#MNP Modems
28 messages in this thread
?
I'm shopping for a new modem. I've been seeing quite a few ads for 2400
bps modems featuring something called 'MNP Level 5'. I know it's some kind
of error checking but I haven't found anything explaining it. My main
questions are:
1) Is the error-checking in hardware or software?
2) Does it REALLY run at 4800 bps in this mode?
3) If it does, what are it's limits? Do is it have to be connected to
another modem with the same feature, or will it work with any
connection?
4) Does it boost the speed of file transfers only, or all communications?
Will it work at 4800 bps with Amiga games such as Falcon & Populous?
I need a modem that will work with both my Amiga and a Messy-DOS machine. I
would appreciate any suggestions for modems along with answers to my
questions.
Thanks,
Richard
Richard,
A 2400 bps modem using MNP Level 5 compression/error checking will transfer
data to another similarly equiped modem at an effective transfer rate of
4800 bps under ideal conditions (absence of line problems). If the remote
modem is operating at 2400 bps without MNP, then the transmission rate will
be at 2400 bps (maximum). I believe that Compuserve has MNP 5 capability. I
had the chance to transfer files between two computers using MNP 5
(essentially 'hardwired' modem to modem) and the data throughput was indeed
4800 bps. The small difference in street price between 2400 bps modems with
and without MNP 5 makes the MNP version well worth the extra money (usually
$150 vs $120).
Rich
Chowdy Richard,
CompuServe does not support MNP 5 according to my last check with them.
There is a good reason for this. MNP level 5 uses a compression method
similar to ARC and LZH. Since most of the files transferred using CIS are
already compressed, recompressing them using MNP 5 doesn't gain you much in
the compression process and when you add on the added handshaking and data
bits for the protocol you actually increase the size of the file. For text
only transfers (reading information out of display pages like Online Today
or the new NASA area, for instance) would be faster. But these areas don't
comprise a particularly large area of usage.
I you want to use MNP level four, I believe you need to append a /Level 4
command to the end of your user number. I have tried using the MNP switch
in Whap! with the Baud bandit modem and it worked fine for me.
Chow, Cheryl P!
Chowdy Cheryl,
Chowdy?
Thanks for the info. I read a message here a few days ago that MNP 5 was
being used on CServe. Guess I (or that message) was wrong.
Rich
Chowdy Rich,
Chowdy is my own personalized greeting. The explanation is a little long,
so I'll forego it. Just take is an especially friendly "hiya."
The only reason I know anything at all about MNP is that I just did a
review of the Baud Bandit modem and I needed to know more about it to do an
accurate review. Normally I avoid learning too much techie stuff as I
think it distances me from the normal end users. CIS does support MNP but
only up to level 4, as I understand it.
Chow, Cheryl P!
Rich,
Thanks for the info. Sometimes it's hard to tell what is real anymore
and what is 'marketing'. Do you have any brand of modem you would
recommend? I'm still using a 1200bps Commodore 1680 modem for my
telecommunications (on a C-128) and want to learn as much as I can before
investing in another one.
Thanks,
Richard
Richard,
Sorry, I can't recommend a specific 2400 bps modem with MNP. I CAN
recommend a non MNP modem however – the Supra 2400 zi (internal) modem for
the Amiga. This is a beautiful little piece of equipment. It is the most
trouble-free modem I have had. Supra seems to be a very dependable outfit.
They are going to have an MNP external modem (2400 bps) in a few months,
but according to their tech support line, no MNP internal modem.
Rich
Richard,
I have a Practical Peripherals 2400 MNP Level 5 modem and really like it.
Of course, it is the only MNP modem I've ever used, so I cannot compare. I
do like the fact that they have their own forum on CIS to support their
products, and you can get LOTS of help from them.
……Betty
Thanks for the info. I was leaning toward a Supra 2400 before learning of
the MNP feature. I need an external one because I need to be able to use
it with an Amiga and a PC machine. I hear they have (or will have) a Supra
2400 Plus which has MNP. I am however open to ALL suggestions.
Thanks,
Richard
Richard,
I really like the one I got – Practical Peripherals. They have a forum
here to offer support, too – GO PPFORUM
……Betty
Betty: I live in Alaska and experience a lot of noise problems. What
benefit can I expect if I purchase an MNP modem. I currently use a Supra
2400 external. Also, should CIS go to MNP 5, what overall benefit would
that have for ASCII as well as binary transfers. Will I actually be able
to transfer at 4800bps even though our telephone lines are 2400bps. What
is the fastest transfers that CIS will handle? Thanks.
