--On Sunday, 28 December, 2008 16:22 -0500 John Day <jeanj...@comcast.net> wrote:
> Why should an application ever see an IP address? > > Applications manipulating IP addresses is like a Java program > manipulating absolute memory pointers. A recipe for problems, > but then you already know that. John, Let me try to explain, in a slightly different way, what I believe some others have tried to say. Suppose we all agree with the above as a principle and even accept your analogy (agreement isn't nearly that general, but skip that for the moment). Now consider an IPv6 host or a multihomed IPv4 host (as distinct from multihomed IPv4 network). The host will typically have multiple interfaces, multiple IP addresses, and, at least as we do things today and without other changes in the architecture, only one name. One could change the latter, but having the typical application know about multiple interfaces is, in most cases, fully as bad as knowing about the addresses -- one DNS name per interface is more or less the same as one DNS name per address. Now the application has to pick which interface to use in, e.g., opening a connection to another system. Doing that optimally, or even effectively, requires that it know routing information. But requiring the application to obtain and process routing information is worse than whatever you think about its using IP addresses -- the latter may be just a convenient handle ("blob") to identify what we have historically called an interface, but having the application process and interpret routing information is completely novel as far as the applications layer is concerned (as well as being a layer violation, etc., etc.) and requires skills and knowledge that application writers rarely have and still more rarely should need to use. At least to me, that is the key architectural problem here, not whatever nasty analogies one can draw about IP addresses. john _______________________________________________ Ietf mailing list Ietf@ietf.org https://www.ietf.org/mailman/listinfo/ietf