Re: [Autoconf] Autoconf addressing model

"Charles E. Perkins" <charles.perkins@earthlink.net> Tue, 03 March 2009 21:30 UTC

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Date: Tue, 03 Mar 2009 13:30:35 -0800
From: "Charles E. Perkins" <charles.perkins@earthlink.net>
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To: Alexandru Petrescu <alexandru.petrescu@gmail.com>
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Subject: Re: [Autoconf] Autoconf addressing model
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Hello Alex,

Alexandru Petrescu wrote:
>
> -I find it more advantageous to describe stable subnets, with prefixes
>  (between /48 and /64) exchanged around, rather than /128s.

That's fine, as long as the destination is addressable within
a subnet.  If the destination does not live on a subnet, why
not use a host route (i.e., /128 address)?

> -I would avoid the assumption that an ad-hoc router maintains a
>  stable IP address while moving around.

Then you will have trouble.  There is no free lunch.
Either:
(a) the IP address stays the same, and the routes change, or
(b) the IP address changes, and there is a resolver to
      associate the IP address with some other identifier.

Since the design of the resolver in (b) is an unknown and
arguably much more difficult, I'll take (a) with a great
sigh of relief.


>
>
> The churning aspect of host-based routes was just one argument against
> /128s and finally against loopback/virtual interfaces.

Are the other arguments easily summarized in a few words?

>
> Of course, host-based routes could work in some networks, mainly
> depending on their size and way of moving.

This is true.  I don't see what's wrong with it.

>
> BEcause we simply don't know the size of the network in which they could
> work.  And that apparently it is avoided to put any limit on size of any
> kind.

Who said we had to avoid size limits?

>
> Even approximative evaluations of the size of the network in which these
> host-based routes would work aren't preferred by many.

I must have missed that, sorry.  Those "many" didn't often assert
their preferences in the [manet] working group.

>
>>
>> This magically "forgets" the last 10 years of development for ad hoc 
>> networking protocols.  Do you think this work was somehow invalid? 
>> Solving the problems you mentioned was, after all, the entire point 
>> of the work.
>
> Sorry for having sounded neglecting the results of ad-hoc networking
> protocols.  It was not the intention.  I believe some protocols could be
> used to propagate prefixes - instead of /128s - and may be more
> efficient, grow the network larger.

Well, to me it did sound very negative.  Moreover, I think it is just
fine to pass around subnet prefixes, if you have subnets.



Regards,
Charlie P.