Re: The state of IPv6 multihoming development

[Iljitsch van Beijnum <iljitsch@muada.com>]

On Wed, 23 Oct 2002, Tim Chown wrote:

> > One thing still remains clear though - multihoming is the thorn in the side for
> > IPv6.  Until it is finalized, IPv6 will be going nowhere.

> What proportion of Internet sites are multihomed?  Academia generally isn't,
> not to the universities, although the NRENs will have multiple peerings.

But they do often have PI space. How would universities like it if they
had to renumber every time their transit ISP changes?

This could be called "serial multihoming": an organization doesn't
actually multihome, but changes ISPs relatively frequently.

> What proportion of Internet enterprise sites are mission critical?

Business still send out bills through regular mail. At some point in the
future, they're going to realize this costs a lot of money and is very
inconvenient. When they start sending out bills over the net, suddenly
their connectivity becomes mission ciritical.

I'm not sure our billion multihomers is very realistic, but expecting we
can do IPv4-style multihoming and not run into trouble is a very big
risk.

Don't forget that in IPv4, lots of organizations can't effectively
multihome, because they can't get a large enough block of addresses and
small blocks are filtered. In IPv6, everyone gets a /48 so filtering on
prefix length doesn't work anymore and it's all or nothing.

> How frequently are multihomed sites calling on their resilient links?

When you have extra links, you usually load balance/traffic engineer
your traffic over them. See http://www.oreilly.com/catalog/bgp/chapter/ch06.html
on how to do this.  :-)

> How much of the IPv4 DFZ clutter is due to multihomed sites?

Actually not that much. There are less than 30k ASes, and around half of
them are visible in the global routing table. Of those, a fair number
must be ISPs.

Iljitsch