RE: Multihoming by IP Layer Address Rewriting (MILAR)

[Peter Tattam <peter@jazz-1.trumpet.com.au>]

On Wed, 5 Sep 2001, marcelo bagnulo wrote:

> 
> > > > > It doesn't tell the other end what addresses you might be coming
> from though.
> 
> > > > Good point. But this information could easily be carried in an IP
> option.
> 
> > > surprise surprise - that's what I'm proposing :)
> 
> > But you are proposing this in both directions, which is somewhat more
> > problematic: you can only send an IP option if you can send period... But
> > you could try each of the different addresses, of course.
> 
> If I understand it correctly this could be a good trade-off solution.
> 
> In a large portion of cases, a DNS query is performed before connection is
> established, so this could be a place where to include all the addresses of
> the target host, because no extra query is usually requiered.
> 
> However if we want to use DNS to obtain source host address set, this would
> requiere an extra DNS query which may not be desirable, so source address
> set can be carried in the IP prefix option.
> 
> In addition, the IP prefixes option could include a flag which indicates
> whether the source host has a target address host available (it got it from
> DNS) or not, so that the target host can include or not a IP prefix option
> in the SYN-ACK packet. This option could be included anyway to override the
> existent address set.
> 
> Regards, marcelo
> 
> 
> 

For the case where you only have a single starting address but there exists
several alternative addresses and there is no way to find the alternatives (no
DNS entries), you can only rely on routing infrastructure to tell you the rest
of the addresses if the peer can't tell you.  This case would force routers to
get involved which I hoped one could avoid.

It doesn't have to be a router that tells you this, just some third party
service like DNS or a reachability cache or somehing. 

I agree with the comments mad by Christian about DNS not being the best vehicle
for this kind of information. 

Is it worth pursuing the reachability cache idea?

Peter

--
Peter R. Tattam                            peter@trumpet.com
Managing Director,    Trumpet Software International Pty Ltd
Hobart, Australia,  Ph. +61-3-6245-0220,  Fax +61-3-62450210