ISDN

In some areas, the only “high-speed” service offered will be ISDN (Integrated Services Digital Network). ISDN is an access technology that uses digital transmission with a bandwidth of up to 128 Kbps over your local telephone company’s ordinary copper wire lines. However, unlike your local telephone service, which transmits analog signals, ISDN can, over these same wires, transmit multiple digital signals simultaneously. There are two ISDN user interface standards: Basic Rate Interface (BRI) and Primary Rate Interface (PRI).

  • ISDN BRI is defined as consisting of two 64 Kbps B-channels and one low-speed 16 Kbps D-channel (used only for signaling).
  • ISDN PRI standards vary according to the geographic region the service serves. In the U.S. and Japan, ISDN services based on the PRI interface are defined as 23 B-channels plus a D-channel (all operating at 64 Kbps), yielding a total of 1.536 Mbps). In Europe, however, ISDN PRI is defined as 30 B-channels and one D-channel yielding a total of 1.984 Mbps.

Wherever situated, the slower D channel is always the last channel, (e.g. channel 24 in the U.S. and channel 31 in Europe), and it serves the purpose of call signaling, call setup, requesting network services, and routing of data over B-channels.

A terminal adapter (TA) is the piece of equipment you install at the end of an ISDN line in your home or business -– it can be an ISDN phone, a fax machine, or an ISDN “modem.”

There are two kinds of ISDN TAs, internal and external. TAs can look like modems, like computer bus cards, or like interface cards for PBXs or routers. Many ISDN phones and modems have analog jacks on the back that allow you to connect ordinary phones, fax machines, and other analog, non-ISDN devices.

External ISDN TAs are easier to install (they plug into your PC’s serial or USB port) but won’t give you maximum performance. Some, such as the Motorola Bitsurfr Pro or the 3COM Courier, actually look like modems and are often called “ISDN modems.”

The problem with ISDN is that it’s not scalable — you get 128 Kbps (a little over twice the speed of a 56k modem) and that’s it. Data is routed from your ISDN modem to your web host/ISP over the same copper wiring that you may have previously used for ordinary analog phone service, then out to the Internet.

ISDN is available from the local telephone company in most areas in the United States and Europe for around $150 for installation, $300 for the external adapter/modem, and a $50 to $100 monthly line fee. But use ISDN only if there isn’t another, faster option available, e.g. DSL.

T-1/E-1

A T-1 (E-1 in Europe) line’s data-carrying capacity is 1.5 Mbps (E-1 offers 2.048 Mbps) within 24 channels (E-1 offers 31 available channels), each channel having a 64 Kbps data transfer capacity. For most small businesses a full T-1/E-1 line may be overkill since such service is expensive. However, a fractional T-1/E-1 line or burstable T-1/E-1 may suit even a small website’s budget.

A fractional T-1/E-1 is a T-1/E-1 line that is channelized or partitioned, and is referred to as a “fractional configuration.” If a business does not need a full T-1/E-1 line it can lease any portion of the 24/31 64 Kbps channels, with the transmission method and rate of transfer remaining the same. This service is most preferable for a website that expects its traffic to be higher than 1 Mbps 50% of the time.

A burstable T-1/E-1 is a cost-effective Internet access solution for websites to receive direct, reliable, high-speed Internet connectivity. You only pay for the bandwidth that is used rather than for the total size of the circuit and bandwidth, much of which is often unused.

Access to the Internet is set at a minimum of 128 Kbps with burstability to the full T-1/E-1 capacity of 1.5/2.048 Mbps when necessary. Although a monthly minimum is based on sustained usage of 128 Kbps, burstable T-1/E-1 service always provides the availability of the full T-1/E-1 bandwidth. An unshared, point-to-point, full T-1/E-1 line can cost anywhere from $800 to $1500 per month, but a burstable or fractional T-1/E-1 is less — how much less will be based on the service you need.

For example, here’s how the cost for a burstable T-1/E-l might be calculated: Usage is usually monitored every day with SNMP (a network monitoring and control protocol) to create an end-of-month usage report. Rates are then averaged based on the mid-dle 90% of reported usage for the monthly basis. Reports should be included in your monthly billing.

Any T-1/E-1 installation (including burstable and fractional service) will come with a set-up fee of approximately $5000 that includes:

  • All the local telephone company loop charges and carrier fees.
  • Full 1.54/2.048 Mbps availability.
  • Cisco router or other certified network equipment.
  • T-1/E-1 CSU/DSU.
  • All T-1/E-1 installation charges.
  • T-1/E-1 set-up fees.
  • As many IP addresses as can be justified.


The Complete E-Commerce Book. Design, Build & Maintain a Successful Web-based Business
The Complete E-Commerce Book, Second Edition: Design, Build & Maintain a Successful Web-based Business
ISBN: B001KVZJWC
EAN: N/A
Year: 2004
Pages: 159

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