Re: IBM TCP.


David C. Plummer (DCP@QUABBIN.SCRC.Symbolics.COM)
Tue, 4 Aug 87 09:33 EDT


    Date: Mon 3 Aug 87 16:54:35-EDT
    From: Ken Rossman <sy.Ken@CU20B.COLUMBIA.EDU>

    We've had a reasonable amount of experience with medium to large DECnet
    networks here at Columbia. We have our own internal network, and we also
    connect to various other sites who also have their own DECnet networks.

    I am not sure how Ethernet addresses are administered (I was under the
    impression that one or more of the larger corporations plugging Ethernet
    divvy up the board addresses by board manufacturer). In any case, the
    first four bytes of a DECnet transformed Ethernet address are, by some
    "global allocation" method, preassigned to DEC as I understand it.

Sorry. Ethernet addresses are, in theory, assigned to hardware
manufacturers in 2^24 address chunks and the manufacturer is responsible
for administering its 2^24 addresses. DEC is "reassigning" the original
hardware Ethernet address to be a DEC-specific protocol-related hardware
address. That is not the intention of the Blue Book. DEC does not
"manufacture" Interlan, 3Com, Symbolics, TI, etc, hardware, yet the
hardware Ethernet addresses used would indicate DEC does.

        ...
    As for DECnet, ARP, and ethernet addresses, Ultrix handles this just fine.
    We just make sure that DECnet comes up before IP does, so that the ethernet
    address that ARP uses is the DECnet-transformed one. /Ken

That's not what I meant. What I meant was that ARP existed in time for
DECnet IV to use it, and that if DECnet used ARP instead of its current
algorithmic translation, (a) we could preserve globally unique
addresses, (b) you wouldn't have to worry about bringing up DECnet
before IP (or any other protocol), and (c) if somebody else goes against
the intention of the Blue Book we could still run DECnet and that other
protocol at the same time (since it wouldn't then require different
Ethernet addresses).



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