On 11/09/2012 15:59, Andrew Sullivan wrote: > On Tue, Sep 11, 2012 at 02:45:12PM +0100, Brian E Carpenter wrote: >> Thanks. Then it seems to me that a recommendation about the desirable >> behaviour >> of getnameinfo() and getaddrinfo() needs to be made, consistent with the >> final >> recommendation for mDNS vs DNS. At least we should describe a consistent >> deployment scenario. > > But you can't _make_ such a recommendation, because different > scenarios -- network-topologically indistinguishable from one another > -- require very different conclusions.
Surely we can recommend, or at least suggest, that the library which provides getnameinfo() tries both mDNS and DNS and returns the results in a configurable order. And if we can't do that, surely we can describe scenarios and their consequences. As Fred, I think, said the app is going to have to do something happy-eyeballs like but we can help it along the way. Brian > This is exactly the same problem MIF faced with the DNS server > selection logic. You naturally want to use the DNS server that you > believe is going to provide you with the right answers. But when you > move networks (say, into the coffeeshop which is using Stupid DNS > Tricks to authenticate you as a customer first), you actually need the > _least good_ answer sometimes, in order to move you from your > expensive mobile radio onto your cheap wifi. > > The same problem crops up here. Inside your house, mDNS is perhaps > the right answer. But for bookmarking on your laptop that you carry > on the road but want to use with your home network then, it's exactly > the wrong answer. So this once again comes down to use cases, and > trading userland functionality against complications that make the > specification complex, and implementations tricky and therefore buggy. > > To moan just a little bit, this is why many of us think that the > mutliple namespace approaches (seen in mDNS, llmnr, before those > NetBIOS, and so on) are harmful. Inevitably, these systems get hooked > up to the wider Internet, and the inconsistencies thereby revealed > make people confused. (This isn't to say there is an obvious better > answer, given the facts of the world about DNS name registration and > resolution.) > > Best, > > A > _______________________________________________ homenet mailing list [email protected] https://www.ietf.org/mailman/listinfo/homenet
