PC Online 1996 October/PCO_10.ISO/filesbbs/hyperp.arj/BULLET4

Text File | 1990-01-06 | 5.6 KB | 100 lines

Bulletin 4 - About MNP modems

The following is a discussion about MNP modems and what they can do for
you in conjunction with HyperACCESS/5.  There seems to be a great deal of
confusion on this subject, which is not surprising.  There is much to be
confused about!  So, by avoiding lots of technical jargon, the following
may eliminate some of this confusion.

Much can be said about the different technical aspects built in to
modems these days.  The are various levels of MNP, V.32, V.42, X.25,
and of course, there are still 1200 & 2400 baud modems that don't
have any of these new features.  Without going into all of the
details associated with each of these technologies, the answers to a
few common questions should clear up most of the confusion.

Before starting the question and answers below, it would be a good
idea to first understand that there are two distinct aspects of a
communications link.  The first is error detection and correction,
and the second is modulation, or the speed at which two modems will
connect.  MNP usually refers to some type of error correcting
features in a modem.  Modulation usually isn't referred to at all,
except in the case of V.32 (more on this later), or in the terms
"High Speed Modem".   Keep this in mind while reading through the
information below.

Question:  Will my MNP modem connect with another MNP modem made by a
           different modem manufacturer?

Answer:    Yes.  When a connection between two modems is established,
           the modems take a few seconds to negotiate common features
           and baud rates.  This usually means that the modem with
           more features will step down to those features found in
           the other.  If both are High Speed modems, an MNP
           connection will be established at a baud rate less than
           what would be considered 'High Speed".  This occurs because
           the error correction scheme used in the two modems is the
           same (some level of MNP for example), but each uses a
           different high speed modulation technique.

Question:  Having a modem that supports V.32 removes the
           incompatibility issues between high speed connections with
           modems from different manufacturers, right?

Answer:    Almost.  The V.32 definition is now a standard modulation
           technique.  This definition includes a maximum baud rate
           of 9600.  So, modems from different manufacturers that
           support V.32 will connect at a line rate of 9600 baud.
           Although 9600 baud is a vast improvement from 1200 and
           2400 baud connections, it is still slow in comparison to
           the proprietary modulation schemes that can be used when 2
           modems of the same type are used.  Also, the V.32
           definition does not include error correction.  This means
           that a V.32 modem (in most cases) will still use some
           other technique, usually MNP, to achieve its error
           correcting.

Question:  I want the fastest file transfer throughput possible for my
           application.  What type of modem should I buy?

Answer:    If you are able to use HyperACCESS/5 on both ends of the
           communications link, you already have part of the
           solution.  HyperProtocol is the FASTEST file transfer
           protocol available for asynchronous communications.  The
           second part of the solution involves establishing the
           fastest possible connect rate.  To achieve this, you will
           want to use a pair of the many high speed modems supported
           by HyperACCESS/5.  Take a close look at HyperACCESS/5's Modem
           menu for a list of these modems.

Question:  I have an MNP modem that has data compression built in.
           Is this going to conflict with the data compression used
           by HyperProtocol?

Answer:    No.  Your modem that uses data compression does not know
           that HyperProtocol is compressing data too.  Likewise,
           HyperProtocol doesn't know that the modem is using data
           compression.  They will not interfere with one another.
           Remember, however, that HyperProtocol's data compression
           is doing much more to increase overall throughput than the
           modem's data compression.  Why?  Because HyperProtocol has
           already reduced the amount of data BEFORE it gets sent to
           the modem.  Without HyperProtocol's data compression, the
           ENTIRE amount of data gets sent to the modem and then it
           gets compressed.

Question:  Will I achieve faster file transfers if I use ARC, PKARC
           or some other data compression utility before I transfer
           files.

Answer:    No.  HyperProtocol's dynamic data compression will shut
           down if it determines that data cannot be compressed.  The
           throughput after such a transfer will in most cases be
           identical to the throughput had you not compressed the
           data prior to the transfer.  So, there is more work
           involved in processing the files, both before and after
           the transmission, when using data compression utilities.
           The same net result can be achieved without the pre and
           post process of compressing (or arching) prior to the
           transfer, and decompressing (or dearching) after the
           transmission.