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1994-04-07
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207 lines
_SLIP_in_330_lines_or_less_
by Rick Nyman (enyman@vt.edu)
Permission is granted to freely distribute unaltered copies of this file
with all credits intact. Feel free to email me with questions but make
sure the word SLIP is part of your subject to help me handle the volume
of questions that I have been getting. Unfortunately, I do not have
technical knowledge of a setting up and running a SLIP _server_, except
for using a computer running NOS (MS-DOS software) as a gateway and
that is not exactly a professional setup. Any other questions are
welcome though.
Happy netting!
What is SLIP?
Serial Line Internet Protocol, it is one of many ways that computers
on the internet can exchange data. I like to call it `serial ethernet'
as it allows computers to exchange IP packets as opposed to
straight ASCII.
Why is SLIP better than a `regular connection'?
SLIP allows computers to exchange IP packets, the basic data unit of
the internet. When you call a mainframe with a modem for a standard
log-in, the remote computer sends straight ASCII characters to your
computer (or terminal) and receives straight ASCII from your computer.
What is so special about those IP packets?
IP packets are the basis of the entire internet. Every internet
protocol is based on these packets. With a SLIP connection, any
computer can have the internet functionality of a computer hooked into
ethernet. Software is the limit. In fact, some people hook UNIX
machines up to the internet using SLIP. A remote user that calls into
those computers gets the same connection as if calling a UNIX host
with a `real internet connection'.
So a SLIP connection will allow people to call my computer?
Well, sort of. An internet connection is like a telephone line. In
order to make use of it, you much have accessories (answering machine,
phone, modem). If you have the right software, there is no limit to
what you can do. With my SLIP connection, I can open an FTP window,
be downloading a file as I am reading news, open a Telnet window to a
host and run Mosaic. The only limits are my computer's capability to
have that many applications runnning (and my desktop space in windows)
and the bandwidth of my connection.
What do you mean, bandwidth?
Bandwidth is the amount of data that a connection can handle. A T1
line (College campuses usually have a couple of these connecting the
campus to their internet provider, ANS in Va Tech's case) can handle
1.44 million bits of data per second. A 57.6k leased line can handle
57,600 bits of data per second. Slip is limited by the speed of the
data line or modem. I run a v.32bis modem which gives me 14,400 bits
per second. A 2400 baud modem is limited to 2,400 bits per second and
is generally considered too slow to SLIP, although that depends on
your demands and patience. Most well connected hosts can FTP files at
30Kbytes per second, about 20 times faster than I can transfer data
with my SLIP connection. If you have more than one virtual connection
over a SLIP connection, they have to share the bandwidth. The TOTAL
speed of data will always be somewhat less than the ideal speed
(although high speed modems with their data compression sometimes push
the speed above the 14,400 `official' speed).
More than one virtual connection? What are you babbling about?
SLIP is just a serial implementation of the IP protocol. This means
that it has the same capability as the `real' networks in that it
can handle multiple connections on the same connection. IP packets
have a destination address in the header that allows them to go to a
specific port on a certain computer. Just as a `fully connected'
host can handle multiple incoming and outgoing connections, so can a
SLIP connected computer.
Why would you want to have a SLIP connected computer for personal use?
While SLIP may seem useful only for computers that take incoming
connections (such as UNIX machines), many people are switching desktop
PC's to SLIP. It allows them to have more customized software, often
with a graphical interface not found with most UNIX systems. It moves
the computing load off the mainframes, as all SLIP requires is a
terminal server to pass the IP packets along. You do not need to
worry with binary file transfer to a mainframe, as SLIP by definition
handles all types of data and data can be sent to or recieved from the
distant computer without ever having to go through the local
mainframe.
Where can I get SLIP?
If you are affiliated with a university, ask your computing center
about it. If they don't have it, then there is not too much you can
do there. You must have a local dial in or data connection to use
SLIP. To the best of my knowledge, SLIP packets cannot be sent over
telnet connections.
If you are willing to pay for access, SLIP from an internet provider
runs from $30 a month to over $150, depending on the provider and your
needs. My service is $33 a month with 4 free hours per day through
Clark.net as an example. While I am at school (Va Tech), the cost of
computing resources is covered in tuition.
What can you do with a computer running:
UNIX?
Many versions of UNIX come with SLIP support as part of the
operating system. With a continuous SLIP connection to a UNIX
machine, you could basically have a full internet computer,
capable of taking incoming ftp, telnet, finger, and other
connections. Your only limit would be the computer's
capabilities and the bandwidth of the connection.
