Welcome!
to the Modems section
This section is probably of most interest to owners of V.90, K56Flex & X2 modems who are tearing their hair out because they are the proud owners of 56k modems that simply will not connect at 56,000 bit/s. Once again, there is much below that will be of interest to all modem users.
| In 1998 - if you believe what each company says - Rockwell Semiconductor Systems and US Robotics both won the commercial war that they had been waging against each other in the previous year for the new standard in modem telecommunications. The reality, of course, is that modem users lost & are still suffering the collateral damage now, more than a year later. Brief explanation: In February 1998 the ITU introduced V.90, a new internationally-agreed standard for modem-to-modem communications that promised 56,000 bits-per-second [bit/s] downstream-rates and 33,600 bit/s upstream rates; this standard was ratified in September of the same year. Now, what you have just read is already untrue and part of the hype that always surrounds these things. 56k bit/s and 33.6k bit/s are theoretical maximum downstream/upstream rates and almost never achieved in practice - indeed there are people that will never ever achieve even the maximum upstream rate in either direction, but more of this later. Before V.90 was introduced the various chipset manufacturers had attempted to use their commercial muscle to enforce mutually-incompatible and proprietary standards developed by themselves - see boxes at right. This latter situation had led to ISP's having to have multiple dial-up lines - one for K56Flex™, one for X2™, one for ISDN and another for previous standards. V.90 now promised to do away with all of that nonsense... eventually. |
A Little History
|
|
The situation now: Modem chipset manufacturers and software writers are desperately trying to produce silicon and software drivers that conform to the standard, and succeeding, more or less. The situation is compounded by many things. Any of the sections detailed at left would make life difficult; put them together, & it is a miracle that any modem connects at all. As one example, your modem - which is more-or-less compliant with a standard - has to connect with the Headend Digital Modem - which is more-or-less compliant with the same standard. Get the picture? |
| V.90 As long as you do not mind being led by a one-eyed man, on the right is as untechnical an explanation of V.90 as I can manage. As a non-telephone engineer I'm grateful to Alan Fowler for his input on this. A more technical description from Alan is here. V.90 performs it's magic by assuming that the network is digital on the downstream side and voice-band on the upstream side. Now, I know, I know - why not assume that it is digital both ways? but that's how it is, so try to live with it or get an ISDN link. The ISP has a direct digital link to the main exchange and thus one of the conversions is absent, reducing potential errors and increasing the maximum potential speed at which communication can take place. Notice, however, that word 'potential' - other factors on the line can reduce the actual practically-achievable speed, & this leads nicely into the next section: |
|
| Getting better connection speeds First, a quick bucket of cold water (called reality) for owners of 56k modems - you will never achieve connection speeds of 56,000 bit/s, not ever, and any speed over 33,600 is a 56k connection. | What can you do...? |
||
| Another initial question, of course, is 'What speed is my system connected at?' The easiest way for Windows' users to find the starting connection speed with a dial-up line is to hover the cursor over the little icon sat in the system tray after connection (see panel right). This icon looks like two computer screens connected by a line and belongs to Dial-Up Networking [DUN]. As with all things in life, DUN can lie. |
|
|
DUN shows 57,600 or 115,200 bit/s then the modem's .inf file is either the wrong one, or inaccurate, & DUN is reporting the DTE speed rather than the DCE speed - go here for more information. If the .inf file is the correct one then go to Extra Settings and enter one of the strings as at left. Even "correct" INF files are sometimes incorrect The last string in the list at left sets the modem to factory-defaults. Unfortunately even this desperate measure will not work for some modems, & one reason may be that the Responses section of the .inf file is missing such as the following (from my own modem's .inf file):-
[MfgAddReg] Now, whilst K56Flex is in steps of 2,000 starting at 28,000 & finishing at 60,000 bit/s, V.90 is in steps of 1,333, leading to some very strange connect-speeds indeed. If the .inf file is missing any of these speeds then the computer may default to show the DTE speed. If you are determined to correct this terrible error then it means either hacking the .inf file & re-installing the modem and/or hacking the Registry direct. With my modem this is:-
