Erik Nordmark writes: > I don't think stable addresses per se is the key > thing - it is the robustness of the communication > that is important.
I agree with this. However, the minimal degree of robustness is working at all - something which requires some address of some sort. There needs to be a way to get an address when you don't have a provider. This means either scoped addresses as we have defined them already (and in multi-link locations, this means either site-local or multi-link subnet routers and link-local), or some sort of provider-independent address (note there are various types of these as well, depending upon whether we believe they should be explicity non-routable, or privately routable between multiple non-connected 'sites'). > This robustness has at least two factors that are > relevant in this discussion: the stability of the > addresses, and the leakage of non-global scope > addresses. I think the question is how to > weigh those together. Regarding leakage of non-global scope addresses, I don't see this as a major problem given the way our current scoped addresses are defined. Having an explicit prefix makes it straight-forward for border routers to filter them. The scope-id in the sockaddr field makes it easy for applications to know on which interfaces an address is usable and to whom it is legit to pass (something that isn't true for the 169.254.x.x "link-local" addresses in v4 today). I'd be more worried about leakage of provider-independent addresses which don't share an explicitly non-routable prefix. > In any case, for a home user I suspect that the > value/importance of local communication would > typically be less than the value/importance of > global communication. As I mentioned in my last message on this topic, I believe a lot of the argument around site-locals is really about expected usage models. Personally, I would expect the opposite of what you say above. Home users watching a movie on their IPv6-enabled television screen in the living room (which is streaming in from the media server in their basement) won't be happy if their movie quits because their kid just dialed into the Internet and the resulting global address advertisment required all site-local communication to stop. More generally, I don't want IPv6 to be just for the Internet. If we've done it right, IPv6 will be used for all sorts of communication between lots of devices which typically don't have network connectivity today. I'm worried that this working group too often sees things in terms of only traditional computers as the hosts, and the routers all belonging to organizations which have administrators to run them. We shouldn't try to dumb down IPv6 so that it only works well in the environment IPv4 was conceived in. > Finally, an enemy to robustness is complexity. > Site-locals add complexity in many places; > applications, two-faced DNS configuration, etc. Yes, needless complexity is bad. But site-locals don't add any significant complexity to applications (which I think I've demonstated enough in too many emails already). Many existing IPv4-only sites run two-faced DNS today, so there clearly are people out there who think it is worth it for reasons that have nothing to do with IPv6. If we think that's not optimal, we should be thinking about figuring out why they run their IPv4 networks that way today and come up with a better solution for them using IPv6. > So let's not loose sight of the fact that the > goal is a robust network. Sure. And scoped addresses have the potential to make the network more robust (I'd say that link-locals have already proved their worth in this regard). --Brian -------------------------------------------------------------------- IETF IPng Working Group Mailing List IPng Home Page: http://playground.sun.com/ipng FTP archive: ftp://playground.sun.com/pub/ipng Direct all administrative requests to [EMAIL PROTECTED] --------------------------------------------------------------------
