Newsgroups: ba.internet
From: rchilder@us.oracle.com (Richard Childers)
Subject: Re: SLIP
Organization: Memes-R-Us
Distribution: ba
Date: Fri, 14 Aug 1992 17:46:15 GMT
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              at Oracle Corporation.  The opinions expressed are those
              of the user and not necessarily those of Oracle.

bill@physics.Berkeley.EDU (Bill Craig) writes:

>I need to gain access to the Internet (ftp,telnet) for a small cluster
>of sparcstations that will be travelling to several sites over the next
>few months.  Since most of these sites are in the New Mexico desert it
>seems to me that the best way to do this is to buy a couple of high 
>speed modems/(bridges??) and use SLIP to link the remote cluster to
>an existing cluster now on the ethernet in Berkeley.  Since i know
>little to nothing about how all of this works, i'm hoping that someone
>on this newsgroup can give some advice about the best way to do this.
				.
				.
				.
>1) If i simply buy a pair of very fast modems,  what kind
>   of special phone lines do i need?  Seems like i remember that
>   sparc tty ports maxed out at 19.2 kb, is this speed fast enough to
>   make SLIP worthwhile?  What kind of modem would be best suited for
>   this?

No special phone lines, but your protocol converter vendor ([2], below )
will have recommendations.

>2) Presumably there are boxes with a phone line on one end and a 
>   thick/thin/10BaseT connector on the other that are designed for
>   this sort of thing.  This seems to be the real answer to the
>   problem.  Anything in my price range?  Any specific
>   suggestions for the best units,? phone line requirements?  

I'd call this a protocol converter, and I'd refer you to Cisco, which I
think is in Sunnyvale or Santa Clara. Also, if you call up ANIXTER, a
telecommunications company in San Francisco, they can provide you with
a thick catalog of products, basically everything you need to construct
a telecommunications infrastructure, up to and including routers and such.
ANIXTER would be able to clue you in on other vendors ...

>3) If i go with the modem option i'll need some SLIP software running
>   on both ends.  There is some mention of existing software in the
>   PCNFS documentation but not enough to tell me whether sparcs running
>   4.1.2 are SLIP equipped.  If not, where can i buy/ftp the software
>   i need.

PC/NFS has a serial-port option, it's true, but it's not true SLIP, as far
as I know, just PC/NFS, and as far as I know, 4.1.2 does not come with SLIP
built in. A friend who installed SLIP on a Sun 2/120 running SunOS 3.5 had
to add SLIP to the kernel by hand using public domain patches, and I'd
guess this is still what needs to be done. There are public domain versions
of SLIP available, although I haven't checked them out ... yet.

It's possible that I'm wrong about the above, but it seems to me that all
the SLIP setups I know of, commercially, are set up as subnets, which a box
acts as the gateway for in the routing tables. The gateway - a Cisco or
equivalent box - receives packets, and routes them to appropriate ports,
over the phone, to your modem, and in through the serial port, which the
kernel has been modified to recognize as a networking resource and read
and write accordingly. Once the packet is in the kernel, everything else is
pretty vanilla.

>4) And finally, if i use modems, my host machine in berkeley would be talking out a 
>   serial port to the remote cluster and would presumably pass packets
>   back out its standard le0 ethernet interface.  Do i need special
>   routing software to make it understand how to do this?

This setup is more common in a private SLIP setup, and I'd guess you'd need
to modify *both* kernels in this case, which may not be appropriate in all
cases. Perhaps some 2 meter enthusiasts might care to share their exper-
-tise here with SLIP, PCs, and BBSing ?

I think there's a tradeoff there in terms of simplicity vs. cost, buying an
explicit SLIP router versus making do with a couple of modems and kernel
modifications. I'd guess the SLIP router would allow connections to any
machine on the subnet, relying on routing, whereas the modem-specific port
would rely on the modem being free and operational, the kernel being free
of unexpected modifications by unknowing administrators, and the system
being up and running. As well as routing being in place.

>Apologies for the long and slightly inappropriate posting but i'm short
>of time and knowledge and it seems that the people who read this group
>are most likely to have the info i need...

I'm interested, too. All of the above is pure theory. And speculation, and
hearsay, and technical literature ...

-- richard

-- 
-- richard childers		rchilder@us.oracle.com		1 415 506 2411
         oracle data center  --  unix systems & network administration

                   Klein flask for rent. Inquire within.
Newsgroups: ba.internet