> How do site-locals work? > > For a single-sited host, I think the main requirement is > draft-ietf-ipv6-default-addr-select-09. For applications that send > addresses to correspondents (note this is a small minority of > applications) it can get more complicated but it's still not bad - see > kre's recent emails about this. I know MS is porting/developing such > applications but I'm not involved.
I'd agree as long as the single-sited host is not connected to the global internet. When connected to the global internet, many applications will work just fine. But there are some application protocols as currently defined which do not work. It would seem useful to try to identify the classes of applications which break in these configurations and what actions need to take to occur to update the protocols and/or applications to allow this to work. Once this is understood, it would be easier to gauge whether using site-local addresses when a site is connected to the global internet is worth the effort. > For DNS, I implemented draft-ietf-ipngwg-site-prefixes-05 and it works > great. Unfortunately since that draft seems to be dead, I think the > fall-back for now is that to use site-locals you'll need a two-faced > DNS. Yes, although not pretty two-faced DNS works for single-sited hosts. > For a multi-sited host, one additional requirement is that applications > should deal with sockaddrs instead of directly with addresses, so that > the scope-id is preserved & passed around as needed. Another additional > requirement is routing table lookup needs to be cognizant of scoping. If the DNS resolver fills in the appropriate scope zone ID for site-local addresses, then the application can use the sockaddr for communication. How the scope zone ID gets filled in, and how the DNS resolver queries two-faced DNS name servers in different sites and consolidates the (now different) responses is what has not been defined. For instance, since each site would need to run two-faced DNS to allow site-locals to be placed in DNS, each may return different results for the same host. Depending on which site the DNS query is sent and how DNS is configured, the resolver may receive no addresses, only global addresses, or a mixture of global and site-local addresses. This was covered on this list previously with no agreed-upon resolution on how to make this work, not to mention any IDs with concrete proposals to be reviewed. There are, of course, additional issues for multi-sited hosts. At a minimum, there are the routing changes which have been discussed here previously, and possibly others which have yet to be identified. None of this is insurmountable. With sufficient architecture and updates to susceptible applications, support for multi-sited hosts can likely be made functional. Whether it is worth the effort is a different question, though, and one which only this WG can answer. Roy -------------------------------------------------------------------- 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] --------------------------------------------------------------------
