OMB: IPv6 by June 2008

Fri Jul 8 23:40:40 UTC 2005

Small detail:

On 6 Jul, 2005, at 16:30, David Conrad wrote:

> If IPv6 had actually addressed one or more of routing scalability,  
> multi-homing, or transparent renumbering

These are the same problem, looked at in different ways.

The issue is: graph-sorting scalability demands abstraction;  
abstraction demands abstraction boundaries; abstraction boundaries  
must be reflected in node names (i.e., locators); nodes are  
physically portable, topologically portable, or both.

To be fair, mass deployment of local wireless LANs for large numbers  
of people with portable equipment they carry with them from meeting  
to hotel room to coffee shop to airport lounge to home would not have  
been the obvious future for anyone in the ROAD process.

However, this is today's reality, and the movement of "named things"  
is more likely to increase than not.

"Stretchy LISes" has mostly hidden the physical portable aspect of  
named things.     Bridging is ancient and well-understood.

Logical portability happens too, for individual named things and  
varying-sized collections of them.

The stretchy LIS approach works at a cost of header overhead and  
inefficient traffic flow.   The widespread use of VPNs demonstrates  
this well.

The alternative is to deal with disjunctions between the named thing  
and its topological location.

Model A: you go from office to IETF meeting, the IP address you use  
to talk to the world stays the same, and comes from your office's  
address space.   You use VPN technology to make this happen.

Model B: you go from office to IETF meeting, and the IP address you  
use to talk to the world comes from the IETF meeting's address space.

Now go to your hotel room.   Model A: your socket-like things are  
still bound to the office address, and if you walked briskly enough,  
your sessions are likely still alive when you reconnect to your  
office with the VPN tech.

Model B: oops, you have a new address.   You can't use the old  
address.   Your sessions are very likely toast.   Good thing there  
are tools like screen(1) and restartable ftp!

The difference between A and B is independent of the header formats,  
so long as the named thing normally overloads its identity and location.

Model A allows for a disjunction between the identity and location,  
by bridging through the real topology to connect to a distant  
collection of addresses, abstracted via variable-length prefixes.

Model B does not allow for a disjunction in the absence of a session  
protocol, in which case the session layer identifier is the named  
thing, and the current IP address is the locator.

The session layer does not have to be particularly heavyweight, it  
does not have to be distinctly "above" the network and transport  
layers, it does not have to be the only session support available to  
the other protocols in use between communicating entities.

Integrating renumbering-adaptability within the lower (N/T) has some  
attractions especially with regard to preserving the traditional  
datagram and octet-stream modes, reducing the peer-to-peer  
handshaking in the event of renumbering of one of the parties, and in  
leveraging the current DNS architecture.

It would also eliminate the market need for NAT as a tool to assist  
in -- or avoid -- large-scale simultaneous renumbering as when a  
single-homed site switches ISPs.

> Instead, IPv6 dealt with a problem that, for the most part, does  
> not immediately affect the US market but which (arguably) does  
> affect the other regions.  I guess you can, if you like, blame it  
> on the accountants...

People should blame it on the multiplexors.

There is lots of scope for multiplexing address use: not everyone is  
awake and powered on simultaneously; not everyone really does need to  
accept inbound connections from *everywhere*, at least not all the  
time; not everyone needs to run a particular service on the same  
numbered port; some services are fine with uniqueness involving  
network-layer-addresss+protocol+port(+possible other things).

NAT, like other forms of multiplexing the Internet has benefited from  
(e.g. TDM, WDM, time-sharing operating systems, ...), can allow for  
more efficient in one's use of limited resources -- in this case,  
aggregated address space -- in a way accountants seem able to cope  
with.   Yes, TANSTAAFL.

     Sean.