Re: Many things on ethernet together???


Greg Limes (limes@Sun.COM)
Fri, 29 Apr 88 22:59:07 PDT


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



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