Dial-up and dedicated leased lines can be connected to a telephone network by using line services based on different transmission technologies. The following table describes these transmission technologies.
Table 3.2 Description of Transmission Technologies
Technology | Description |
X.25 | X.25 is a set of protocols incorporated in a packet-switching network. An X.25 packet-switching network uses switches, circuits, and routes as available to provide the best routing and transmission of your data at any particular time. |
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Frame Relay | Frame Relay is a packet-switching technology that evolved from X.25. It performs much faster than X.25, due to reduced overhead. It requires a Frame Relay – capable router that can route and transfer data from your server to remote users. |
Asynchronous Transfer Mode (ATM) | ATM is also an advanced form of packet-switching. It is a broadband method that transfers data in 53-byte cells rather than variable-length frames. It produces uniform frames that network equipment can switch, route, and move more quickly than frames of different sizes. ATM can be used with any media that include the necessary physical interfaces. |
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ISDN – Basic Rate Interface (BRI) | ISDN-BRI employs digital transmission that divides its available bandwidth into two 64-Kbps B channels and one 16-Kbps D channel, using existing regular telephone lines. |
ISDN – Primary Rate Interface (PRI) | ISDN-PRI has a larger bandwidth capacity than ISDN-BRI. Primary Rate ISDN provides 23 64-Kbps B channels and one 64-Kbps D channel. |
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Fiber Distributed Data Interface (FDDI) | FDDI is a high-speed token-passing ring network that uses fiber-optic media and that was developed for high-end computers. It is used for environments that connect components such as mainframe and minicomputers in a traditional computer room, for backbone networks, for networks that require high data rates and fairly large bandwidth, and for high-speed office networks in general. |
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Synchronous optical network (SONET) | SONET is an emerging fiber-optic technology that can transfer data at more than one gigabit per second. Networks based on this technology are capable of delivering voice, data, and video. |
Table 3.2 Description of Transmission Technologies (Continued)
Technology | Description |
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Switched Multimegabit Digital Service (SMDS) | SMDS is a switching service provided by some local exchange telephone networks. SMDS uses the same fixed-length cell relay technology as ATM and provides high-speed communication for multicast programs (that is, programs transmitted from one point to many simultaneous remote users, such as video broadcasts). |
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T1 | T1 is an AT&T term for a digital carrier facility used to transmit a Digital Service 1 (DS-1) formatted digital signal at 1.544 megabits per second. |
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T3 | T3 is a digital carrier facility used to transmit a Digital Service 3 (DS-3) formatted digital signal at 44.746 megabits per second. |
The preceding table provides some information you can use to choose what technology best supports your Internet Information Server bandwidth requirements. In some cases, an enterprise might need to use a mix of available services. For example, the 1995 data communications WAN at Microsoft is a mix of services, primarily composed of point-to-point leased circuits of 64 - kilobit per second or higher bandwidths, with smaller sites using X.25 services, ISDN-BRI, or analog dial-up.
The following table compares a few of the transmission technologies, listing different technologies' connection options, send and receive speeds, and number of simultaneous connections.
Table 3.3 Comparison of Transmission Technologies
Transmission method | Continuous connection | Send speed | Receive speed | Readily available | Simultaneous users |
Analog modem | No | Up to 28.8 Kbps | Up to 28.8 Kbps | Yes | 1 – 10 |
ISDN | No | 128 Kbps | 128 Kbps | Yes | 10 – 500 |
T1 and fractional T1 | Yes | 1.5 Mbps | 1.5 Mbps | Yes | 50 – 500 |
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T3 | Yes | 24 – 43.5 Mbps | 24 – 43.5 Mbps | Yes | 5,000 + |