From: miw@cc.uq.oz.au (Mark I. Williams)
Subject: Re: Proposal: OSI Addressing on AARnet
Organization: Prentice Centre, University of Queensland
Date: Mon, 7 Sep 1992 02:28:09 GMT

kre@cs.mu.oz.au (Robert Elz) writes:

>What matters is whether the routing is going to have to know that
>various different ICC's (or whatever those things up the left hand
>end) and the next bits beyond that are really all on the same cable.

>It would be nice to have just one "net number" per cable, rather
>than several.

Actually, I think this is one area where IP got it royally
screwed up. The assumption in the Berkeley IP code (but not in quite a
lot of other implementations) that host will have one address per
interface, and that all the addresses directly reachable on that cable
will start in the same way has caused no end of heartache and a lot of
cludging to get around it.

It might be nice to have one "net-number" per cable, but it isn't going
to happen, and let's not start making any assumptions that will make
things hard later.

>Certainly a host is going to need several nsap's, but those should
>really be all the same for the first 17 18 19 bytes or something,
>with just the last one or whatever providing all the nsap's that
>a particular host needs.

why? People might find it easy to remember a swag of numbers that are
virtually the same, but I thought computers could cope with differences
better than that. Seriously, though, I think this is wishful thinking.
Machines with simple network connection will tend to have few,
similar-looking NSAPS, and hosts that are connected to multiple networks
are going to have multiple, probably wildly differing NSAPS. That's
life, and it's why there are still jobs for networking hackers.

>| In fact, if the IETF are going to go dropping what most probably be
>| CLNP-incompatible protocols into their address space, shouldn't we be
>| avoiding those addresses like the plague?

>Assuming the IETF goes the CLNP route, which isn't certain by any means,
>I'd expect there will be immense pressure to stay ISO CLNP compatible.
>Perhaps mandate use of some options or something (ie: define a profile)
>but its not likely there will be anything incompatible changed - even
>though there are some people who would like to do that.  If anything,
>if changes are made, they're likely to be pushed through ISO as a CLNP
>revision (recall that CLNP comes form the US, and largely internet
>people, in any case).

What worries me more is that the IETF will go for something non-CLNP,
but use an ISO 8348/AD  address. Then we'll be really in strife
if we use their addresses, because any OSI hosts will have to have
live in a different address space. This is quite possible, as ISO is quite
happy to issue AFIs for use in non-OSI protocols. The IETF changes may
well be pushed through ISO as a CLNP revision, but it still means that
it would be years before the internet was OSI!

The point of my original posting was, however, not to wait. There is a
need for OSI protocols now, and it is technically feasible. If the IETF
solve their problems quickly, and we can use the numbers, then there
won't be many machines to change the addresses of. If they take ages,
then we can't afford to wait for them anyway. 

cheers,


--
Mark Williams         The University of Queensland       miw@cc.uq.edu.au
+61 7 36 54012   (w)  Prentice Centre
+61 7 36 54477  (fax) Qld 4072  Australia
Nullum magnum ingenium sine mixtura dementiae fuit.  -- Seneca
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