.70.ROMKEY@XX.LCS.MIT.EDU>
Date: Thu, 5-Feb-87 04:20:01 EST
Article-I.D.: XX.12276567612.70.ROMKEY
Posted: Thu Feb  5 04:20:01 1987
Date-Received: Sat, 7-Feb-87 11:08:54 EST
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 39
Approved: tcp-ip@sri-nic.arpa

Here's a definition of a phrase I will use in this message. I just
want to avoid any ambiguity at the onset:

Here's a problem:

Starlan is an 802.3 network; it looks like ethernet except it's cabled
differently, it runs at 1Mbps instead of 10Mbps and (I think but I'm not
certain) it's manchester encoding is slightly different.

I need to bring up TCP/IP on Starlan, and I have a question:

What ARP hardware type should I use?

My immediate reaction is to go to the number czar and ask him to assign a
starlan number and use that. But wait...there's a catch.

Some vendors have or are developing MAC-level bridges which connect ethernets
to starlans (as well as other ethernets). For this type of connection
to work correctly, Starlan must have the same ARP hardware type as ethernet
or else machines on one net connect to another via a MAC-level bridge will
discard ARP requests because they will be for the wrong hardware type
(I assume that we *do* check this field, after all...) and no communication
will occur.

Would the number czar care to comment?

Also, does anyone know if any vendors are planning to develop an 802.3
to 802.5 MAC-level bridge? Different waveforms and different speeds, I
know, but similar packet headers.  If they are, then we've already
lost because there is already an 802.5 ARP hardware type which is
different from ethernet.  Maybe there should be an 802.x ARP hardware
type...

John Romkey			FTP Software, Inc.
(617) 864-1711			PO Box 150
UUCP: romkey@mit-vax.UUCP	Kendall Square Branch
ARPA: romkey@xx.lcs.mit.edu	Boston, MA, 02142

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