ZipLink Is ISDN-Ready Today

Choosing ISDN greatly increases your connection speed to the Internet for individuals and small and large companies. Don't leave your office unZipped!

The majority of ZipLink's POPs are ISDN ready. To view a complete list of ZipLink's access numbers for ISDN availability in your area, go to ZipLink's Internet Infrastructure page.

Microsoft's Get ISDN pages can help you work with your local telephone company for ISDN services. Plus, the site has lots of great background information on ISDN services and products. Every one of ZipLink's local access numbers is capable of handling ISDN connections. You just need to determine whether you can get ISDN service from your telco, then procure the proper hardware and you're ready to go.

Why ISDN?

ISDN stands for Integrated Services Digital Network and is a high-speed, fully digital telephone/telecommunications service that works over existing copper telephone wiring. Most of the world's existing telephone network is already digital. The only part that typically isn't digital is the section that runs from the local exchange to your house or office. ISDN completes that final leg of the digitized network. It can operate at speeds up to 128 kilobits/second, which is five or more times faster than today's analog modems.

How Do You Get Dial-Up ISDN?

Here are the steps involved in getting your ZipLink ISDN connection up and running:

Loop Qualification

The phone company engineers test your line and determine if ISDN service is available at your location. Because ISDN is a digital service, it is sensitive to outside interference. You must be within a given distance of the telephone company's equipment that serves you. To get this process started, call your phone company. After they determine if your area qualifies, they will provide you with rate information.

What is ISDN?

ISDN is an acronym for Integrated Services Digital Network. What this means is that many services (voice, video, facsimile production, file transfer, e-mail, games, etc) can be transmitted digitally, simultaneously, over one or many telephone lines at a much faster rate than with the standard analog method of data and voice transmission.

There are two types of ISDN lines available. The first is called a BRI or Basic Rate Interface. This type is often referred to as a 2B+D and is the type of line you are likely to come into contact with.

A BRI is composed of 2 B channels or Bearer channels and a control channel referred to as a D or Delta channel. Each Bearer channel carries a bandwidth of 64Kbps for a total possible bandwidth of 128Kbps when used together, more than four times the bandwidth of modems.

The D channel is used to carry session information, line status and general control information wich is transmitted unnoticed by the user. The D channel carries a bandwidth of 16Kbps in the case of a BRI.

The other type of ISDN line is a PRI, or Primary Rate Interface. It comprises 23 B channels and 1 D channel, and thus carries up to 23 concurrent calls, either voice or data,. PRI is how ZipLink brings customer calls to its POPs.

There are several types of Hardware necessary to impliment ISDN.

NT-1 (Network Terminator-1) - This is a very simple devices that provides a good majority of the flexibility of ISDN from a user perspective. An NT-1, simply put, is an arbitrating device. It receives a signal over the ISDN line and makes a decision as to which of several ports attached to the NT-1 the call is routed to, such as an analog telephone, fax or to a computer for a data call. The NT-1 is necessary in providing multiple services on one ISDN line. In the United States, the NT-1 is the responsibility of the user, and most ISDN devices that will be purchased in the US have an NT-1 in them.

Terminal Equipment - This is a general term for any ISDN equipment attached to an ISDN line. There are many flavors of terminal equipment, three will be discussed here that fall under one type, the terminal adapter.

Terminal Adapter (TA) - A piece of terminal equipment that transmits and receives digital signals enabling a piece of non-ISDN hardware, such as a computer, to be attached to an ISDN network. Most often this is attached to a computer via a serial cable, Ethernet card or the compter bus. In common usage, TA is directly analogous to modem and is often simply refered to as an ISDN modem.

Digital or ISDN modem - Although not a modem, this term best describes terminal equipment that operates in a single user environment and can be used like a modem from an end user perspective. Most often these connect to the computer via a serial port and are likely to respond to a standard Hayes AT command set. These are the devices that dial up customers are most likely to have. Examples include the Bitsurfer Pro, 3com Impact, USR Sportster ISDN, etc.

ISDN Bridge - An ISDN device which forwards traffic between network segments based on data link layer information. Thes segments would share a network layer address. This could be used to connect to separate offices so that they would exist on the same LAN.

ISDN Router - A device which forwards traffic between two networks. This is done on the network layer via routing tables constructed by routing protocols. ZipLink's ISDN business customers are likely to connect using these devices.

In addition to the Hardware, it is important to understand a few definitions associated with Terminal Equipment. These include:

SPID (Service Profile IDentifier) - This is a number programmed into the ISDN switch by the phone commpany identifying information about a physical ISDN line. This includes the Directory Numbers (DN) as well as services and features provided.

Directory Number (DN) - This is simply a seven digit phone number attached to a Bearer Channel. With a BRI, a user has two B channels, and thus possibly has two phone numbers associated with it.

Data Over Voice Bearer (DOVB) - This is the common name for sending ISDN data over a voice bearer channel which is advantageous in those areas that don't meter for voice services (most notably Nynex and SNET).

Additional Information:

3com setup  
Bitsurfer setup    
USR Sportster ISDN setup   

Win95 Serial TA setup   
Trouble Shooting guide  
Centrex ISDN services (Nynex)   

Additional Reading:

Glossary of ISDN Terms - Terms to be familiar with when you take the ISDN route.

ISDN Hardware Reviews - A thumbs up/thumbs down review of ISDN hardware.

Dan Kegel's ISDN Page - Anything you could possibly want to know about ISDN.

ISDN De-Mystified - A nice overview of ISDN in plain English.

How to Use ISDN for Business and Work-At-Home Applications - Answers to many questions regarding ISDN benefits and equipment choices.

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