FTP Software's

                           SLIP Network Interface

The Serial Line Internet Protocol (SLIP) allows PCs to run TCP/IP over a
standard RS-232 asynchronous line.

Introduction

As personal computers become more powerful, it becomes advantageous to
include them as full network nodes on a LAN rather than waste their computing
power by utilizing them only as dumb terminals for larger hosts on the
network.  As full network nodes, PCs can transfer files to and from other
machines on the network, send and receive mail, and form virtual terminal
connections to other hosts.  Although there are many proprietary protocols
available for performing this function, most network administrators prefer
TCP/IP, the most widely implemented, non-proprietary industry standard
protocol family in use today.  TCP/IP is offered by hundreds of vendors
worldwide for a wide variety of personal computers, minis, and mainframes,
and is the clear solution in a heterogenous network where different machines
running different operating systems all need to communicate.

For some PCs, becoming a network node is simply a matter of adding a network
interface card and connecting directly to the LAN.  Many vendors now offer
cards allowing PCs to connect into an existing Ethernet, token ring, or X.25
network.  However, these network interface cards can be prohibitively
expensive, or the PC may be physically far away from the network.  In these
cases, connecting PCs to a LAN may be financially impossible for some users.

The Serial Line Internet Protocol, or SLIP, provides an inexpensive solution.
Rather than requiring specialized hardware to connect to the network, SLIP
provides TCP/IP communication capabilities through the existing RS-232
asynchronous serial port present on almost all PCs.  For occassional TCP/IP
communication on dedicated lines where speed is not of primary importance,
SLIP provides all the functionality associated with direct LAN access at a
fraction of the cost.

What is SLIP?

SLIP is a simply a packet framing protocol which defines a method of sending
Internet datagrams over a dedicated serial line.  SLIP is useful for allowing
a mixture of hosts and gateways to communicate with one another, and
generally operates with line speeds between 1200 bps and 19.2 Kbps.

SLIP traces its origins to the 3Com UNET TCP/IP implementation from the early
1980's, and was first fully implemented on 4.2 Berkeley UNIX machines around
1985.  While there are standards for IP packet transmission over Ethernet and
token ring LANs, X.25 lines, and even satellite links, there is no official
industry standard for IP encapsulation over RS-232 lines.  However, because
of SLIP's widespread acceptance and ease of implementation, it has emerged as
the de facto standard.

Both public domain and fully supported versions of SLIP are available for a
wide variety of systems.  It is included with the standard 4.3BSD UNIX
release, and is also available for Sun Microsystems machines and cisco
Systems' terminal servers.  In addition, SLIP implementations are available
for an assortment of personal computers, including the IBM PC, the Apple
Macintosh, and the Commodore Amiga. Because of SLIP's widespread
implementation, it is convenient as well as inexpensive.


SLIP support for PC/TCP

FTP Software's PC/TCP is an extensive TCP/IP implementation for the IBM PC
and compatibles.  PC/TCP makes your PC a full network node with a myriad of
useful networking programs, such as file transfer capability, mail service,
remote login with terminal emulation, line printer sharing, backup
facilities, and the Berkeley `r' commands.  PC/TCP supports RFC-standard
subnetting, routing, and domain hostname resolution, and is actively
maintained and kept up to date with the latest TCP/IP standards.  (For full
details on PC/TCP's functionality and support for other network interfaces,
request a copy of the PC/TCP brochure from FTP.)

PC/TCP's SLIP implementation supports host-to-gateway configuration, allowing
your PC to communicate to the entire local area network via a point-to-point
connection to a gateway.  For more information on PC/TCP for SLIP, contact
FTP Software.


This document is loosely based on Cisco Systems' Applications Note TS-1.
Used with permission.


	Part Numbers and Prices

I-205	$490	PC/TCP Plus for SLIP
PC-205	$400	PC/TCP for SLIP (without InterDrive)
K-205	$200	PC/TCP Kernel for SLIP (without applications)
KI-205	$290	PC/TCP Kernel with InterDrive for SLIP

(Specify network interface card).

Specifications subject to change without notice.
All product names are the property of their respective owners.

FTP Software, Inc.				617 246 0900 - Phone
338 Main Street					617 246 0901 - Fax
Wakefield, MA  01880				info@ftp.com - Internet
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