Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!pasteur!ucbvax!NNSC.NSF.NET!craig
From: craig@NNSC.NSF.NET (Craig Partridge)
Newsgroups: comp.protocols.tcp-ip
Subject: re: Dial-up SLIP?
Message-ID: <8901242208.AA01980@ucbvax.Berkeley.EDU>
Date: 24 Jan 89 17:40:35 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 51


> I heard about dial-up SLIP, but no details.  All I know is that Telebit
> people are looking forward to it (my words), and that there was a version
> developed by BBN and/or CSNET.

> Is there any more information available?  Is the code available?

Jacob:

    There are several implementations around, in vary forms of stability.
To my knowledge only the CSNET one is currently being distributed, and
only to CSNET members (the code was developed using CSNET revenue).  Other
sites with dial-up IP software include the University of Tokyo and BRL.

The CSNET software is described in a paper being given next week
at the Winter USENIX conference.  [L. Lanzillo and C. Partridge,
"Implementation of Dial-up IP for UNIX Systems," Proc. 1989 Winter
USENIX, San Diego, Calif.]. The key features are:

    - It drops into binary BSD distributions (e.g. SUN)

    - It makes connections on demand. When a packet hits your dial-up
	gateway for a remote site that isn't currently connected,
	the gateway will dial the phone and establish the link
	(while the datagram waits).  Note that the delay in dialing
	the phone is long enough that you probably don't want to
	do more than one such dial-up hop (i.e. dial-up IP works
	best with star topologies).  When the dial-up link has
	been idle for a few minutes, the line hangs-up.

    - There are some basic access controls so that the phone link
	can only be established at times that you agree to incur
	charges, and only by hosts that you chose to allow to
	establish the connection.  These facilities are optional,
	and once the link is up, anyone can use it.  (We'd like
	to put in traffic filtering but are still dithering about
	the best way to do it).

I believe the U. Tokyo software is similar [ J. Murai and A. Kato,
"Current Status of JUNET," Future Generation Computer Systems, Vol. 4,
No. 3, October 1988].  The BRL software (last I heard) requires more
active user intervention -- i.e. you dial the phone and then start
SLIP over it. Phil Karn also supports some form of dial-up SLIP with
his KA9Q package (he's used it to connect to the CSNET dial-up IP
gateway).

Craig

PS: My impression, based on very little testing, is that all these
implementations are culturally compatible and that with a tiny bit
of work, we could probably make them all interoperate.