On 8 dec 2007, at 20:34, Brian E Carpenter wrote:
Would it be possible to evaluate deployment issues, i.e., whether said mechanism is already available today in hosts, and if it isn't, whether it can easily be implemented in a modular way so it can be added by others than the OS vendor?
I think you also have to consider whether there's something to tunnel *to* - is there a significantly large class of dual stack services that will be able to make use of tunnels? And don't forget the third class of solution: application level proxies. Would you advise the operator of a large IPv4-only web site to a) dual-stack the whole site b) install a dual-stack proxy for IPv6 clients c) install a layer 3 translator for IPv6 clients?
As I said in the second session, dual stack isn't an appropriate mechanism for client computers. If we had that kind of address space we wouldn't have to have this discussion.
Proxies are good but generally don't address UDP applications and are ususally a binary thing: either you proxy pretty much everything or you don't proxy at all. However, a mechanism where only sessions towards destinations using the unsupported IP version are proxied would be very useful, and if everyone who isn't dual stack used one, referrals wouldn't have to be a problem, either.
A layer 3 translator is basically a more generic implementation of a proxy. It has the advantage that it can support more protocols than most proxies and possibly v4-v6-v4 operation, which would be nice in a situation where you have IPv4-only legacy devices but an IPv6-only network.