Date   : Sat, 04 Aug 2001 16:52:24 +0100
From   : "Chris Thornley" <C.J.Thornley@...>
Subject: BBC TCP IP Stack (OverView)

Hi,
I just want to provide an overview of what a TCP/IP stack is as there seems
to be some confusion. These deal with (Addresses).

SLIP   Is an implementation of IP protocol over the serial medium
PPP    Is an implementation of IP protocol over the serial medium
PLIP   Is an implementation of IP protocol over the parallel medium

SLIP was the first it contained no Dialler and allowed the user to connect
with a dialler to another user running IP. Settings had to be set manually
and tended to be static. Also authentication had to be manually entered each
time.

PPP was much improved over it predecessor this still did not provide a
dialler but allowed automatic configuration and authentication.

PLIP Is a parallel implantation of IP. This been developed for Linux,Amiga
and DOS based PC and allows TCP to be used over the parallel port. No
automatic configuration or dialler.

Some companies combined TCP suite with SLIP PPP etc and called them a stack
but technically that's not accurate.

TCP Low Level Protocol Suite

This consist of TCP UDP and ICMP (Deal with Ports)

ICMP a basic protocol used mainly for diagnostic purposes i.e. PING echo and
machine detection. Is being phased out due to potential security problems
and is usually blocked by firewalls giving the impression the machine not
there.

UDP (User Datagram protocol) Similar to TCP except not a robust. Contain no
method of sorting or sequencing packets and used when you don't want a
permanent connection to a device. This can be use to receive a clock signal
as you don't care if a packet late and Is use extensively in file and
directory sharing.

TCP (Transport Control protocol) Used more extensively on the internet and
is more complicated. similar to UDP but provides packet sequencing and
acknowledgement.

All 3 of these protocols are directed to ports. Address of computers are
placed in the IP protocol

I have some protocol programming links and information if anyone interested
and a link to an article in an electronics magazine which implements a PC
ISA network card either by 8 bit IO port or Serial and might be good for a
project of this nature. This has a rudimentary TCP implementation in its PIC
Chip

Some programming libraries might be best implemented for this.

The best way to implement an interface is to treat everything as if it
writing to a file. Using Ip Address, Port, Data sort of analogous to
Filename Channel Data used by BBC files.

Other tools i.e. FTP Telnet mail are implemented on top of this.

Other protocols which can use ip include AppleShare / Banyan Vines and NFS.

It would be good if a programming implementation could separate the TCP suit
from the IP section so we can bolt more device on and method of
communicating without rewriting the whole lot.

Also a small note most service providers are starting to kick people who off
if you connect to them at 14400baud or less. So if you want to implement
this you'll might want to investigate some other way of connecting

Thanks for Listening
Chris

PS To all those people who are arguing OFFTOPIC on the mailing list please
COOL it or use direct email to discus there point. Also don't force your own
opinion on somebody else.





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