Shareware Supreme Volume 6 #1/swsii.zip/swsii/201/IO1093.ZIP/FTUR02.TXT

Text File | 1993-09-30 | 9KB | 196 lines

                    Connecting 9600 and Beyond

                           Chip Morrow


  Free advice, and "For what it's worth" department:

  I have been asked about 9600 BPS and beyond more times than I
  care to think about, so the time has come to sit down and write a
  bit on this subject. If you are the least bit interested in
  upgrading to 9600 or 14400+ BPS, you might find this interesting.

  The only way to talk about this is via a history lesson of 9600
  BPS as I see it.  Just some observations:

  Many moons ago, the CCITT v.32 standard was not in use by
  anybody, as it was deemed to be too expensive to realistically
  build hardware to support the as-yet-unused international
  standard.

  Modem manufacturers retaliated by building their own proprietery
  9600 connection schemes, and the next thing you knew there were
  modems all over the place that wouldn't talk to any other brand
  at 9600 and beyond.

  (If you bought a CompuCom 9600, you had to find another CompuCom
  9600 to connect to if you wanted 9600 BPS operation.  Etc.
  etc...)

  As connect speeds increased, so did errors in data transmission.
  Anyone who has ever used a "standard" modem of the 1200 or 2400
  BPS variety can verify that you do occasionally experience line
  noise, which shows up as a burst of incomprehensible characters
  on your terminal.  A 2400 BPS modem does not use NEARLY the
  bandwidth that high-speed modems do, so you can imagine what
  happens with one of these when you experience line errors.

  That's why "error correction" and "data compression" are built
  into the hardware on most of these things. We'll talk about THOSE
  in a bit here.

  Before all settled down, the one that rose to the top of the heap
  in the BBS world was USRobotics, with their proprietery HST
  modulation scheme, which is still in use on MANY bulletin boards
  today, including 1 node here.  USR is still widely accepted in
  the BBS community as the leading manufacturer for BBS-compatible
  modems, but there is a price to pay (more on this in a minute).
  USR has since upped their proprietery HST protocol to 14,400 bps,
  and most recently 16,800.  Problem is, you NEED a USRobotics
  modem to talk to them at that speed.

  USR does manufacture the "ultimate BBS modem" from my viewpoint,
  and that is the USRobotics Courier HST Dual Standard, supporting
  both their HST line, as well as the CCITT v.32 and v.32bis
  standards.  With one of these modems, you can connect to
  virtually any bulletin board in the country at 9600 and beyond.

  Perfection has a price, however.  The new Dual Standards are
  retailing for over $1,000 apiece (although they can be had for
  $700 or so thru direct channels).  A little pricey from my
  standpoint.

  Which brings us back to v.32 and v.32bis.  These are the accepted
  international standards for high-speed modems, and they are only
  just recently becoming widespread, and supported by MANY modem
  manufacturers. Virtually every modem manufacturer EXCEPT
  USRobotics has devoted their high-speed lines to the CCITT v.32
  and v.32bis modulation schemes.

  Now, back to error correction and data compression. You're likely
  to have heard terms like MNP levels 1-5, v.42, and v.42bis.
  Strangely enough, NOT ALL HIGH-SPEED MODEMS SUPPORT THESE.  I
  have seen some low-end v.32 modems that will connect at 9600 BPS,
  but with no error correction, meaning that your high-speed
  connections will be unreliable at best. Let's talk about these
  terms for a bit:

  MNP = Microcom Networking Protocol.  There didn't used to be any
  standard for error correction/compression, and Microcom's  imple-
  mentation gained wide acceptance pretty quickly. Most modems that
  support error correction support MNP.  There are several "levels"
  of MNP built into many modems, even more than I'm going to bring
  up here, but here's what a few of the more common methods mean
  (briefly):

  Levels 1 through 4 = Error correction.  The modems negotiate to
  the highest-supported level on both ends, and errors in
  transmission are "filtered" before they get to the remote
  terminal.

  Level 5 = Data compression.  If "compression" is turned on on
  BOTH ENDS of the connection, and both modems support MNP-5, the
  modems will negotiate to this type of connection.  Theoretically,
  this can increase throughput on file transfers.  But, in reality,
  90% of the files you transfer are already compressed (ZIP, ARJ,
  LZH, etc.), so the overhead of this protocol will actually slow
  you down.

