Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!decvax!bellcore!ulysses!mhuxr!mhuxn!ihnp4!ucbvax!SCRC-YUKON.ARPA!Margulies From: Margulies@SCRC-YUKON.ARPA (Benson I. Margulies) Newsgroups: mod.protocols.tcp-ip Subject: re: Port Collisions Message-ID: <860514144516.8.MARGULIES@REDWING.SCRC.Symbolics.COM> Date: Wed, 14-May-86 14:45:00 EDT Article-I.D.: REDWING.860514144516.8.MARGULIES Posted: Wed May 14 14:45:00 1986 Date-Received: Thu, 15-May-86 23:48:38 EDT References: Sender: daemon@ucbvax.BERKELEY.EDU Organization: The ARPA Internet Lines: 39 Approved: tcp-ip@sri-nic.arpa Date: Tue, 13 May 86 21:22:49 -0400 From: Craig Partridge > We here at Symbolics are concerned with the process of assigning TCP/UDP > port numbers. It is not always appropriate for us (and other vendors) > to apply for ports in the Czar-controlled first 256 ports. Either > because of time constraints or issues of proprietary information, we > cannot always write and distribute an RFC for each of our protocols. Why not make the port numbers used user/site configurable? Berkeley actually did this quite nicely with a services list, which mapped a service name/protocol pair with a port number. Since programs use this database (or are supposed to) to find out what port they are supposed to us, one could run SMTP on TCP port 25 on the Internet but port 243 on some private network if one so chose. We believe in 'plug-in-and-play' software. Expecting not-very-savy users to figure out the port usage of all the various programs they are using is a big expectation. What if two sites disagree on the port for a protocol? They will never be able to inter-operate! We have logical services and protocols that are mapped to ports. The only way to make that do what you want is to use a different protocol name for each port assignment in use anyplace, so that the database of hosts can indicate which hosts are going to talk over which ports. This is an unreasonable burden. The advantage is the vendor need not necessarily worry about what port you pick for your special application -- it can always be changed among cooperating machines. Its the vendor's job to worry so the user dosen't have to. Craig Partridge CSNET Technical Staff