Re: Subnetting


Stuart Levy (slevy@uc.msc.umn.edu)
Mon, 9 May 88 20:23:39 CDT


OK. If we have permission to squash systems sending subnet redirects
it'll make the situation easier. (At the University of Minnesota
we've had real operational problems with this in the past.)

And when we do have routing protocols that carry explicit subnet masks
I'll happily shut up.

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.

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.

Again, routing protocols designed for variable-sized subnets would let this
happen naturally.

        Stuart



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