multicast groups on ether (was: danger of bridges)


Mike Brescia (brescia@ccv.bbn.com)
03 Apr 87 11:52:45 EST (Fri)


     Do you have a concrete suggestion on how to manage the multicast group?

How about the following (summary: manage by czar).

The goal is to completely eliminate use of the broadcast address. TCP/IP
implementations may be overusing this feature, between ARP, RWHO, etc.

Go to the ethernet number czar and get two (2) groups of 65536 (2^^16)
multicast addresses. By that, I mean the high order 32 bits are assigned by
the czar, and the low 16 bits are ours to play with. Call the first group
<ether-link> and the second group <ip-port>. These become well know, and wired
in the programs, much like 255.255.255.255.255.255 is today.

The first group, <ether-link>, is the contact address for all hosts which
handle 'broadcast' for a particular ether link (message type). Thus ARP,
instead of polluting all the hosts in the net, would send to the address
<ether-link>.8.6 (0x0806 is the number assigned to the address resolution
protocol).

The second group, <ip-port> is the set of addresses for IP broadcast
protocols, and subdivided into one byte of IP protocol (e.g. UDP, 17), and one
byte of well-known-port (e.g. RWHO, 550 (oops, well, you get the idea).

While this idea is a bit half-baked, it should serve to move host and gateway
impementations to independence from broadcasts.



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