Thus spake "Keith Moore" <moore@cs.utk.edu> > > | To assign more than one address to every host means the host > > | must have an intelligent means of deciding which address to use. > > > > Yes, but the amount of intelligence actually needed is pretty minimal. > > (It is actually harder to decide between multiple available global > > prefixes, than to decide between global and site local - the former is > > a difficult problem, the latter is almost trivial). > > disagree. the app can choose any global prefix and reasonably expect > it to work, modulo link failures. Nit: the vast majority of apps today bind to INADDR_ANY (or its IPv6 equivalent), so it's really the OS which is choosing the source address. If the app binds a specific source address, it is invariably user-configurable and thus not an application problem. > but when choosing between a global and a site local the app needs to > know whether the site local address will be valid for the hosts that need > to use it, and it has no way to know this. Well, since one can easily determine whether the destination address is SL or not, picking a source address of the correct class is trivial. > the app may also have to choose which interface to use with the site- > local prefix, and it has no good way to know this either. Ah, but it'll have a different SL address on each interface, so that's no worse than having multiple global addresses. The truly interesting case is connecting to a LL address with multiple interfaces. S Stephen Sprunk "God does not play dice." --Albert Einstein CCIE #3723 "God is an inveterate gambler, and He throws the K5SSS dice at every possible opportunity." --Stephen Hawking