George
George,
I suspect that you would get a more complete answer to this on PPFORUM,
where they support the MNP modems they sell. I can tell you that I had
very noisy lines, with constant garbage instead of data, before I got this
modem and got it set for MNP. I don't think I'm getting any speedup of
transfer, since CIS is using MNP level4, and that level does not do the
compression. I don't have noise problems any more, though. Once in a
while, when the lines are at their worst, I get cut off, but I never see
the garbage characters any more.
If you can connect with another MNP Level 5 modem, you get data compression
and that does give you nearly double (probably not quite) the rate, so that
would be close to 4800.
Currently, almost all of the CIS modems are at either 1200 or 2400. I
believe they have done some testing with 9600 b, but that speed is not
offered to us, so far as I know.
……Betty
George,
I don't live in Alaska, although it sounds nice u there, and still get
plenty of garbage. Lately about 50% of messages have a little garbage in
them. Oh, I live in Columbus, Ohio, right across town from CIS!!
Mike,
Mike: It is nice up here. All the snow is gone where I live and we're
enjoying clear sunny weather in the 60's. It's still icebound in Prudhoe
Bay where I work however, and will be for another few weeks. I've noticed
something interesting. I just joined Peoplelink. I logged on directly
through their Chicago node and had a great connection. The data really
screamed in. Unfortunately, their protocols are limited (WXModem is their
best), and they don't have any automated term programs like Whap!. I
logged on 4 different times and had good results each time. No file
waitings either. I'm going to try logging on to CI$ via Seattle and see if
I get a better connection than from Fairbanks (100 miles away). BTW, I can
call Chicago or Seattle or just about anywhere in the lower 48 cheaper than
I can call Fairbanks. I just found that out. Rediculous isn't it?
George
Richard:
I went with a Supra 2400zi, and don't regret it! Because it's an internal,
they supply a device driver, so that free's up the serial port for other
things. Also, I've found a few programs that were sort of buggy when used
with the serial.device fly right on Supra's Modem0.device.
-Mike Schiller
CIS: 76416,3065
Richard,
The benefits of an MNP modem are many, especially if your phone line is
subject to occasional fits of noise.
Make sure that the MNP error correction is done in hardware, the software
versions of this mode do not do it justice.
Although an MNP modem must be connected to your computer at a baud rate
that is higher (usually two or four times) than the connection rate in
order to have a gain in throughput, it will never achieve the 4800bps rate
that the marketroids like to claim for these things.
The two most common levels of MNP today are 4 and 5. Level 4 provides a
solid 17% perfomance gain by stripping the start and stop bit for each
character transmitted. Level 5 adds data compression to the picture, for
text only transfers, the performance gain is incredible. But for most file
transfers with a protocol such as ZMODEM, it can actually degrade
throughput due to archived binary files usually being the object of the
transfer.
Average speeds of an MNP level 4 ZMODEM transfer can range between
250-270cps, depending on the data in the file.
Text will look somewhat choppy in the way it is received with level 4.
With level 5, a full screen of text can sometimes pop up, but it too will
usually have a choppy look to it. Some people find it a bit disturbing to
look at at first, but the lack of "modem puke" (noise) far outweighs the
disjointed appearence of text output.
An MNP modem requires CTS/RTS (7 wire) handshake in order to work without
data loss, I don't think games that have a modem mode are sophisticated
enough to provide this, although I may be wrong on this, I'm not a gamer.
As for actual brands, I can recommend the MultiTech 224EH, although it is
a good deal more expensive than most others available today, it is one
solid product.
If your budget allows and you plan on doing a decent amount of long
distance calling, I'd have to say the 14.4kbps HST is the most economical
modem in the long run. Not only does it fall back to standard 2400bps with
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MNP level 5 when needed, it will provide throughput of over 1650cps when
connected with another 14.4kbps HST. It is also the most common modem in
use by IBM BBS systems, so you won't be starving for places to call to.
-jack-
I appreciate the information, Jack. It would appear that MNP does make a
difference. I was a little disturbed to see that it degrades thoughput
with some protocols. Under these cases I would imagine it would be best to
drop back to standard transfer speeds, right?
As much as I would like to have a 14.4kbps modem, there's a lot of other
hardware I'm looking at now too (ie. hard drives, RAM expansion,
accellorators, digitizers, etc.) so I think I'm going to go with a 2400, at
least for now. I just wanted to make sure it was worth it to get one with
MNP.
Another question: will the modems with Level 5 also work at Level 4 or
are they mutually exclusive?
Thanks again for th}ie}i }ixD{_=
info.
Richard
Chowdy Richard,
If the Baud Bandit modem is typical of MNP modems (and from the way the
documentation is written is written, I think it is) the modem defaults to
level 4. If you want to go online at level 5 you must set it before you
make contact with the modem at the other end. This is fairly easily
accomplished with the Baud Bandit, so I think it would be easy with most
others. The hardware is usually pretty simlar on these kinds of things.