System CurrentControlSet Services Class Modem 0000 Responses |
||||||||||||||||||
| DUN takes a long time to connect Whilst this is the speed of connection rather than the connection speed it seems to be very common. What follows is specific to Freeserve but may have relevance for other ISP's, particularly if you also have AOL. The typical picture is of dialling out with long, long periods of hand-shaking but no connection with an eventual time-out resulting in the whole process being repeated over again, perhaps many times, until connection is eventually made [or not]. Whilst there is excellent help on the Freeserve support pages here is a quick troubleshooter for this one:- Check the Network & DUN settings A screen shot of the minimum Network entries needed is here. Unless your setup requires other network-facilities any others should be removed. Do not change settings in entries here unless you know exactly what you are doing - changes here over-ride those in DUN with no warning. Indeed it may be worthwhile to follow instructions on the same page as the screen-shot to remove & re-install DUN and thus the dial-up adaptor & retrieve your Freeserve account as to obtain those defaults. |
The DUN settings that are important here are on the Server Types page of DUN Properties. It is reached:
open Dial-Up Networking highlight the Freeserve connectoid & go File | Properties click on Server Types page A tick in the box 'Log on to network' indicates:
Something to experiment with is to put a tick into Enable Software Compression; this has speeded up downloads for some people with some files. True hardware (i.e. not soft) modems implement compression in silicon - this is the LAP-M, MNP & V42Bis standards - so ticking this option should not make a difference. However, it has helped some & you may wish to experiment. |
|
| Check your house Having sorted out the computer & the modem as potential culprits attention now moves along the Line of Communication to the house. One first check - is the power supply to the computer earthed? Non-earthed power supplies have been reported to halve modem connection speed.
|
|
How long is yours? Shorten the modem line-cable. Many people have a line extension from the phone socket to the modem which is many metres long, and this modem line is responsible for far more speed loss than most people realise. Indeed, someone reported a 10,000 bit/s increase in speed just by replacing the modem cable for one from another manufacturer, yet of the same length. The ideal is to have as short a length of phone cable between the telephone exchange and the modem as possible and, whilst this does lead to visions of plugging the modem into a socket positioned on the outside of the exchange, there are many practical steps which everyone can take inside of their own house to shorten their internal high-loss lines. If you are contemplating replacing your own modem line-cable do remember that there is no such thing as a standard modem cable, and that you will need to obtain the correct replacement - take the old one along for comparison. Indeed, one computer manufacturer recently supplied cables which caused every telephone in the house to 'screech' on connection. |
|
|
And how many of them? Detach every other device. Whilst a telephone in every room may seem convenient it will eventually cause problems. This is usually considered in terms of Ring Equivalence Number [REN] & means that if you have too many devices on the telephone line one or more of them will not ring if someone phones you, but it also impacts the connection speed that the modem can establish. The issue here is one of the 'gain' on the line, & it is mentioned above and below. Each device will suck some of the juice from the line & may not leave enough for the modem. Testing this out is easy enough - detach every device [be it telephone, fax, answering machine, or whatever] - and see if it makes a difference. If it does then re-attach them one-by-one to see which one(s) make a big difference. |
|
|
And are they unusual? Various devices can get attached to the telephone line by various authorities. The effect of most of them seems to be to reduce the modem connection speed. Get a cable line... It is an odd situation. As mentioned above, the same twisted-pair wire on an internal network will allow 10 million bit/s, American experience with digital subscriber line technology has shown the existing infrastructure to be capable of 1.5 million bit/s or more, and even BT will drive it at 64,000 bit/s, yet when 2 lines are multiplexed (DACS boxes - see right) it becomes capable of no more than 14,400 bit/s. It has to be said that those in the UK with the best connection speeds usually seem to be on cable lines. 'Nuff said. ..for data connection. A [British] Telewest customer discovered that the box in the street had the line to each customer designated as either a voice or data customer. Persuading the engineer to switch his line to data doubled his connection speeds.
