In short, limiting the size of TLA to 13 bits looks like a reasonable cut, today.
I want to add that for the TLA and AAAA record discussion I see nothing wrong with having a stage 1 solution and then stage 2 and we create the backwards compatibility as implementors. I realize we need to provide the best solution for dynamic addressing and for ISPs. But right now real customers want IPv6 on "Intranets", or private enterprises. We will see several products this year and customers will be able to start deploying IPv6 from vendors. Many customers do not want to move to private addresses and a total v4 NAT solution who need addresses today. They want to move to IPv6 and have a plan to participate on the Internet even before the ISPs start supporting their needs for IPv6. I will also say that Europe and Asia appear to be moving much faster than the U.S. ISPs to be IPv6 ready. The point of this mail is that we implementors of IPv6 can absorb updates to the Address Architecture and AAAA records and we have changed the addr arch twice and once enough where we updated our code on the 6bone, and are using the new specs. The implementors will do the changes we develop and that should not be a fear of anyone IMO. The essential architecture of IPv6 is done and most of us have our code base prep'd to support the evolutionary IPv6 fine tuning by this working group. It is not difficult to move forward here with changes. One of the things that has always driven the IETF processes is the "market". There is now a market for IPv6 and they want it right now. We need to give it to them as vendors, and I hope we view that need in our deliberations. Also we have some new players at the UNH bake-off this week and one of them is Microsoft. This is really good. /jim