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Re: proxy shim with hash in upper address bits?

On 13-jul-2007, at 11:03, marcelo bagnulo braun wrote:
Another, possibly even harder to solve, problem with proxy shim is what happens when a host behind the proxy want to talk to a non- shim host. 


it depends what type of idetifiers are you using


Of course, I was assuming non-routable identifiers.
But quite possibly, we can solve this if we can make proxy shim interoperable with a LISP-like approach. So the user of the portable space would implement a shim proxy cq ETR/ITR which would obviously be able to talk to other shim proxy/ETR/ITR devices as well as to any host that supports shim6. Hosts that don't implement shim6 would have to reach hosts behind a proxy through ETRs that are deployed by their ISPs or possibly by the sellers of the portable address space.
how does this solve the backward compatibility problem? I mean you still need to deploy ETR/ITR in the remote site, so if you do that, you may well deploy any other box i.e a pproxy shim
Bottom line: proxy shim, shim6, lisp, you-name-it, they all require support from both ends involved in the communication (either host or a box next to the host (proxy, TR)) (and the multihoming benefits only apply to the path between the two multihoming aware boxes)
Yes, this is an important limitation. With shim6 in hosts, you can determine if the other side supports shim6 before selecting an unroutable identifier, and fall back on legacy IPv6 if it doesn't, but then you're not multihomed for that session. With LISP et al this isn't possible, but the logic doesn't have to be in the hosts, so as long as there is a box somewhere in the path that supports the protocol, you're in business. The degenerative case would be where the encapsuating devices for site X which is reachable through ISPs A and B are located in the networks of A and B.
Making (proxy) shim6 and LISP interoperable helps shim6 because the deployment of LISP boxes means more people to talk shim6 with, and it helps LISP because you get to optimize paths to a much higher degree because this can happen at individual hosts, even ones that are not served by a *TR device.