Re: TCP/IP and DECnet

John Sloan (cbosgd!wright!jsloan@ucbvax.Berkeley.EDU)
29 Sep 87 11:22:13 GMT

in article <>, melohn@SUN.COM (Bill Melohn) says:
> Technically speaking, DECservers do not speak DECnet, they use a DEC
> propriatary protocol called LAT. This is an ethernet protocol which
> coexists with any other Ethernet protocol (like TCP/IP) without any
> problems.

True, LAT terminal servers are nice with LAT-capable machines (like
VMS or Ultrix) but just about useless with any other vendors equipment,
which is why we're going to TCP/IP terminal servers. Anyway, I think
the issue here is whether the TCP/IP code and the DECnet code running
on the same machine can coexist on the same ethernet controller, which
is a very sticky question. The DECnet/Ultrix implementations seems to
work fine. We use DECnet to talk to the VMS machines, TCP/IP (and NFS)
to talk to the UNIX machines and our terminal servers, and LAT to talk
to the few LAT boxes in other departments. I remember reading, I think,
that other commercial products, like TWG's TCP/IP for VMS, would do the
same. But I would read the fine print very carefully.

I do know that there were a variety of changes to the networking code
in Ultrix to support DECnet. I seem to recall that the lowest level
TCP/IP layer was boosted up above an sort of generic ethernet packet
server that controlled the interface board, and handed out appropriate
ethernet packets to the TCP/IP or DECnet code.

John Sloan  CSNET: jsloan@CS.Wright.EDU	UUCP: ...!cbosgd!wright!jsloan
Computer Science Department, Wright State University, Dayton OH, 45435
+1 513 873 2491	  belong(opinions,jsloan). belong(opinions,_):-!,fail.
The only thing that depreciates	faster than a computer is fresh	fruit.

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