|
|
|
And is it corroded? Try the quiet line test. The Bible tells us that the moth and rust doth corrupt, and this most certainly is true at the telephone junction box. Typical signs are a noisy line. BT maintains an automated quiet line test (amongst other facilities) at 17070. My own experience with BT from many years back indicates that their twisted-pair line is actually a twisted-threesome of which only 2 lines are used. The engineers can switch this at the exchange without physical intervention and possibly bypass a poor connection on the third wire (worked for me)*. Other points are unshielded wires passing close to electrical motors/machinery introducing interference/hum onto the line. The biggest culprit here, of course, is probably the computer. Line cards within the local or main exchange are also capable of generating noise. *thanks to Peter Hurst - ex-BT - for pointing out that my information was nonsense! He explains that all underground wires are twisted-pairs, and that BT was probably using ‘split legs’ - “..the engineer will use a faulty pair and find one good wire in that pair to swap with yours”. |
|
Or too thin? Pump up the volume. The final aspect in being able to affect the speed of connection concerns the 'Gain' on the line (see also here & here). This means, quite simply, is the line too faint or too loud? To use, once again, BT as the example, it normally subjects the line to Automatic Gain Control (AGC). This usually works well for a voice call but is not necessarily most effective for modem communication as the modem usually contains AGC within it's own codec, & the two can conflict. Many users have reported dramatic speed improvements after asking for the gain to be increased/decreased. Just in case you are now confused by the fact that the gain may need to be put up or down, it is quite simple. 'Gain' talks of how much voltage the Telco is using to drive the telephone signal down the line. They do not want to melt the cables so the voltage is quite low, but a voltage it is nonetheless. If your house is close to the exchange this voltage can be quite low, whereas if far from the exchange it will need to be much higher. Also, across time corrosion at the various junctions will increase the resistance on the line & the voltage will need to be a little higher.
|
|
|
Or out of your control? There is one more item that impacts dramatically on connection speed - but there is nothing that you can do about it - and this is the signal-to-noise power ratio (SNR) on the entire line. Now, this is a topic for real Techno-Sluts & take the box at right under advisement as I'm a little rusty on these matters. |
|
||||||||||||
|
Modems make a much more intimate examination of the line than you might expect when they connect, & line quality is only one of the factors. Some modems also are able to give a report following connection which includes line quality: Use HyperTerminal to connect to your favourite ISP. At the point where the modem is still connected on the line to the ISP server it can report on many things to do with the connection. The command strings vary modem-to-modem: |
|||||||||||||
|
|||||||||||||
| Don't forget to enter ath0 to hang up | |||||||||||||
| NETCOM x2 Line Tester Netcom [in the UK] used to run a very nifty line-tester that produced multiple results, and amongst which was the SNR [shown below in dark blue] plus a graphical display of the line frequency-response. If the line can support x2 it can also support V.90. Unfortunately, sometime before 21 May 99 it stopped working (thanks to JohnFHH for reporting this) - the modem connects but nothing further happens, & this situation remains the same as at 8 Feb 00. This is a damn shame, as there is no better test for a modem. Zoltrix maintains a Phone Line Test (details here), but unless Netcom change their mind, what follows is purely a history lesson. Use HyperTerminal & enter the lines as shown below. The connection is standard V34bis, so don't get the collywobbles at what appears to be a slow connection. A sample from my own modem follows (the colour graphical output is much prettier, by the way, but shown here in text for speed of display).
