I hear it was one of the first Internet's ideas - to declare well-known addresses in addition to the well known ports. On Mon, 10 Jan 2000, D'Arcy J.M. Cain wrote:
Date: Mon, 10 Jan 2000 14:23:24 -0500 (EST) From: D'Arcy J.M. Cain <darcy@druid.net> Reply-To: nanog@merit.edu To: John R. Levine <johnl@iecc.com> Cc: jabley@patho.gen.nz, nanog@merit.edu Subject: Re: Selection of Appropriate Local SMTP Relay
Thus spake John R. Levine
That's much too complicated. What we need are some well-known IP addresses, analogous to well-known ports, that are not routable on the global Internet, but that are assigned to standard services within each network, e.g.:
10.255.255.1 - DNS server 10.255.255.2 - SMTP server 10.255.255.3 - SOCKS server 10.255.255.4 - Web proxy
(Probably it's not a good idea to use network 10 here, better to reclaim a /24 from the swamp or allocate a fresh one.)
Now you set up your mail client to use 10.255.255.2 for SMTP, and wherever you're connected, it'll be the local SMTP server.
Advantages
0. Works with all existing mail clients, no code changes needed, just a one-time configuration. Once this is widely accepted, MTAs would ship with it as the factory default.
Some people have suggested something similar with a well-known-service pseudo-TLD that each network's DNS servers would serve up with the appropriate values for that network, e.g.
smtp.wks socks.wks webproxy.wks
I like that less because, as previously noted, lots of people never change their DNS config when they switch ISPs or roam, so they'd get the info for the wrong network. Better to use IPs which you know will be routed by the routers for the network to which you are actually connected.
Why not both? Instead of a private TLD, make a real one (wks.merit.edu?) and assign the numbers there. That way it doesn't matter who your DNS server is.
-- D'Arcy J.M. Cain <darcy@{druid|vex}.net> | Democracy is three wolves http://www.druid.net/darcy/ | and a sheep voting on +1 416 425 1212 (DoD#0082) (eNTP) | what's for dinner.
Aleksei Roudnev, (+1 415) 585-3489 /San Francisco CA/