[ppml] Soliciting comments: IPv4 to IPv6 fast migration

John Santos JOHN at egh.com
Fri Jul 27 16:44:24 EDT 2007

On Fri, 27 Jul 2007, Ted Mittelstaedt wrote:

> >-----Original Message-----
> >From: ppml-bounces at arin.net [mailto:ppml-bounces at arin.net]On Behalf Of
> >William Herrin
> >Sent: Friday, July 27, 2007 9:14 AM
> >To: Keith W. Hare
> >Cc: ppml at arin.net
> >Subject: Re: [ppml] Soliciting comments: IPv4 to IPv6 fast migration
> >
> >
> >On 7/27/07, Keith W. Hare <Keith at jcc.com> wrote:
> >> With some amount of push from customers and lawmakers, the telephone
> >> companies have moved from Provider Agregatable phone numbers to Provider
> >> Independent phone numbers.
> >
> >That's a great point Keith. And here's the nasty part: because they
> >waited until the issue was forced, they had to make it fully PI,
> >individual number by individual number. They lost the option to use
> >some sort of sensible grouping strategy.
> >
> I think we have carried this analogy to the point of silliness.
> Area codes still create groups.  But more importantly, the phone
> number can be an abstraction because it is only used 1 time during
> the call - at the beginning for the phone switches to setup the
> call.  Once that is complete and the query into the lookup table
> that matches the PI phone number to the internal routing number used
> by the phone company  is complete, the table isn't queried again.
> With IP traffic, to implement something similar to a PI IP address,
> you would have to have every non-edge router on the Internet make
> a query to a lookup table of some sort, and they would have to do it
> for every packet.  For a VoIP phone call that might have 10,000
> packets in the entire call that passes through the routers during
> call existence.  You can't do a query for each packet.  That is why
> IP is still going to require some sort of "sensible grouping"
> and why telephone numbers don't.

Not really.  The first non-edge router could look up a "physical"
IP address, cache it, and forward all packets for the "virtual" PI
address to that physical address (encapsulated with the original
virtual address still attached.)  The "physical" address could be
either the current provider-provided PA address of the destination
or the address of a router "close" to the destination.  If its a router
at that address it would then extract the original packet and forward
it to the (close-by) destination.  None of the intermediate routers would
have to know anything about the destination PI address.  The only
time you would need to do a second lookup of an established (i.e.
recently used) connection is if the cache overflowed, or the
destination physical address died, or if the destination router
decided there was a better route to the virtual destination address.

(N.B. This encapsulation could either ipv4 or ipv6 packets and the
virtual source/destinations could also be either ipv4 or 6.)

This is pretty much how cell phones work (where the "virtual"
10-digit phone number gets re-routed every time it changes cells),
and how number portability works for regular PSTN numbers, at
a huge degree of abstraction.

Telephone numbers don't require grouping precisely because a lookup
like this is done at call origination time (and for cell numbers,
on the relatively rare occasions when a phone moves to a different
cell.)  I'm not as familier with IP routing, but I get the impression
the routing folks are looking into exactly this sort of thing.  It
would be enormously useful for things like mobile VOIP.

> Ted
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John Santos
Evans Griffiths & Hart, Inc.
781-861-0670 ext 539

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