Re: Subnetting


braden@venera.isi.edu
Mon, 9 May 88 18:50:38 PDT


        It'll still seem useful, though, OK, maybe not essential for hosts to
        be able to find the subnet structure of a net. For sending directed
        broadcasts, suppose you want to say "broadcast on the net where host X lives"
        where X is known by name. It might be desirable to use the normal mechanism
        for finding X's address rather than hard-wiring an IP address into an
        application. In that case, since the domain name system doesn't (and shouldn't)
        record network structure, how could you find the right broadcast address?
        Admittedly this may stretch the point a bit but not too far, I think.

Stuart,

Directed broadcast is generally a poor idea (the right solution is the IP
multicasting). No architectural decision should be taken on the grounds
that it makes makes directed broadcasting easier.

        Likewise, if a host and several gateways are on some (sub)net, the host might
        want to set up its routing tables for a "good" choice of gateway to other
        subnets. Granting that routing should work if the host picks -some- gateway
        and depends on that to forward and/or redirect traffic as needed, it could
        still make good use of the information if it could get it.

I disagree. The Internet standard approach for a host: pick any
gateway and let it redirect you... is simple and effective. You REALLY
DON'T want hosts to know about routing, even subnet routing!!

Bob Braden



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