ISDN : SDN pricing, ISDN loose traffic

ISDN
The most common type of circuit switching used in business today is an ISDN. “Integrated services” means that a user can send voice, data, and video across the network at the same time. “Digital” refers to the fact that the lines provided by the telephone company transmit digital, not analog, signals. Digital is cleaner and faster than analog. Computers using a normal analog phone line use modems to convert between the computer’s digital signal and the phone line’s analog capabilities. ISDN, being digital, requires no modem but does require the use of a network adapter. It looks just like an external modem but costs three times as much.

ISDN comes in two sizes: large and really large. Basic rate interface (BRI) is normally used by a single person, while dozens of employees may use one primary rate interface (PRI) connection for voice and data traffic. BRI is used for applications such as telecommuting, Internet access for a single user, and, occasionally, videoconferencing. PRI has the same bandwidth as a T-1 and is used for similar purposes: to connect multiple users to the Internet or to carry voice calls from a PBX to a carrier.

BRI
ISDN technicians say BRI is “2B + D,” meaning the service has two separate bearer channels for transmitting information and one data channel used behind the scenes for signaling. The bearer channels have 64-Kbps bandwidth each, and the data channel has 16-Kbps bandwidth.

PRI
PRI is “23B + D.” There are 23 bearer channels and 1 data signaling channel. These 24 channels are the standard used in the United States and in Japan. Elsewhere in the world, PRI ISDN uses 30 channels. One of the main advantages of the D channel used in PRI ISDN is that an inbound caller’s phone number can be passed along to the PBX, which is very helpful for call centers.

ISDN pricing
ISDN installation costs vary widely from carrier to carrier and can sometimes be waived. After the customer has purchased the equipment and paid for the installation, the following monthly recurring charges apply with both types of ISDN: line charges, local calls (if measured service), and longdistance toll calling.

Monthly line charges for BRI ISDN are between $50 and $150. PRI ISDN line charges are normally between $300 and $1,000. The charges for local calling and long-distance calling are about the same as standard voice telephone call rates.

ISDN began to be widely offered by the telephone companies in the late 1980s. Although the service promised many improvements over previous technologies, customers were not eager to subscribe. Some blamed poor marketing by the telephone companies, but the real reason is probably because the initial service offerings were too confusing to business people. The phone companies required prospective ISDN customers to be too involved in minor technical decisions. The whole process was a turnoff to business people, and ISDN got a bad name. Some said ISDN really stood for “innovations subscribers don’t need.” Over the past few years, the telephone companies have made new activations less painful, and the demand for fast connections to the Internet has breathed new life into ISDN service.

ISDN loose traffic
ISDN is a measured service, and users pay for each minute of calling in addition to a flat monthly fee. If a new ISDN customer does not inform the long distance carrier of the new ISDN line, then the calls will be billed on the LEC’s ISDN bill. The calls will be billed at casual rates, which may be $0.35 to $3 per minute. Customers whose ISDN calls are being billed at casual rates on their LEC bill should inform their long-distance carrier, which can move the ISDN loose traffic to the long-distance bill. This should result in much lower pricing.

Although circuit switching was an improvement over dedicated private lines, phone company upper management still was not satisfied and continued to worry about traffic jams on their telephone network. The biggest problem with circuit switching, from a telephone company perspective, is that, similar to regular voice calls, the phone company circuit is tied up for the entire length of the phone call. During a regular voice call, if one person sets the phone down to check the roast in the oven or answer the doorbell, the phone line is still tied up. Even though the line is quiet and no data is being passed across it, the line is still tied up and no one else can use it.

When thousands of businesses across the country make simultaneous circuit switching calls, there may eventually be a shortage of capacity. Once again, phone companies sent their engineers back to the drawing board with a similar charge “to figure out a way to send even more data across the existing phone network.” The end result was packet switching.