home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Tech Arsenal 1
/
Tech Arsenal (Arsenal Computer).ISO
/
tek-20
/
tn210.zip
/
NETWORK.EXE
/
NET-1.TXT
< prev
next >
Wrap
Text File
|
1992-06-04
|
4KB
|
72 lines
NET-1.TXT
NETWORK IMPROVEMENTS
--------------------
With exception of a few areas, most network development in the country has been
a haphazard process. A point has been reached where an integrated network
plan that's agreeable to all users and servers needs to be put forth so as to
lay out design goals for future network growth.
Early packet publications had numerous articles describing the inefficiency
of a simplex network. Simplex by its very nature suffers a loss of up to
50% in data throughput right off the top. This is because the receiver
and transmitter shares the same frequency and one has to wait on the other
before operating.
In a string of digipeaters, further throughput delays occur when one or more
of the simplex receivers detect packets from elsewhere and holds off its
transmitter until the frequency is clear. An example in Arizona is the node on
Mt Lemmon. LMN hears the CANSON, JACKS, NOG, SVA, SVASW and BISBEE nodes, all
on 145.01. LMN additionally hears several BBSes as well as many on-channel
users. Even with a lightly loaded network, delays are noticeable until the
frequency at LMN is clear. Is it any wonder 145.01 comes to a near halt when
activity picks up?
-------------------------------------------------------------------------------
NODE NODE NODE NODE NODE
A <145.01> B <145.01> C <145.01> D <145.01> E
users users users users users
Simplex network hears as a minimum, traffic from adjacent nodes, thus holding
off local user packets until the channel is clear. Quite often, packets from
two or more nodes away is heard, with resultant reduction in throughput.
Figure 1-1
-------------------------------------------------------------------------------
This situation improves somewhat when a simplex backbone trunk is installed.
Initially throughput is improved since most of the users are left behind on
the LAN channels. But usually the backbone nodes still hear more then one
of their neighbors which causes throughput to suffer. After awhile, some of
the high volume users will decide they have better service if they directly
access the backbone. This adds more transmitters that adversely affects the
backbone receivers, thus slowing network activity. After a time, the network
with a simplex multi-user access backbone trunk is only slightly better off
than the original primary simplex circuit.
-------------------------------------------------------------------------------
NODE NODE NODE NODE NODE
#A <441.6> #B <441.6> #C <441.6> #D <441.6> #E
A B C D E
144.97 145.09 145.01 144.95 145.05
users users users users users
Simplex backbone trunk with solated LAN nodes for user access. Eliminates
interference between LAN nodes and improves local traffic throughput. However
basic "simplex problem" is now transfered to the backbone trunk.
Figure 1-2
-------------------------------------------------------------------------------
What's good about a simplex network? Simplex does have advantages. It's
cheap, easy to install, and works reasonably well under lightly loaded
conditions. As many have observed though, simplex falls apart with increased
channel usage.
It's possible the disadvantages of a simplex network can be turned to an
advantage of sorts by analyzing its weaknesses and coming up with ways to at
least partially off-set the problem areas. Furthermore, some of these
techniques can be used to good advantage on more sophisticated network
systems.