Chow, Cheryl P!
Cheryl,
Ok. Understood. I'll just continue to use my Supra zi for a while. No MNP.
Works fine. Hope an internal MNP modem comes along! :>
Rich
Cheryl,
The Practical Peripherals modem (and I think most MNP modems) can be set by
a command to nonvolatile memory. I have mine set to auto-reliable. This
means that it will try to establish MNP level 5 contact. If that is
impossible, it falls back to level 4, and if THAT fails, it tries a
standard Hayes connection. It works fine. If the RELIABLE is achieved, it
tells me so in the CONNECT string. From my reading on CIS, I believe this
is the standard method.
……Betty
Betty,
Thanks! I'll add that to my MNP modem info for the next review I have to
do.
Chow, Cheryl P!
So, it appears that the MNP L-5 WILL drop back to the other protocols!
That's good to hear. It sounds like there may be a bit of playing around
to do. What's new, huh?
Thanks,
Richard
Richard,
MNP level 4 is a win in any situation, if only for the elimination of
noise. It's level 5 that can bite you if you're going to do a binary
transfer at some time during the connection.
The way I recommend setting up you comm program with an MNP modem is to
have three dialing prefixes, one that enables just level 4, another that
enables level 5, and one that disables MNP altogether. The reason you may
want it disabled is for times when you're calling a real Hayes 2400 modem,
you'll know because the MNP handshake sequence that is sent when a
connection is first established never fails to lock up the Hayes modem.
You'll be connected, but you'll never see anything from the remote system.
The other two dial prefixes can be used to call systems where you will or
won't be doing binary transfers. You'll want to leave level 5 for text
only calls due to the degradation that level has with binary transfers.
Also, you may want to engage level 5 for the first call to a system to
determine which MNP level the connection is established at, it will fall
back to level 4 if a level 5 connection can't be made.
The one thing in this case is to make sure that the modem is in a mode
that allows auto-fallback to a lower MNP level or to a regular 2400bps
connection. This may sound easier than it really is because some MNP
modems out there can have an unbelievable number of parameters that you can
dink with.
Although the HST 14.4kbps is a good chunk of money, it will pay for
itself very shortly if you plan on doing alot of transfers. For casual
users it probably isn't the right choice, or if you don't plan on doing a
whole lot of long distance calling.
-jack-
Jack,
Thanks for the information. It looks like experimentation is the key.
Can you tell me at what speeds the HST 14.4kbps modem runs? I want
something that will be compatible not only at 2400bps (MNP and oth
occasionally I still need to be able to go at 1200 (at least locally).
As much as I would rather NOT spend the extra, you may be right that it
would be worth it.
Also, I am still interested in a modem to use with these great modem
games that I can't wait to play. I guess I could go ask somebody from
Spectrum Holobyteat requirements are needed for Falcon. They should know
if anyone would.
Richard
Richard,
The HST is compatible across the board from the lowly 300 baud modem up
to 2400bps (with or without MNP levels 4 & 5). It uses a proprietary
method for 9600 and above, so those are only compatible with like modems.
The dual standard also includes v.32 full duplex 9600bps which is gaining
popularity quite fast as the accepted standard for 9600bps, but it is a
very expensive addition to the core HST (and is quite bit slower than the
14.4kbps mode).
They may or may not have added v.42 error correction and compression as
of yet, this is an alternative to MNP and is in use by Hayes and a few
other modem manufacturers now.
MNP is a complex addition and really does require a bit of
experimentation in order to tweak the modem for maximum throughput, but it
is definately worth the effort in my opinion. For those with noisy lines
it's an absolute must these days.
-jack-
Richard,
I'm using a Practical Peripherals 2400baud MNP modem, and it has been most
helpful to me. It works best when it can connect to another MNP modem, but
can connect to others. You do lose many of the benefits when the other
modem is not MNP capable, though – especially the faster throughput.
1. If the modem is listed as MNP, then the error checking is in hardware.
It is possible to emulate this in software, and this is done in a few
cases, but it is not as satisfactory, according to my reading.
2. If both modems are MNP level 5, then there is data compression and you
really do get the data much faster. If only one is MNP capable, this does
not happen.
3. The biggest benefit of MNP for me is that it screens out the line noise
that was constantly plagueing me. I never see those stray characters on
the screen any more, and I get more accurate transfers. My phone line is
particularly noisy, and this has been a real benefit to me.
4. Sorry, don't know about the games.
……Betty
Betty,
I have a LOT of line noise, so it looks like MNP is definitely the way
to go. Anything that would help in that respect would be most appreciated.
Richard