Re: A new spin on multihoming: multihoming classes.

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

On Thu, 6 Sep 2001, Iljitsch van Beijnum wrote:

> On Thu, 6 Sep 2001, Shane Kerr wrote:
> 
> > However, there is a need for network multihoming, which will probably
> > need to be solved as well.  But given that most of the growth of the
> > routing table seems to be end users desiring reliability and speed, I
> > think the network multihoming problem can wait.
> 
> It never hurts to give the subject some thought.
> 
> Many of the large networks would really like an 8k global routing table
> in IPv6. That means: no more than 8192 ISPs with a PA block of their own.
> (I'll be using IPv4 terminology.)
> 
> I think this is a reasonable number if we can enforce strict requirements
> on holding PA blocks. Avoiding renumbering can't be a reason for having a
> PA block any more, even if this requires millions of hosts to renumber
> when there is some change in connectivity. People will feel they're held
> hostage by their existing ISP unless renumbering becomes completely
> painless. I think the tools for the actual renumbering are there, but
> changing DNS entries for all these hosts might be a problem.

A6 is supposed to deal with this quickly and painlessly.

> 
> Then there are the enterprises that want to multihome at the network
> level. Obviously, giving those PI space would be impossible. So they would
> have to announce a /48 out of one ISP's PA block to other ISPs. The other
> ISPs will allow this, because it brings in cash. Small ISPs will be happy
> to receive the /48s at exchange points, because that saves them cash.
> However, we can expect some of the larger ISPs to filter the /48s because
> they have no incentive for carrying the more specific routes.
> 
> Still, as long as all of its other ISPs peer with the "primary" ISP (the
> one the enterprise got its addresses from), the enterprise will be
> reachable when the link to its primary ISP fails or that ISP's POP fails.
> Only when the entire primary ISP is wiped off the network, they'll be
> unreachable from networks that filter the /48s.
> 
> But in that case, they can still fall back to multi-address / host level
> multihoming.
> 
> Iljitsch van Beijnum
> 
> 
> 


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