Re: remote broadcasts


Steve Deering (deering@pescadero.stanford.edu)
8 Mar 1988 20:44-PST


Jon,

Concerning "remote broadcast" (also known as "directed broadcast"), you
wrote:

        I am quite aware of the dangers of such packets.
        One caused a broadcast storm on our ethernet effectively
        bring down the net. As far as I know there is no defence
        against one of these packets coming in from the Internet.

Could you explain in more detail what that one broadcast packet contained
that effectively brought down your network, and why the fact that it came
from another network was significant? I realize that there are lots of
bugs out there in the way hosts handle broadcasts (and multicasts), but
surely it's time to fix the bugs and make our hosts a little more robust
in the face of unwanted packets, rather than imposing arbitrary gateway
controls to protect the hosts from their own stupidity. As you observed,
multi-destination datagrams can be a valuable tool; rather than imposing
gateway controls, I suggest that the right defence is:

        1) Fix hosts to ignore (i.e., silently discard) packets that
           they are not equiped to handle properly.

        2) Insist on the use of multicast, rather than broadcast, so
           that unwanted packets can be ignored efficiently.

Steve Deering



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