On Tue, Feb 2, 2010 at 2:41 AM, Robin Whittle <r...@firstpr.com.au> wrote: > > I can't think why an IPv4 application which has been made to work > from behind NAT, I guess with specific messy protocols and external > servers to trick the NAT box into allowing various things to happen, > would be easier to modify for IPv6 operation. As far as I know, > making an application able to operate from behind NAT isn't some > special generalised independence from how each host is connected or > where, which would somehow ease rewriting the code for IPv6. > > This is pretty generalised discussion. Can you think of some > examples?
One example is HTTP and the usage of cookies. If you have a lot of clients (thousands) behind a forwarding proxy then how to do server load-balancing in front your servers? You can't use the source address to identify a unique client, every client behind the proxy is having the same source address in their connections to the server. So the ADC in front of your server usually identifies the clients by the help of cookies, and direct the client always to the correct "real server". So when the connection lands at the real server the source address has been changed by the forwarding proxy and the destination address has been changed by the ADC (if the ADC operates in L3 mode) - NAT everywhere and far from easy to troubleshoot http://en.wikipedia.org/wiki/HTTP_cookie And you can try it yourself, take a session to a web site, shut down your interface and use another interface to continue on the same site. Most likely the site will continue to serve you from where you left off. A cookie is an identifier that is decoupled from the address space and network layer, the more these kind of applications there is deployed the easier it would be to change the network and address architecture. I think that the SCTP verification tag and MP-TCP token has similar characteristics, and they are more of general nature and not so much tied to a certain application. Both the verification tag and token are 32-bit, if these transport protocols becomes more used the middleboxes could start to track sessions with the help of the 32-bit "session identifier". MP-TCP is for TCP only, UDP should be abandoned and SCTP shuold be used instead - but SCTP is plagued by the evil NAT and thus there is a catch-22 situation. This is an architectural discussion/speculation and there is a lot of hurdles to get us there, maybe impossible to achieve... -- patte _______________________________________________ rrg mailing list rrg@irtf.org http://www.irtf.org/mailman/listinfo/rrg
