Keith, I did not argue the persistence of ALL DNS names. What I did argue is that if I was trying to tell someone how to reach a particular Internet based service I would write down something that had a DNS name in it, not something that contained an IP address. For me, that is a measure of persistence. I will not argue against the fact that IP addresses have the nice property that when a host A tells another host B its address (as the src address of an IP packet) that host A is reachable by that address. I would argue that property is not persistence, it is temporally bounded reachability (TBR - we can have a bof to get a better name). Now, let's look at most of the systems that you refer to that do not have a DNS name. How many of those hosts connect to the Internet using dialup connectivity and for the better part of the day do not even have an IP address? And what about those hosts that have DNS names inside their corporate networks, but their corporations elect not to publish those persistent names into the DNS for security fears? Is this what we are supposed to use as evidence that IP addresses are more persistent than DNS names? And when those hosts connect to the Internet, what do they use FIRST when they want to communicate with a peer? (now I have opened the dam here, haven't I? Strictly speaking they will use the IP address of "." to get going! Mcast DNS can fix that bug.). I am not suggesting that all hosts solely use DNS names as a rule. I will suggest if you want to advertise services and hosts then use DNS names because that is what works. And I am also arguing that you can get "good enough" roaming if you use DNS names. And I am asking whether anyone can actually prove that DDNS is not scalable (preferably for real Internet applications and uses). Regards, peter (P.S. And shouldn't you be asking: "Peter, if you really want hosts to register their tunnel ends in the DNS, isn't the most likely implementation one where the host gets a persistent IP address, and gets many TBR IP addresses over time?" - cheers, peter) -----Original Message----- From: Keith Moore [mailto:moore@cs.utk.edu] Sent: Friday, March 01, 2002 8:25 PM To: Peter Ford Cc: Geoff Huston; ietf@ietf.org Subject: Re: utility of dynamic DNS > I would offer that we select the "thing" that looks the most persistent > to be the persistent identity. Actually, you want to select the identity that's appropriate for your purpose. DNS is not inherently better than IP for all purposes. DNS names are often failure-prone, slow to lookup, and/or out of sync with reality. > If the choices are: DNS name vs IP address, I think most people would > recognize that the DNS name is the persistent identity. And if 'most people' treated this as a general rule, they'd be wrong. There are several situations where IP addresses are more usable than DNS - the DNS name may not even exist, lookups may not work outside of a realm, or the name may be bound to an IP address rather than a host. It is highly dependent on the configuration of the network where the hosts are located and the DNS servers that serve them. See draft-moore-nat-tolerance-recommendations-00 for a more detailed explanation. > We should probably try to move the debate from "proof by emphatic > assertion" to analysis. Presumably that also applies to assertions about persistence of DNS names. Keith