Re: Criteria for initial PA Allocation

[Adrian Bool <]

On Wednesday 23 May 2001 11:41, Matthew J Robinson wrote:
> It's by no means finished and I haven't done any more to it since last
> year.
>
> If we can get customers to adopt different methods of multihoming then we
> should be able to solve the problem. Otherwise we might as well accept that
> the routing table is going to explode :-(

I'm just think about routing table size - allowing customers to multi-home 
(and perferably load balance over both of their links) - and am not really 
worrying about IP space conservation.  ie. basically thinking in an IPv6 
world.

As with Matt's document, ISPs that want to provide multi-homed service from
co-operative pairs.  There is no reason why an ISP connect be a participant 
in multiple pairs.

When forming this relationship they go to RIPE and get a 'special' pair block 
of reasonable size - ie. large enough to fit a good number of potential 
customers.  It would be great if a very large block could be set aside for 
this purpose so that such blocks are easily recognised.

Both ISPs announce this block as a single route.  This route will naturally 
be seen on the Internet sourced from two ASs - is that so bad?  I can't think 
of it breaking BGP.

Customers who purchase a multi-homed service from these ISPs get allocated an 
IP range within this block.

Routing of the customer's block (which can be any size, but in an IPv6 world 
doesn't need to be that small...) can be done either by the ISPs statically 
routing to the customer or talking BGP to the customer with the customer using
a 'private AS' as with Matt's document.

The two ISPs advertise all more-specifc routes within this special block to 
each other - but no-one else.  Should one of the customer links fail any 
traffic that does go to the failed provider should be transfered to the other 
ISP for delivery.

As with everything, it has a few problems,

If the customer wants to change either provider they need to re-number - 
which is not nice.

It could be possible for ISP A to break, still announce the large special 
block and not have access to either the customer or ISP B - in which case ISP 
A could be blackholing the customer's data for some parts of the Internet - 
again not nice ;-(

Oh, yeah, it requires someone to use ipv6 ;-)

Regards,

aid




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