Path: utzoo!attcan!uunet!lll-winken!lll-tis!helios.ee.lbl.gov!pasteur!ucbvax!amdcad!rpw3
From: rpw3@amdcad.AMD.COM (Rob Warnock)
Newsgroups: comp.dcom.modems
Subject: Re: TrailBlazer and UUCP
Message-ID: <22820@amdcad.AMD.COM>
Date: 3 Sep 88 08:49:44 GMT
References: <467@njsmu.UUCP> <6453@chinet.UUCP> <4560@umix.cc.umich.edu> <6469@chinet.UUCP>
Reply-To: rpw3@amdcad.UUCP (Rob Warnock)
Organization: [Consultant] San Mateo, CA
Lines: 38

In article <6469@chinet.UUCP> les@chinet.UUCP (Leslie Mikesell) writes:
+---------------
| OK, I'm open to suggestions.  What is the best way to do file transfers over
| a satellite link?  I will be working with a ku band system...  at least a
| 2 second delay plus any internal packet contention. Physically, the connection
| looks like an X.25 pad...
+---------------

You might seriously consider TCP/IP! That's right, TCP/IP with SLIP on
the async line. I have benchmarked file transfers over a Telebit Trailblazer
from a VAX-11/780 (standard Berkeley 4.3 w/ SLIP driver) to a PC with Phil
Karn's "KA9Q" code and I found that by tuning the max-seg size and window
size I got disk-to-disk rates slightly better than I was getting with UUCP
over the same Trailblazer between two Unix systems. (The TCP/IP rate was
875 bytes/sec; UUCP was 820. The Telebit was configured to a "locked" 9600
baud, not 19200, as one of the UUCP sites had a rate limit. TCP MSS = 512,
window = 4096.) By cranking up the window size, you should get acceptable
results over your satellite link. After all, the ARPAnet uses TCP/IP over
satellites... ;-}  ;-}

+---------------
| Also keep in mind that I do not have uucp source so any changes will have to
| be a replacement for uucico rather than a modification...
+---------------

The KA9Q source is available for non-commercial use, and can run both
on a PC and in user mode on a Unix system that does not have any networking.
(Phil Karn will negotiate commercial rights.) There are also other sources
for TCP/IP software. But any Unix system that supports SLIP should be usable
(with some tuning, to be sure).


Rob Warnock
Systems Architecture Consultant

UUCP:	  {amdcad,fortune,sun}!redwood!rpw3
ATTmail:  !rpw3
DDD:	  (415)572-2607
USPS:	  627 26th Ave, San Mateo, CA  94403