Re: Ethernet / Unix Rwhod

Steve Deering (deering@su-pescadero.ARPA)
24 Feb 1986 14:35-PST

> I have often wondered if the problem might be better solved using
> "multicast" ethernet addresses. This way only sites which care about
> the information ever see it on the host end of the ethernet.
> The problem is specifying how to map IP addresses into outgoing
> ethernet multicasts.

See RFC966 for a proposal for IP multicasting. I am planning to publish,
sometime soon, a complete specification and report on our implementation

I believe ALL use of broadcast should be replaced by multicast. Ethernet
and all flavours of IEEE 802.2 networks support the proper addressing mode,
and interfaces that provide adequate multicast filtering are available,
so that we can now obtain the benefits of cheap multidestination (and
unknown destination) delivery without interrupting every machine on a

If it didn't mean changing the whole world, I would advocate changing
ARP to use a multicast address. Currently, when we want to use the
Internet protocols on our workstations, we must listen to the broadcast
address just so we can hear ARPs. That opens us up to all the other
broadcast junk that flies around the Stanford subnets (UNIX rwho packets,
PUP routing updates, Sun ND boot requests, XNS broadcasts, Chaos
broadcasts, DecNet diagnostic packets, etc., etc.) In this kind of
environment, there is no type of packet that EVERYONE wants to hear.

                                                -- Steve Deering

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