From: lim@merlion.ins.cwru.edu (Hock Koon Lim)
Newsgroups: soc.culture.asean
Subject: Re: modems for BBS  (Long)
Date: 3 Oct 1992 03:52:09 GMT
Organization: Case Western Reserve University, Cleveland, OH (USA)
Distribution: world
NNTP-Posting-Host: merlion.ins.cwru.edu

In article <1992Oct1.141858.17520@ntuix.ntu.ac.sg> eoahmad@ntuix.ntu.ac.sg (Othman Ahmad) writes:
>
>I'm currently using a 2400 bps hayes compatible external modem with MNP 5.
>In Singapore the minimum speed is this one because it is the cheapest
>costing S$90 for internal and $180 for external.
>
   If you want to invest money for a new modem,  I would suggest modem that
support CCITT V.32bis standard.  All most all of the V.32bis modems has
V.32/V.42/V.42bis/V.22bis/V.22 , Bell 212A and Bell 103 features.  This will
ensure your V.32bis modem  "talk" to other modems from 14.4 kbps down to 110bps
if you still can find one to attach to.  Also, most modems in the market today
include FAX support which mean you can turn your computer into a FAX machines.
The price of V.32bis modem range between US$650 to $300.  If this is too much
for you, I would suggest getting the modem that supports CCITT V.32/V.42bis 
standard.  V.32 will give you 9600 bps through put and with V.42bis compression
and error correction, the through put can reach as high as 38.4 kbps( in the
real life, 20 kbps is a more reasonable number).  Some of the V.32/V.42bis 
modems price as low as US$200.  Becareful about sale statement like "provide
transfer rate upto 9600 bps" which usually mean the modem only support 
V.22bis (2400bps) with V.42bis (up to 4 times compression).  These modems cost
as low as us$100.   In the last two years, we have installed about 150 units of
V.32bis modem into our campus modem pools and many other sites has done the
same.  

   As for other modem standard like PEP and HST, they
usually can provide higher communication speed between the same type of modem.
However, these protocols are unable to communicate with other other protocol
or standard protocol from CCITT.  Many of these modems vendors has add CCITT
support into their product lines.

 
>If you want to set up a modem, you are the master, you can use any system or
>speed you want but you must inform the users about your modem speeds and
>protocols.


   The standard is the key here.  If you want to set up dial-in modem 
for BBS system, you want to select a modem that can support as many type
of modems as possible.  If you have modems that support V.32bis standard,
any incoming modems (300 - 14,400 bps) will be able to communicate with 
you.  The only thing the user need to know is the communication parameter
(eg. 8,N,1 - 8 databit, parity none, stopbit 1).

>	In Singapore, I believe the most common speed is 9600 especially whne
>it costs $600 now for the external version.
>	I read in Clarinet that there are versions for 38400 by Trailblazer
>costing US$300 by mail order. Of course, to be able to use at that speed the
>user must have the same brand modem.


  Not quit, I believe the Trailblazer you are talking about is a V.32/V.42bis
modem - T1600.  The 38400 bps is just a theoritical speed in V.32 (9600bps) and
V.42/V.42bis (error correction and compression).
Few years ago, Telebit use their own modem protocol (PEP) in
their modem.  However, they have include CCITT V.32, V.32bis, V.42bis in
their products (eg. T3000 Worldblazer support V.32bis  for about $650). 

>	Make sure the modem also supports 2400 as well.
>Potential operational problems are the signalling protocols for telephones.
>Most modems should be programmable, especially those for export.

  I don't think you can find 1200bps modem from mail order any more.
All our old 1200bps modems have been rest in peace in our warehouse.
Computer users these days can not stand those speed anymore :-). I do
not know much about telephone system in Malaysia but most moderm telephone
system has no problem to support V.22bis(2400bps) modulation at all. With
new error correction standard like V.42 (MNP3,4), it can run very well in
the area that don't have digital phone switch.


>	For the type of dialing tone, the newer exchanges should be using the
>CCITT standard. I'm not sure about US system. Malaysia used to use slightly
>different tones but we have standardised all the exchanges. US should follow
>international standard as well.

   All telephone system in US support Bell or AT&T specification.  However,
the modem protocol has very little relation with the telephone switching 
system except the carrier frequency range.

>If you want your BBS to be available nationwide you may try to use leased
>line maypac. This allows cheap data transfer, especially ones with lots of
>ideal time, for users as far as Sabah. When I make a call, I do not call
>to the BBS modem, rather to a maypac device which can be within my town
>e.g. Sandakan, so that I'm charged for local calls only.

   Building a mesh topology lease line network is not cheap.  Who is paying
the line cost between you hometown and  the BBS?

>	You must use leased line maypac so that you have a maypac address.
>If you only have a dial-up maypac, which is much cheaper, maypac users 
>cannot call the BBS using maypac. This is because the maypac exchanges which
>we had cannot dial out. You can call it but it cannot call you. It must be
>a very old computer and stupid. 

   It sound stupid to me too :-).

>	A workstation should be a better alternative. TCP/IP software can
>do that more effectively since it is also a packet switching system.
  
    If it is an Unix workstation running SunOS or Ultrix, TCP/IP is part
of the OS.  A workstation can provide you the necessary hostpower 
to run the BBS software.  If your BBS is on the Internet, the TCP/IP
protocol can add a lot of advantage to your system.
  If most of your users is dial in to the system with low speed
modem ( 2400 and below), a dump terminal communication software can give
a much better performance then running TCP/IP over the asyn serial link.
All network protocols has overhead.  TCP packet has 40 byte header even
with V.J. compression, you still have about 5 byte or so.  Don't
get me wrong here.  If you have high speed link (14.4 kbps and up), SLIP
or PPP can run very well and provide you the transport of all the TCP/IP 
applications.  There are many great TCP/IP applications software for MacOS,
DOS and unix that user can obtain on the Internet and they don't cost
user any $ to use it.








-- 
Hock-Koon Lim, Information Network services
Case Western Reserve University; Cleveland, Ohio, USA  44106   
(216) 368-2982        lim@ins.cwru.edu