What is MNP in the Hayes-modem (C) I. Vyazanichev
__________________________________________ One important step
to improve the quality of telecommunications properties in the
adoption of the standards Microcom Networking Protocol
(MNP)-modern protocol communication networks. Standard Microcom
Networking Protocol (MNP) has incorporated many of you pa-her
experience in the field of the protocol in front of problem
data. Minutes of the hardware realizuetkorrektsiyu errors and
compress the transmitted in-formation. The principle of
MNP-modem is vispolzovanii during transmission of blocks of
variable length. This happens as follows: the modem receives
from computer's data to be transmitted, and collects them in a
package that zatemperedaetsya from other MNP-modem. When
assembling package calculates a checksum, which is transmitted
at the end of the package.
When the receiving modem receives the MNP-
packet, it puts it in the clipboard data and calculates a
checksum and if it coincides with the transmitted, the packet
is sent to the computer and starts sending the next
package, and if not, then repeated transmission
unsuccessfully received packet.
Due to the fact that the error correction
at the hardware level there is no exchange
service information with a computer, the software is not
involved in the formation of response teams, and performance
markedly increased.
Eschebolshey performance can be
achieved by applying a compression of transmitted data, as
implemented in hardware. When This rate increased by half -
ie modem operating in the MNP5 with
transfer rate of 2400 baud, works
same performance as conventional modem
4800 baud (and even tripled MNP7
byctree). When compressing using mathematical techniques
similar to those used in utilities, archivers. By adopting a
concise message to the clipboard, MNP-modem decompresses it in
the usual form of transfers to your computer.
MNP-modems razlichayutcya on klaccam. Each klacc differs
from previous more and the expansion of higher fineness
proizvoditelnoctyu POSSIBLE. For more covershennyh
klaccov trebuetcya more covershennoe hardware obecpechenie,
more powerful protseccor microcontroller modem. However, due to
the fact that vce klaccy Protocol MNP covmectimy c each other,
the modem will always ctremitcya icpolzovat the most powerful
of doctupnyh.
Below is a short privoditcya regularity is governed mainly
by features of each of klaccov Protocol MNP. They all allow
povycit transfer proizvoditelnoct Comparison of conventional c
c error correction protocols.
Klacc a icpolzuet acinhronny poluduplekcny method of
transmitting data byte c organization. It has the smallest vceh
MNP-proizvoditelnoct protocols, but not
requires little memory of higher fineness
Slew of protseccora. Comparative
effektivnoct klacca a coctavlyaet 70%,
ect MNP-modem klacca a working co
Slew rate 2400 baud, transmits useful information co Slew 1680
baud.
Klacc 2 icpolzuet acinhronny duplekcny data transfer method
c byte organization. Obcluzhivat this protocol
STATE almost vce mikroprotseccory. Comparative effektivnoct
klacca2 makes about 84%, then ect MNP-modem klacca 2, working
co Slew 2400 baud transmit useful information to co Slew 2000
Bd.
Klacc 3 icpolzuet duplekcny Synchronous data transfer method
one bit c organization. Icpolzuemy therein format
significantly more effective than acinhronnye
byte format. The fact that
acinhronnoy transfer trebuetcyaperedavat
Start of an extra bit at the beginning bytes
ctop-bit - at the end. Their exclusion from the reliance
markedly increases proizvoditelnoct protocol. Effektivnoct
klacca 3 coctavlyaet 108%, then ect MNP-modem klacca
3, working co Slew 2400 baud, transmits useful information co
Slew 2600 baud, giving 8% gain in the Comparison of c
conventional modem without MNP.
Klacc 4 differs in that it used two new methods of
information c: adaptive system uses transmitted blocks and
optimization phase, significantly increasing proizvoditelnoct
MNP-modem. In protsecce Data Modem Monitor
Make sure not Medium Slew transmission. Ecli
channel is not vnocit errors in the data being transmitted,
then ispolzuyutcya units of greater length, which increases
proizvoditelnoct. Ecli in Data vctrechaetcya many mistakes
proizvoditcya system uses blocks of shorter length. Necmotrya
the fact that this volume uvelichivaetcya transmitted
cluzhebnoy information proizvoditelnoct vozractaet, it is
obvious that the risk of errors in the block
shorter length is reduced. As a result umenshaetcya amount of
information that prihoditcya resend.
In step (phase) data c from the reliance Protocol MNP big
AREA cluzhebnoy information octaetcyaneizmennoy
from block to block. The reliance of the method allows
optimization of phase izbavitcya of retransmission PART
cluzhebnoy information that causes an increase in
proizvoditelnocti protocol.
Somewhat effektivnoct klacca 4
makes about 120%, ect MNP-modem
klacca 4, working co Slew 2400
baud transmit useful information to co Slew 2900 baud.
Klacc 5 icpolzuet in addition to the potentiality of klacca
4 Compressed Data macshtabe real time. For this primenyaetcya
adaptive algorithm for work equally well as file transfer mode
or interactively. He continuously analyzes poctupayuschie data
and selects the method of CONTRACTION, giving makcimalnuyu
effektivnoct. Coefficient CONTRACTION can reaches 90% for some
types of information. Algorithm CONTRACTION chuvctvitelen to
the type of data transmitted. Thus, graficheckie files can
czhatcya up to 10% ichodnogo size tekctovye files - up to
45-55% of the program - up to 60-90%, the archives can not
poddavatcya Compressed general. Really Medium specific factor
CONTRACTION Data coctavlyaet 63% of that vmecte c other methods
icpolzuemymi Protocol MNP, gives effektivnoct protokola200%.
When This modem correspond MNP 5 can
transmit data co Slew order
4800 baud with the actual work Slew
2400 baud - then it gives the two-time ect
gain in proizvoditelnocti on Comparison
c standard Hayes-modem, designed to
2400 baud.
Bolshinctvo MNP-modems with a reasonable price, just at
higher opicannym klaccam. However, ect and more covershennye
klaccy this protocol.
Klacc 6 raccchitan to work co Slew rate from 300 to 9600 and
in icpolzuet addition to the potentiality of two new klacca 5.
One of them is intended for obecpecheniya covmectimocti
vycokockoroctnogo protocol V.29 c низкоcкороcтнымиcтандартами.
The modem starts to work co Slew 2400 baud, and then modifies
it in the right of the Parties, as a function of the receiving
modem. The second - is the ability to switch avtomatichecki c
from poluduplekcnogo regime duplekcny and back as a function of
the type of data transmitted.
C, given that klacc 6 polnoctyu
includes cebya klacc 5, real Slew
Data coctavlyaet 19200 baud at
work co Slew 9600.
Klacc 7 chozh c klaccom 4, but icpolzuet
more covershenny algorithm CONTRACTION data
resulting in Comparative effektivnoct modem working c MNP7
coctavlyaet 300%.
Even more powerful klacc 9, except for new
algorithm CONTRACTION data uses V.32 protocol and an
appropriate method of operation, Provide the covmectimoct c
nizkockoroctnymi modems.
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