Path: utzoo!utgpu!utstat!jarvis.csri.toronto.edu!mailrus!wuarchive!gem.mps.ohio-state.edu!swrinde!cs.utexas.edu!uunet!mcsun!ukc!edcastle!dcl-cs!aber-cs!rupert!pcg From: pcg@rupert.cs.aber.ac.uk (Piercarlo Grandi) Newsgroups: comp.protocols.tcp-ip Subject: Re: MX-registration vs %-hack (was Re: New Host-Requirement RFCs) Message-ID: Date: 27 Oct 89 13:45:51 GMT References: <8910201839.AA29376@arcturus.mitre.org> <1989Oct23.173855.1370@utzoo.uucp> <7696@ditmela.oz> <31038@news.Think.COM> Sender: pcg@aber-cs.UUCP Organization: Coleg Prifysgol Cymru Lines: 74 In-reply-to: barmar@kulla's message of 25 Oct 89 07:20:59 GMT In article <31038@news.Think.COM> barmar@kulla (Barry Margolin) writes: 1) Users have to remember gateways. smart@ditmela.oz.au is easier to remember than smart%ditmela.oz.au@uunet.uu.net. 2) % isn't the only such hack, and it's not always clear what happens when multiple hacks are used together. What is the meaning of foo!bar%baz@quux? Is it quux -> foo -> baz -> user bar or quux -> baz -> foo -> user bar? True, true, and this is why domain names are *a good thing*. 3) Problems occur when network topology changes. If uunet.uu.net is replaced as the Internet->UUCP gateway, all the %host@uunet.uu.net addresses are invalidated. Ahhhhh. This is the crux: %host@uunet.uu.net is a *route*, not an address. In the absence of centralized administrative control, users will *always* be required to eventually use routes; the address->route translation cannot be *always* performed by some kind of distributed database, without centralized administrative control of *both* the naming and transport. I am one of those that think that centralized administrative control is not only impossible, it is also not very desirable. People that do not see beyond the Internet think otherwise on both accounts. This means that users must learn a new gateway, and mailing lists all over the place have to be updated. The domain system simply requires updating the database, and users never notice. Ahhhhh. Another difference of point of view. You are assuming there is a benevolent entity that automagically updates in real time (or close enough) the naming and routing distributed databases. This does not happen in the real world, *even* on the Internet (where it is close enough though). Lazy or untrained system administrators, mistakes, etc... 5) You're dependent on an arcane, nonstandard feature being implemented on a host over which you have no control. Uunet may decide at any time to stop supporting %, and you'll run into problems. Besides encouraging hosts to switch away from %, I think they are also encouraging new systems NOT to implement it in the first place. Yes, but what is the alternative for source routing? The multiple "@" hack is not an answer... Note that you cannot say "don't do it", unless you have centralized control over naming and transport. Again and again I am skeptical of the feasibility of doing this; it is already difficult (and I occasionally think it is impossible) to switch away from relative naming, because it is difficult enough to have centralized control over the namespace; to have centralized control over transport is probably impossible or even undesirable. Again and again I think (nostalgic) that if everybody had adopted the Usenet/uucp bang notation for BOTH naming and routing everybody would be happier now (well, I would have liked to have more then 7 chars for host names, to make it easier to have unique names, or to support dot notation for domains). More importantly, it sends a signal to implementors not to try related kludges. For instance, I've heard of systems that try to parse non-local local parts, in an attempt to optimize routes. They see foo%bar@baz, realize that they know a host named "bar", so send the message directly to bar rather than routing through baz; this loses if baz doesn't interpret % as they think it does, or if baz has a different notion of the host bar. Amen! May the heathen be stricken by data rot! -- Piercarlo "Peter" Grandi | ARPA: pcg%cs.aber.ac.uk@nsfnet-relay.ac.uk Dept of CS, UCW Aberystwyth | UUCP: ...!mcvax!ukc!aber-cs!pcg Penglais, Aberystwyth SY23 3BZ, UK | INET: pcg@cs.aber.ac.uk