|
|
+++ate1 OK atdt0845 079 8022 CONNECT 31200/LAPM Connected to ARCHOST v1.05 03-04-99 05:39:00 Caller number: 13380 Do you want ANSI/PC color graphics? (Y/N) >N Please wait, testing in progress... +-----------------------------------------------------------------------+ | This connection will support x2! | +-----------------------------------------------------------------------+ Press any key to continue... +-----------------------+-----------------+-----------------------------+ | x2-STATS Version 1.01 | 03-04-99 05:39 | Caller 13380 | +-----------------------+-----------+-----+-----------------------------+ | Elapsed Time 00:00:12 | Modulation V.34+ | | Blocks Received 1 | Speed 31200/31200 | | Blers 0 | Symbol Rate 3200/3200 | | Blocks sent 22 | Carrier Frequency 1829/1829 | | Link Naks 0 | Trellis Code 64S-4D/16S-4D | | Blocks resent 0 | Nonlinear Encoding ON/ON | | Link Timeouts 0 | Precoding OFF/ON | | Chars sent 0 | Shaping ON/ON | | Octets sent 158 | Preemphasis 6/0 | | Chars lost 0 | Rx Lev/TX Lev/SNR 20.0/18.2/44.2 | | Chars Received 0 | Echo Loss Near Far | | Octets Received 1 | Roundtrip Delay 18 | | Protocol LAPM | Retrains Request/Grant 0/0 | | Block Size 128 | Fallback Enabled | | Window Size 15 | HST Line Reversals 0 | | Compression NONE | HST Equalization Long | | Dictionary Size | SV: 07/26/96 DSP: 06/14/96 | | String Length | Reason: Online | +-----------------------------------+-----------------------------------+ Press any key to continue... +---------------------------------------------------------------+ | -18 | . x x . . . . . . . . . . . . . . . . . . . . . . | 0 | | -20 | . X X X X x . . . . . . . . . . . . . . . . . . . | 2 | | -22 | . X X X X X X X x . . . . . . . . . . . . . . . . | 4 | | -24 | X X X X X X X X X X X x x . . . . . . . . . . . . | 6 | | -26 | X X X X X X X X X X X X X X X x x x . . . . . . . | 8 | | -28 | X X X X X X X X X X X X X X X X X X X x . . . . . | 10 | | -30 | X X X X X X X X X X X X X X X X X X X X X . . . . | 12 | | -32 | X X X X X X X X X X X X X X X X X X X X X X . . . | 14 | | -34 | X X X X X X X X X X X X X X X X X X X X X X x . . | 16 | | -36 | X X X X X X X X X X X X X X X X X X X X X X X . . | 18 | | -38 | X X X X X X X X X X X X X X X X X X X X X X X x . | 20 | | -40 | X X X X X X X X X X X X X X X X X X X X X X X X . | 22 | | -42 | X X X X X X X X X X X X X X X X X X X X X X X X . | 24 | | -44 |=X=X=X=X=X=X=X=X=X=X=X=X=X=X=X=X=X=X=X=X=X=X=X=X=x=| 26 | |Level+---------------------------------------------------+Atten| | 0 0 0 0 0 0 1 1 1 1 1 1 1 2 2 2 2 2 2 3 3 3 3 3 3 | | 1 3 4 6 7 9 0 2 3 5 6 8 9 1 2 4 5 7 8 0 1 3 4 6 7 | | 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 | | 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 | +---------------------------------------------------------------+ Press any key to continue... Thank you for using the NETCOM x2 Line Tester. We hope you found what you were looking for! The NETCOM Operations Team Press any key to continue... Caller number: 13380 Thank you for calling. Disconnecting now. NO CARRIER +++ath0 OK |
|
| My Motorola soft modem regularly achieves 49,333 bit/s on this (very poor) line. |
Modem Speed Test Pages & other help:
| Modem Speed Test Page. Uses Java to objectively test the modem speed. Very useful. | |
![]() |
Modem Speed Test Pages at Toast Net. Four locations in USA to objectively test the modem speed on both text & graphics d/l. Mine was good on text, poor on graphics. |
| Bandwidth Speed Test Page at MSN. My lowly little Motorola scored brilliantly! If you have problems with the main link, goto the bandwidth page & click on the 'Bandwidth Speed Test' link. Thanks to Michelle for this link. | |
| Optimizing Internet Connections. This is a page for Gaming fanatics [there's redundancy for you] & therefore concentrates on good ping values. An excellent listing of Windows 95 update files. | |
| Modem Tweaking by Tweak3D. This is on a site for Gaming enthusiasts & concentrates on increasing the speed & stability of the modem. In part it discusses using iSpeed from High Mountain Software. | |
| lagless.com | Primarily aimed at anyone who plays online games with a modem |