Subject: 6coexist and draft-wing-app-6coexist-00

From: "Eric Vyncke (evyncke)" <[email-masked]>
Date: Wed, 17 Sep 2008 15:18:42 +0200

Dan and Iljitsch,
 
I've read with interest your I-D, some quick comments:
 
- frankly, stating that 'IPv6 connectivity is poor' (in the intro) would benefit from current data points (I'm afraid that IETF is shooting in its foot if we continue to write such statements :))
- starting several connections to the same web server over several networks (v4, v6, tunnels, translation) will probably not ease the task of all 6to4 relays, Teredo servers in the transition period
- not sure whether content provider will be happy to be bombarded by several connections from the same client (specially as the server has little clue to see that the requests come from same physical client)
- you may want to do more than simply opening a TCP connection (small packets), you may want to send more than 1,500 bytes in order to check whether Path MTU discovery works
- at least teredo requires a couple of RTT to get the first IPv6 packets going through it, so, you may want to move Teredo to the top of your connectivity check
- in its essence, it is looks like an asymmetric ICE
 
Regarding the question of whether to have www.example.com and ipv6.example.com and _WHICH_ party (server vs. client) decides, I've recently played with some JavaScript to verify
whether IPv6 connectivity is there and if IPv6 connectivity is reliable, the JS redirects immediately the browser to ipv6.example.com. This is actually the reverse of your I-D as it is the server which decides.
 
See also draft-vyncke-http-server-64aware-00 <https://datatracker.ietf.org/drafts/draft-vyncke-http-server-64aware/>  which describes further the technique. No rocket science as you'll see ;-)
 
Hope this helps
 
-éric
 
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