Robin@turbo.RAY.COM (Robin Alston) (04/30/88)
We have a bunch of SGI workstations currently running XNS over ethernet. We have just been informed that when we move into a new building at the end of May we will have to use a single ethernet cable for the whole building which includes many vaxen running VMS many many pc's with some kind of future-net link and many pc's with simple vax links. My question is can this really work? Can XNS and TCP-IP share the same coax cable with no possible problems? Can we have our own domain (we really have no interest at this time in talking to our vaxes), while decnet has its own on the same cable? Am I right to be paranoid about some bureaucrats decision to limit internal cabling this way? We are intending at some future time to upgrade to TCP-IP so we can run NFS but we want to do that in our own sweet time and not in a hurry. Any help or hard facts would be gratefully accepted before I go out and humanely shoot myself. -- ------------------------------------------------- # Whats worse than two MA drivers on a freeway? # Dr. Robin the REAL # Answer: One Toronto driver # SuperUser Atilla! ------------------------------------------------- (617)-460-8225 Robin@turbo.ray.com .....!rayssd!turbo!Robin
limes@sun.uucp (Greg Limes) (04/30/88)
In article <218@turbo.RAY.COM> Robin@turbo.RAY.COM (Robin Alston) writes: >Can XNS and TCP-IP share the same coax cable with no possible problems? No problem. At the bottem layer, all the packets are tagged with source and destination ethernet addresses, so packets only go where they are expected -- except for the broadcast packets ... Also, there is a field in the ethernet packet that determines the protocol type; this should be checked by your network software. Hopefully the drivers will not bitch about unknown packet types, as the XNS packets are a complete mystery to TCP, and TCP is just greek to XNS. It is even possible (gag) to run both TCP/IP and XNS through the same physical interface, but the bottom layer does need to know where to send each packet type. You might consider contacting someone at Communcation Machinery Corporation in Santa Barbara, California; when I was there we did some XNS development that shared the building-wide ethernet with normal TCP used by all the other iron. >Can we have our own domain (we really have no interest at this time in >talking to our vaxes), while decnet has its own on the same cable? You do not need to do anything special to ignore each other; in fact, quite a bit would need to be done to make them talk. One would have to understand the other's protocol. Imagine red and blue light in an optical fiber. The upper level packet layouts just do not jibe. -- Greg Limes [limes@sun.com] frames to /dev/fb -- Greg Limes [limes@sun.com] frames to /dev/fb
dls@mace.cc.purdue.edu (David L Stevens) (05/01/88)
We ran two distinct logical TCP/IP networks on one Ethernet cable for a time with no problems. The only thing you'll have to worry about are (Ethernet) broadcast packets, since those will go everywhere. IP should drop them quietly, but I don't know about XNS. -- +-DLS (dls@s.cc.purdue.edu)
davidsen@steinmetz.ge.com (William E. Davidsen Jr) (05/03/88)
You can put a LOT of still on one cable. The limiting factor is the
traffic, not the number of devices (until you reach the addressing
limit). I would not expect to see any trouble, and you can get software
for the VMS machines to enable sending SMTP mail to them.
--
bill davidsen (wedu@ge-crd.arpa)
{uunet | philabs | seismo}!steinmetz!crdos1!davidsen
"Stupidity, like virtue, is its own reward" -meron@topaz.rutgers.edu (Ron Natalie) (05/04/88)
XNS and TCP/IP will coexist on an Ethernet. They use different Ethernet Type numbers. I have the TCP/IP version of flight simulator when you're ready. -Ron
zemon@felix.UUCP (Art Zemon) (05/06/88)
Other people have given you the theoretical whys and
wherefores about doing this. I thought I would chip in some
practical experience in case you are the type who wants
"real proof". (I'm not trying to be derogatory here, just
helpful.)
We run one Ethernet cable with the following protocols on
it:
TCP/IP
XNS
DECnet
DEC LAT
DEC MOP
Everything runs just fine. Don't worry about it.
--
-- Art Zemon
By Computer: ...!hplabs!felix!zemon
By Air: Archer N33565
By Golly: moderator of comp.unix.ultrixegisin@watmath.waterloo.edu (Eric Gisin) (05/07/88)
One thing no-one has mentioned yet is the case where the ethernet type is a valid 802.3 packet length. I think Xerox PUP falls in to this catagory (what's PUP anyway?). What do 802.3 compatible systems do with such packets? VMS 4.4, for example, supports 802.3 LLC headers.
bob@cloud9.UUCP (Bob Toxen) (05/11/88)
You can run just about any protocl on the same ethernet cable.
This is because anyone wanting to devise a new protocol is supposed
to obtain a protocol number from Xerox. This protocol number is
encoded in the sent packet. Receivers are expected to recognize only
the protocols they are prepared to deal with. This is why this works.
--
Bob Toxen {ucbvax!ihnp4,harvard,cloud9!es}!anvil!cavu!bob
Stratus Computer, Marlboro, MA
Pilot to Copilot: What's a mountain goat doing way up here in a cloud bank?