  V.42 = Here comes the accepted international standard for error
  correction.  It is generally felt that v42 hookups connect
  quicker and more efficiently than their MNP-4 equivalents. Most
  modems supporting V42 will "fall back" to MNP-4 if a v42
  connection couldn't be made, and to no error correction if both
  fail.

  V.42bis = ...and here's the international standard for data
  compression.  It is generally felt that v.42bis performs better
  than MNP-5, especially on noisy lines. Most modems supporting
  v.42bis will "fall back" to MNP-5 if a v42.bis connection
  couldn't be made. v.42bis is more efficient than MNP-5, and you
  will usually see higher throughput than with MNP-5. However, this
  method can STILL actually slow you down when transferring
  compressed files.

  Things to remember:

   You're always limited by the phone lines in your
    area.  If you get static on the line when you make a
    voice call, you can amplify that several times over
    when you make a high-speed connection.  9600+ uses
    just about all of the available bandwidth.

   ERROR CORRECTION is a must.  DATA
    COMPRESSION really isn't, although one tends to
    come with the other on most modems these days, and
    there are quite a few people who will tell you that
    you NEED v.42bis.  I have always seen the best
    transfer speeds with error correction on, and data
    compression off.  The one exception is if you transfer
    a lot of text and/or data files that are NOT already
    compressed.  In that case, data compression really can
    speed up your transfers considerably.

   Most any 9600 BPS modem (including the HST)
    will connect with any other high-speed modem at
    2400 and below.

   USRobotics' HST, like any other modem using a
    proprietery scheme, will connect 9600 and beyond
    only to another USRobotics HST modem.

   USRobotics' HST Dual Standard (the pricey one)
    will connect 9600 and beyond with both their own
    HST's, as well as v.32 and v.32bis modems (which is
    just about the whole high-speed market).  This works
    the other way, too, of course.

   Any modem supporting v.32 should connect 9600 to
    any other modem supporting v.32 (from various
    manufacturers).

   Any modem supporting v.32bis should connect
    14400 with any other modem supporting v.32bis, as
    well as 9600 with v.32 modems.

  My advice:  Stay away from oddball 9600 modems that won't talk to
  anything but other modems from the same manufacturer.  USR's HST
  has a strong foothold in the BBS market, but that foothold is
  dwindling.  v.32 and v.32bis are increasingly becoming the way of
  high-speed for the  future.

  Go 14,400 BPS v.32bis, but be careful.  Real-world pricing for
  low-end v.32bis has dipped under $300 apiece (closer to $200 on
  some internal models) from several different manufacturers (Zoom
  and Boca, to name but a couple).

  If you have a large wallet, get a USRobotics HST Dual Standard
  (*NOT* the cheaper HST model). They are very good, reliable
  modems, and most communications & BBS software have setup info
  for them.  They were simply too expensive to be a practical
  option on this end.

  Make sure your system can handle the speed before you buy.  You
  should have at LEAST a 10mhz machine (preferably a 286 or
  better), and at least a 16450 UART on your serial port, or you're
  likley to start dropping characters.  If you're in a
  multi-tasking environment, or you find yourself dropping
  characters, you'll need a 16550 UART (which has a small built-in
  buffer to help out with this problem). Insist on error correction
  of some type, either MNP-4 or v.42.  Otherwise, the line noise is
  likely to make life miserable for you.  You'll likely also
  receive data compression with your modem, since one tends to come
  with the other.

  If you aren't transferring text files, turn off data compression
  (MNP-5 and v.42bis) for maximum throughput on compressed files
  like .ZIP, .ARJ, etc. There are people who will tell you that
  you'll do BETTER with v.42bis enabled, but that hasn't been the
  case in my experience thus far.

  BE WARY OF USED v.32bis MODEMS FOR A WHILE.  Rockwell put out a
  bad set of the v.32bis chipsets a while back, and modem
  manufacturers are putting out updated ROMs for these modems at a
  bizzare rate.  You want to be able to return the modem if it's
  broken.