Surfing the ISDN waveDo you require higher bandwidth at home or office than your modem can handle?

Surfing the ISDN wave

Do you require higher bandwidth at home or office than your modem can handle? Well, ever considered getting an ISDN connection? With speeds beginning at 64 kbps, it is many times faster than an analog modem.

Payal Dhar

10/22/99

The ABC of ISDN
Integrated Services Digital Network is really the 'next step' to the analog modem connection to the Internet. Though ISDN uses the same twisted pair copper cables of the telephone lines, it transmits digital signals instead of the usual analog ones. Obviously, it requires the telephone company to be equipped with the necessary switches to allow the transmission of such data.

Whereas analog data consists of a continuous, complex signal, a digital signal comprises disparate bits making the transmission of digital data very fast. In a normal modem connection, digitization takes place at the modem level and the data is transmitted as an analog signal along the telephone line. In case of ISDN, an end to end digital pathway is provided so that the connection is made faster.

What makes it tick?
There are different kinds of ISDN connections, the most common one being Basic Rate Interference (BRI). BRI ISDN divides the telephone line into three parts, all of which can be used at the same time. These are:

1. Two Bearer (B) channels: which transmit data at a rate of 64 kbps (or 56 kbps, depending upon the telephone service available). The B channels can be used simultaneously or they can be bonded for a 128 kbps access---at an extra cost of course.

2. One Data (D) channel: which is the 'administrator' of the system. It takes care of call connection, disconnection, error correction, etc.

For users who require fast access to the Internet and also need a range of different services, the ISDN is an alternative. It is possible to connect up to eight different devices to a single ISDN line including ISDN fax machines and telephones. An ISDN line can be also be connected to a LAN using network bridges or routers letting all PCs on the LAN use the same line.

Getting things going
First, one needs to contact the telephone service provider and ask them to set up the ISDN line. Then an ISP has to be contacted to provide up the dial-up access, and finally the hardware has to be configured.

There are two types of terminal adapters, or ISDN modems as they are also called.
1. Internal adapters: These fit into a slot inside the computer. The slot must support the same type of bus as the terminal adapter. Internal adapters provide slightly better performance than external ones.
2. External adapters: These plug into a serial port outside the computer and, for obvious reasons, are easier to install and configure.

You will have to pay a one-time cost to set up the lines. Apart from that, you have to pay the ISP for Internet access, as well as the telephone company for use of the phone line. Admittedly, it not a cheap option of Net access.

The balance sheet

Pros
1. It provides a faster connection. While an analog modem has to dial, wait for an answer and then make the connection, an ISDN connection makes a call in almost an instant. An analog modem has to devote much to its energies to error correction; in an ISDN line the D channel takes care of such overheads and the throughput is much better.

2. It allows to connect multiple devices to a single line. It can also be connected to a LAN.

3. Downloads are about twice as fast and uploads about four times as fast.

4. It is a very versatile service, providing many diverse solutions.

Cons
1. It is difficult to set up and rather expensive.
2. Being a digital service, it is sensitive to outside interference.
3. Compared to Digital Subscriber Line or even Cable Modem technology, it is slow and expensive.

However, cable access to the Net and DSL are yet to catch up in India. For the time being it looks like we are stuck with ISDN for higher bandwidth at home and office.

In India, most of the major service providers---such as VSNL, MTNL and Mantra---have dial-up ISDN to offer, with Satyam likely to launch the service soon.

ISDN rates in India

For the ISDN telephone line
Registration Deposit: Rs. 3000/-
Initial Deposit: Rs. 9,000/-
Wiring charges up to Network Termination 1 for Basic Rate Access ( one-time charge): Rs. 600/-
Subscriber Interface Bus (one-time charge): Rs. 500/-
Monthly rental: Rs.1000/-

For Internet access (via an ISP)
VSNL
Hours Price(64 kbps) Price(128 kbps) Valid for
100 Rs. 5,500/- Rs. 11,000/- 1 year
250 Rs. 12,500/- Rs. 25,000/- 1 year
500 Rs. 19,000/- Rs. 38,000/- 1 year
One-time registration charges: Rs. 5,000/-

MTNL
Registration fee (one-time): Rs. 500/-
Hours Price(64 kbps) Price(128 kbps) Valid for
100 Rs. 4000/- Rs. 8000/- 1 year
250 Rs. 9000/- Rs. 18000/- 1 year
500 Rs. 14000/- Rs. 28000/- 1 year

Mantra Online
Hours Price(64 kbps) Valid for
500 Rs. 15,990/- 1 year
One-time registration charges: Rs. 500/-

Satyam Online
Dial-up ISDN services likely to be launched from November 1999.

The phone charges to DoT/MTNL
The usage charges for ISDN calls are same as for the analog modem
connection, subject to minimum charges of Rs 5000/- per month per
subscriber. This is in addition to the rental and the one-time installation
charges.

Why leased lines are being increasingly favored over ISDN?

While it is all very well to have an ISDN line as far as managing e-mail and surfing the Net is concerned, but if one has to maintain a web server or needs to be online continuously for some reason or other, it is a different story. An ISDN connection is 'on' only when it is being used. Keeping the line in use also means that the telephone costs are ticking away. It can be an expensive option and a leased line makes more sense if you require continuous access.

A leased line is a permanent link from the phone company to your local exchange and then to the ISP. It can provide dedicated access at various speeds, the most common ones being 64 and 128 kbps. Leased lines offer unlimited access at fixed charges, which could be a 2 to 3 lakhs (or more, depending on the connection) a year. Leased lines are available from most ISPs, including Mantra, MTNL, Satyam and VSNL. On the face of it, it seems very expensive, but if one is looking at continuous access, it ends up being more economical.

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