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From: brian@telebit.com (Brian Lloyd)
Newsgroups: comp.dcom.lans,comp.protocols.tcp-ip
Subject: Re: What protocol is used for leased lines?
Keywords: serial leased SLIP PPP
Message-ID: <1991Apr14.050154.16581@telebit.com>
Date: 14 Apr 91 05:01:54 GMT
References: <1991Apr12.140404.19947@homecare.uucp>
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The problem with what to run on leased lines is an old one.  Until PPP
there simply was no standard.  You ran what your router vendor gave
you or you ran SLIP over an async link.  Interoperability was limited
to SLIP and because SLIP runs only on async links, you were limited to
relatively slow speeds. 

Now you did not mention your hardware base so I can't comment too
much.  If you are trying to plug directly into an async serial port on
a workstation, your speeds and options are limited.  If you are
establishing connections between routers that is a different story.

You mention DSU's but you also mention RS-232.  Usually when someone
mentions a DSU he/she is running a 56Kbps or T1 synchronous link, the
former being only marginally compatible with RS-232 (the official
"top-speed" of RS-232 is 20Kbps but you can push it to 56bps) and the
latter is totally incompatible with RS-232.

All of that aside, I would consider adopting PPP as your
point-to-point link protocol.  It will run on either sync or async
lines.  PPP is supported by just about all of the router manufacturers
for their synchronous serial links.  It can also be used on
asynchronous links too so it is a win all around.  There are public
domain versions of async PPP floating around so you can put a network
together on a shoestring budget.  

Actually, you are going to be out of pocket quite a bit if you are
talking about leased lines so you might as well do it right and get
good routers to tie the whole thing together.  Run sync PPP.

-- 
Brian Lloyd, WB6RQN                              Telebit Corporation
Network Systems Architect                        1315 Chesapeake Terrace 
brian@napa.telebit.com                           Sunnyvale, CA 94089-1100
voice (408) 745-3103                             FAX (408) 734-3333