I used to work as a network/telecomms engineer within the Business Online Group in Brentford, Middlesex. During that time a large part of my working day was spent trying to solve problems customers encounter when dialling into the BOL service, over the last few months of my employment there my attention was centered on telecoms issues and their causes and solutions. Here are some of the things I came across during my research. Any queries, questions or things to add?, then mail me.
These problems fit into 2 categories...
Please Note :Not everyone will be affected by these problems and if you are getting a satisfactory speed with your ISP then I would recommend you leave it alone!!! Also note that different phone companies are affected by different problems. The following table is only a guide and should not be treated as a final decree of truth!
| Telco | WB900 | DACS | AGC | Number Unavailable | Call Gapping |
| BT | Yes | Yes | Yes | Yes | Yes |
| Kingston Communications | No | No | ? | Yes | ? |
| NTL | No | No | No | Yes | ? |
| Cable & Wireless | No | No | No | Yes | ? |
| Telewest | No | No | No | Yes | ? |
In the 1980's and early 90's BT would create new phone lines by taking an existing phone line and splitting it into two, thus creating a new one, using a system known as WB900. This gives lower quality phone lines but ones which still give the 14.4kbps speeds they are required to provide by law. This will obviously affect connection speeds, usual symptoms are connection speeds being limited to about 28.8kbps on a V90/K56Flex modem. Unfortunately there is nothing you can do about this without changing the phone line itself which is an expensive option. BT are no longer using this system to provide new phone lines but existing installations are not yet being replaced. Brief details of this system as described by BT themselves can be found in a report BT made to OFTEL, this is available on the Oftel website, the URL is:
http://www.oftel.gov.uk//NICC/Public/INTFR-I1.PDF
and again in this report:
http://www.oftel.gov.uk/competition/llu0500.htm
The simplest solution to this for most V90/K56Flex users is to disable the V90/K56Flex functions within their modem, thus forcing it to connect using the 33.6kbps protocols(V34, etc.). This should give a quicker dial up authentication to your ISP and will give a more stable/reliable connection once you are connected.
- Oftel has reorganised its site so this link is currently out of order!
DACS is one way of quickly providing phone service to a location which has run out of spare lines, only used if several preferable methods have failed. This system has replaced the aforementioned WB900 system.
In the exchange, an
"exchange unit" connects to two normal analogue lines. These two lines are then digitised and combined using standard ISDN technology (2B1Q line code, time division multiplexing for those in the know!) and sent down one pair of wires to the users. On the pole in the street near the users, a "remote unit" separates the lines back into two analogue lines. There is some clever circuitry to copy the ring cadence and hook status, and the line voltage is increased to around 100V so there is enough power to ring a REN of 4 on each line simultaneously.
As far as the exchange and the users are concerned, DACS is almost completely transparent - users are not aware of it. The exception is V.90/K56Flex modem users, who find their maximum connection speed is reduced to around 28.8k.
Brief details of this system as described by BT themselves can be found in a report BT made to OFTEL, this is available on the Oftel website, the URL is:
http://www.oftel.gov.uk//NICC/Public/INTFR-I1.PDF
and again in this report:
http://www.oftel.gov.uk/competition/llu0500.htm
The simplest solution to this for most V90/K56Flex users is to disable the V90/K56Flex functions within their modem, thus forcing it to connect using the 33.6kbps protocols(V34, etc.). This should give a quicker dial up authentication to your ISP and will give a more stable/reliable connection once you are connected.
- Oftel has reorganised its site so this link is currently out of order!
Update : The Sunday Times Culture Magazine ran a feature on the DACS system in its 6th August 200 issue, resulting in much public concern. See the responses here - This page has moved so sadly no link currently.
Update : The ASA(Advertising Standards Authority) penalised BT for one of its adverts which misled customers due to its lack of information regards the DACS system. Read it here.
Analogue phone lines have a gain setting, these are generally set automatically, however this auto setting can result in a reduced connection speed. If you constantly get low connection speeds you may improve things by asking your telecomms supplier(Usuall BT) to turn the Auto-gain control off. If this still gives no improvement you should then ask BT to increase the gain on the phone line.
The current explosion in 0800/0845 internet access has taken the UK telecomms companies by surprise. The current telephone network is not able to handle the number of calls being made to these types of numbers, as a result you will quite often hear a tone similar to the engaged tone when dialling into your ISP. This is often NOT due to a lack of capacity at your ISP but is a fault in the telephone network. Most commonly this occurs when your call has to change from the network of one phone company to another. For those of you that didn't already know there are several operators besides BT operating in the UK, companies such as...
Update: These excerpts came from a vnunet.com article dated Wed Aug 09 2000
The original is available here.
Unmetered boom could choke UK phone lines
The UK's telephone networks are not ready to cope with the surge of traffic that widespread availability of unmetered internet access would generate, according to the head of the UK's largest ISP.
Speaking at investment bank Robertson Stephens' International Investors Growth Conference in London this week, Freeserve chief executive John Pluthero said there is insufficient capacity in BT and cable operators' local exchanges, interconnect points and back-end systems to cope with a major shift to unmetered access.
"There's no way a significant proportion of the UK internet population could go on to unmetered tomorrow," said Pluthero. Unmetered access is already widely available, although many services restrict subscriber numbers and some have withdrawn services because they were not financially viable.
