who gets a /32 [Re: IPV6 renumbering painless?]

Fri Nov 19 11:33:27 UTC 2004

On 19-nov-04, at 5:38, Stephen Sprunk wrote:

> According to multi6, you will get PA space from each of your ISPs and 
> overlay a prefix from each on every subnet.  I'll save y'all another 
> rant on the workability of that model...

> Some fear that you would more likely just generate a ULA, use that 
> internally, and NAT at the borders.

It isn't contrary to multi6 gospel to have the address swapping be done 
by boxes somewhere in the middle rather than have all hosts do it for 
themselves.

In other words, you get the advantage of NAT: you only have to 
implement multiple addresses in a few places, along with the advantages 
of no NAT: the process is reversed at the other end so protocols that 
break NAT assumptions keep working.

Note that at this time the main focus of the IETF multi6 working group 
is taking regular communication (such as a TCP session between PA 
addresses at both ends) and then repair outages using additional PA 
addresses.

Another way to do this is to use non-routable addresses (such as unique 
site locals) as the addresses that transport protocols such as TCP and 
applications see, and start remapping those to/from PA addresses from 
the start. However, this isn't backward compatible and it's more 
complex so we're not focussing on this approach at this time. I'm 
pretty confident that we can add this as an additional option later, 
though.