Macintosh System?
I know of telnet, mail, WWW, and other clients available for the
Mac platform, but not being a MAC person, all I know of is their
existance.
MS-DOS?
There are a few software packages out there, most of them require
a packet driver. All a packet driver does is provide a common
interface to the SLIP connection that is compatible with network
connections.
NUPOP: Developed by Northwestern University, NUPOP is an
outstanding software package. It combines mail, gopher,
telnet, ftp, and other services into a single program with
menus and mouse support. It also supports autodialing for
SLIP users that have to call over a modem to get connected to
their service. The only fault I can find with it is that it
does not support multiple virtual connections.
NOS: NOT FOR THE FAINT OF HEART, NOS is a program developed
by the Amateur Packet Radio community. It has telnet and ftp
SERVERS as well as mail, finger, and other miscellaneous
services. It provides the rough functionality of a UNIX box,
and although its interface is a little rough, it is extremely
functional and I have seen a couple hosts running the package.
Other packages. There are a good number of other packages,
including commercial ones such as FTP software's product line,
NCSA telnet, and other packages like NUPOP. I used the
Trumpet newsreader for a short time before I switched to
Windows packages. If you have SLIP, look around and keep your
eyes open, stuff's out there.
MS-Windows?
A relatively new addition to the networking scene, winsock has
opened the way for networking software to be released for the MS-
Windows environment. Similar to a packet driver, winsock
provides an interface between a packet driver and the networking
packages. (The latest Trumpet winsock has internal SLIP support,
eliminating the packet driver requirement for SLIP users).
Winsock is short for Windows Sockets. Winsockets gives
unprecedented power and ease of use for Windows networkers.
Trumpet winsock: This is the one I would recommend. I
believe Alpha 18 has been recently released with its dialing
scripts, although I am still using Alpha 17 version because it
works better with the dialer that I already have. It comes
with basic clients for FTP, telnet, and more.
Windows Eudora: This package is a nice mail client. If you
have pop access to your emailbox on a mainframe, this program
has full aliases, mail forwarding and redirecting, multiple
mailboxes for storing mail, finger and PH (phonebook) clients,
and a really nice interface.
Windows Trumpet: This package is the windows version of
Trumpet newsreader, one of the better known newsreaders. It
also has built in email (sending and receiving).
WinVN: This is another newsreader, one with a different
philosophy than the standard ones. It is more newsroaming and
less read-your-news-like-email oriented. Try it and see what
you think.
WS-FTP: This program is a very nice graphical FTP program.
(I call it point and click FTP for idiots, not meaning that in
a derogatory sense either) It remembers the FTP sites that
you call, allowing you to pick the site from a list (which it
automatically builds) and change directories/get&send files
all with simple mouse clicks.
WinQVTNet: This program combines a good telnet with excellent
vt100 emulation, nice FTP, and passable news, mail, and lpr
(printer)clients in one package. Although it is shareware,
the registration cost is quite reasonable for someone who
would use the services.
Mosaic: The absolute latest in internet toys, Mosaic and the
World Wide Web (I think WWW was developed by CERN in
Switzerland, Mosaic is by NCSA, someone correct me if I am
wrong) is like a cross between gopher and a Windows help file.
Hypertext links pointing to other hypertext documents on other
continents, gopher servers, telnet or ftp sites, and more.
Support for graphics makes it even nicer. Warning: This will
run a tad slow at 14,400 slip. I can't comprehend using it at
2400, it would be excruciatingly slow.
Hgopher: A nicely written gopher client, Hgopher has gopher
and gopher+ support as well as bookmarks.
EWAIS: I'm still playing with this package, but it is a Wide
Area Information Server client. You ask it a question and it
goes searching through servers to find that information.
Pretty interesting.
Hope this answers all the questions, if there are any other questions, I am
following most threads in alt.internet.services, if you don't get a
response from me in a day or two, send me email.
I am also hoping to post a file that someone on our campus put together
with better reviews of fewer winsock packages and the locations of the
files. I should get that one up in a day or two, as soon as I get
permission.
(Update on that file: The original author of that file is working on an
updated version and has asked that I not distribute the current version.
If you send me email, I will notify you when it is released. Make sure
that part of the subject of your message has the word SLIP in it, as I
have gotten many messages already and that makes it easier to handle the
volume.)
Rick...
enyman@vt.edu
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