The market is set to change from next month when BT, under instruction from telecoms regulator Oftel, has to sell wholesale unmetered accounts to competitors - a scheme called Friaco (flat rate internet access call origination). Most ISPs plan to offer unmetered services for fixed fees using Friaco.
But with Friaco due to start next month, the phone networks need upgrading. "This is going to take many months to scale up," said Pluthero. He told delegates of Freeserve's experience when it launched the UK's first subscription free internet service in September 1998. "At one time, at a local exchange in Bristol, you had a one in six chance of getting a dial tone," he said.
Coupling the network shortfalls with the fact that Friaco pricing for ISPs is expected to fall sharply after its first review in December, customers could be waiting until next year before a real choice of reliable services becomes available. Bill Dixon, telecoms analyst at Robertson Stephens, said BT is still failing to provide what customers want, such as direct digital access and installation when they want. "It's bad for UK Ltd if you don't have a good telecoms infrastructure," he said.
Details of this system are scarce though what is known does not fill me with confidence in the phone system!
"If a local switch or exchange runs out of capacity in routing calls to a non-geographic number (i.e.: 0845) then the switch will "Call Gap" the service. This means that it will only allow 1 in n calls through and reject the others before they hit the switch. The rejected call can come back as an engaged tone, or as a network busy message. By the law of averages, if gapping is set to 4, then one attempt in 4 will get through. BT use Call Gapping as a method to protect their switches from overload. Call Gapping fluctuates dynamically with time. So, if you local exchange has lots of capacity then your are unlikely to be confronted with engaged-tones."
Another source informs me that the gapping level is not capacity of the switch but is set manually by the phone company engineers and that the practice can be applied to any number not just non-geographical ones. The system is designed to kill calls which are unlikely to succeed and thus clog the network.
Obviously there is nothing you as a user can do to avoid this.
Please Note :Not everyone will be affected by these problems and if you are getting a satisfactory speed with your ISP then I would recommend you leave it alone!!! Also note that different modems/chipsets are affected by different problems.
Every modem has a BIOS(Basic Input Output System). This bit of software handles all the data flow from the modem into the computer and from the modem to the phone line. The BIOS can be thought of as a translator which tells the modem what it can do and what its being asked to do. Most modern modems have a BIOS which can be upgraded, this process is known as "Flashing the BIOS". This allows a modem to be given a new set of languages/commands it can use/understand.
If you are having problems getting a connection or continually getting slow connections you may find that upgrading the BIOS on your modem helps. To find out if there is an updated BIOS for your modem have a look at the web page of the company who made your modem or contact the company who sold you the modem. For a list of modem manufacturers web pages see the more information section.
In a similar fashion to the BIOS every modem has a driver, this piece fo software is specific to your model of modem. The driver tells your operating system(Windows 95/98 at a guess!) how to talk to your modem in a way it can understand. There are a few generic drivers which will work with any modem with a particular chipset at its heart, however these generic drivers tend to give a less than impressive performance. Its best to use the correct and most up-to-date driver available for your modem. To find out if there is an updated driver for your modem have a look at the web page of the company who made your modem or contact the company who sold you the modem. For a list of modem manufacturers web pages see the more information section.
For a modem to transfer data down a phone line to a modem at your ISP the two modems must agree on a common langauge. One which they both understand and one which gives the highest possible data transfer rate while having the minimum of errors, this langauge is known as a protocol. Modern modems tend to have a maximum speed of 56kbps(Kilobits per second). There are however 2 main protocols which give this speed, these are V90 and K56Flex. To further complicate things there are also several versions of both of these protocols, many of which are incompatible with each other. Additonally, to gain a 56kbp connection relies on certain asumptions of the telephone system, namely that the phone line you use is a direct connection to your ISP with no analogue-digital conversions en route, unfortunately this is very rarely true due to systems such as DACS and WB900. As a result of this you will rarely get a connection higher than 50kbps, anything over 40kbps should be considered good from a 56kbps modem.
Many of you will own a PC which came with an internal modem pre-installed, nowadays this tends to mean you have what is known as a WinModem. These modems are not true modems, they rely on the parent PC for all of their processing and as such make your PC work harder than if you had a true hardware modem which does all its own work. WinModems are notorious for giving slow/unreliable connections. The only way of improving things is to ensure you have installed the latest BIOS and are using the latest drivers.
If you are about to buy a new modem you would be advised to buy a true hardware modem. Most external modems are hardware ones. USB ones are generally Winmodems. Any linux users reading this take note that many Winmodems will NOT work under Linux(Though take a look at LinModems and search for Google for the Rockwell winmodem driver for Linux).
Another Winmodem problem has recently come to my attention. This problem affects users with Windows 98, both versions, who have Lucent based Winmodems. There appears to be a bug in an application called RNA, which is a major part of the DUN system in Windows. If a Lucent Winmodem fails to connect on the first try to your ISP you may find that the RNA application will not exit correctly and will stop you from connecting to your ISP unless you kill the application using the task manager(use Ctrl-Alt-Del once to get this and then end the RNA-app entry in the list) or you reboot your machine. Mention of this appeared on the Microsoft Support web site but the link escapes me, I will add it here when I can find it!
IONet - A (Huge!) List of Modem Manufacturer Web Sites.- Link currently broken
Modem-Help - A Very Comprehensive Modem Troubleshooting Web Site.
DUN Error Codes - What do those Windows error codes mean? Find out here!.
Windrivers - Modem Identification Page(Also a good source of drivers).
V90.Com - Details Of the V90/K56Flex Protocols.
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