A guide to..
..alternative networking!
By Kei/Carnage
I'm in the middle of my 2nd year degree exams at present and I've just
sat my Networks and Communications exam when I take a break from
revision to edit some articles for The Word and reach D!ck's article on
Networking.
This article comments on D!ck's article (so read it first) and gives
you some (cheap) alternatives to linking machines that some of you may
know about and some may not.
First off, the LAN configuration that D!ck was talking about is a "BUS
type Thin Ethernet" type LAN setup which uses NIC (Network Interface
Cards) slotted into your PC which have a BNC "T-type" connector on the
back which connects to LAN cable (50ohm) segments together. At the end
of each end of the network is another connector known as a "terminator"
which is essentially a resistor designed to absorb signals thus
preventing bounce-back. This type of LAN has a size limitation of 185m.
There are other LANS such as TREE, STAR and RING which use different
protocols. Ehernet LANS use CSMA/CD (Carrier Sensing Multiple Access
with Collision Detection) and the Medium Access Protocol (MAC) to send
data frames down the line (boring stuff concerning encapsulation and
synchromization which I won't go into).
D!ck said he didn't understand the concept of a terminator in his
article. Basically, the time it takes to broadcast a message from one
end terminal to another and back again is known as the "Slot Time". If
a collision has occured then a Jamming Signal is sent to prevent any
other terminal from transmitting for a pre-set time before trying again
(known as 1-persistant). If there are no ends to a cable segment then
when a signal reaches the end of a cable, it wraps around and comes back
(bounces back), meanwhile another station has checked that the line is
idle and has transmitted a packet onto the cable which collides with the
bounce back. All the terminator really does is absorb the signal. To
understand it more clearly, each terminal "broadcasts" a frame of data
onto the cable and as it passes through each machine on the cable (in
both directions) they read it to see if it is addressed to them. If not
they ignore it. It then at some point reaches the ends of the cable and
must be removed to prevent being bounced back otherwise you'd get
nothing but bounce-backs forever on the cable producing noise.
Entire streets could be networked D!ck, as long as they don't exceed
185m. You can use bridges, repeators and even microwave links (and I
don't mean to cook dinners while playing doom!). It get's long winded
at times though and the only reason I know so much about networks at the
moment is because it is part of my degree and my job in Ipswich is as a
network technician and support staff. Maybe I could write some articles
in future issues about networks but it would be stuff like "Network
Sniffing", "LANS, WANS to DNS", "Intranets" and "TCP/IP" so if any of
you readers are into that sort of thing then let me know!
10Mbps/s is about right for CSMA/CD however the 2nd generation LANs
such as FDDI can handle ten times that!
If anyone does have any questions on networking or anything else you
can send them in to our new Q&A article that we are starting soon where
the Word staff will endeavour to answer ANY readers questions!
Where was I?....
LANS are all well and dandy but what will you do if you have different
computer types and different peripherals that are incompatible? After
all The Word readers don't all have PC's do they? Of course there are
Amiga networking solutions out there at present but that's not what I'm
going to suggest here.
At present in my room I have 3 computers connected together. There is
my A1200, my PC tower and my PC laptop. Connecting the PC's together is
a simple matter of using a parallel cable and Windows 95's DCC software.
But what about the Amiga?
Since I gave out my email address in a previous issue of The Word,
several readers have emailed me asking "how do I connect my Amiga to my
dad's PC to copy files across?". I've told them how but to save me
typing it again and again I'll tell you how I do it.
PC to Amiga
You can use either a serial cable (not null-modem as it's too slow) or
a parallel cable to connect your Amiga to a PC. If using a serial cable
then I recommend Twin Express which is available from the aminet in the
comms directory. This will give you an average transfer speed of
115,200bps (7-wire cable). If using a parallel cable then I suggest
PC2Amiga which is also available from the aminet. I think the file is
called "PC2Am308.lha".
Setting up these programs couldn't be easier. Just unarchive the
archives and copy the PC files to your PC (use floppy). Then install
them on both machines, choosing identical setups. If using Twin
Express, type TWIN COM2 on your PC and TWIN SER on the Amiga and then
type HELP COMMANDS to get going on either machine.
If using PC2Amiga, you can run "PC2Amiga" on the PC which gives control
over to the Amiga so you can turn your PC's monitor off. Your Amiga
should now have a drive listing like: DF0: DF1: CC0: DH0: DH1:
DH2: RAM: A: C: D: E: . If however you type "PC2Amres" then this
runs a version of the previous program which lets you continue to use
the PC with PC2Amiga acting as a resident program.
The solution I use is I boot the tower as a server machine. I then run
an MS-DOS window from Windows 95 where I run PC2AmRes. I then setup
PC2Amiga on the Amiga so it can detect the towers drives and
peripherals. Going back to Windows 95 I either use LAPLINK or DCC to
initiate a setup with my laptop via parallel cable. Once all 3 machines
are running (and my dad's moaning about the electricity bill), I can
transfer files till my hearts content.
A typical reason for me to do this is I've downloaded about 10 HD
floppy disks worth of goodies from the Aminet at university as well as
some PC software and I wish to transfer the Amiga software to my A1200
which does not have a HD floppy drive. Or when writing web pages on my
PC's I prefer to use the Amiga for image creation and to convert IFF to
GIF or JPG then I'll transfer the files to the PC's for
testing/formatting purposes.
LANS are a good idea for PC users but for us Amiga guys with maybe one
PC, we need to use cables. If connecting Amiga to Amiga though you
can't go far wrong if you use PARNET and a parallel or parnet cable.
The best ad-hoc setup I've come across was at the last internal Carnage
party where we had 2 Amiga's hooked up with Parallel cables and two more
Amiga's connected to them via 7-wire serial cables so we can transfer
files across several machines. We used that setup to complete The Word
issue 13.
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