Transmission Options or WAN Services

There are a number of transmission options available today. They fall either into the analog or digital category. Next let’s take a brief look at each of these transmission types.

POTS Using Modem Dialup

Analog modems using basic telephone service are asynchronous transmission-based, and have the following benefits:

- Available everywhere
- Easy to set up
- Dial anywhere on demand
- The lowest cost alternative of any wide-area service

Integrated Services Digital Network (ISDN)

ISDN is a digital service that can use asynchronous or, more commonly, synchronous transmission. ISDN can transmit data, voice, and video over existing copper phone lines. Instead of leasing a dedicated line for high-speed digital transmission, ISDN offers the option of dialup connectivity—incurring charges only when the line is active.
ISDN provides a high-bandwidth, cost-effective solution for companies requiring light or sporadic high-speed access to either a central or branch office.
ISDN can transmit data, voice, and video over existing copper phone lines.
Instead of leasing a dedicated line for high-speed digital transmission, ISDN offers the option of dialup connectivity —incurring charges only when the line is active.
Companies needing more permanent connections should evaluate leased-line connections.

- High bandwidth
- Up to 128 Kbps per basic rate interface
- Dial on demand
- Multiple channels
- Fast connection time
- Monthly rate plus cost-effective, usage-based billing
- Strictly digital

ISDN comes in two flavors, Basic Rate Interface (BRI) and Primary Rate Interface (PRI). BRI provides two “B” or bearer channels of 64 Kbps each and one additional signaling channel called the “D” or delta channel.
While it requires only one physical connection, ISDN provides two channels that remote telecommuters use to connect to the company network.
PRI provides up to 23 bearer channels of 64 Kbps each and one D channel for signaling. That’s 23 channels but with only one physical connection, which makes it an elegant solution- there’s no wiring mess (PRI service typically provides 30 bearer channels outside the U.S. and Canada).
You’ll want to use PRI at your central site if you plan to have many ISDN dial-in clients.