Wide Area Network Transmission

With components such as bridges, routers and communications service providers, local area networks can be connected to create WANs. Communications services make use of the following three types of transmission technologies:

• Analog
• Digital
• Packet-switching

Analog Connectivity

Analog transmission refers to telephone lines used with modems. These can be:

• Dial-Up Lines - used for infrequent data transmissions.
• Dedicated Lines - used for frequent and continuous data transmissions. This method provides a ready communication link.

Digital Connectivity

Digital lines provide faster and a more secure transmission as compared to the telephone lines. Digital transmission does not require the use of modems. Following are the different forms of digital lines:

• DDS (Digital Data Service)
• T1
• T3
• T4
• Switched 56

DDS sends data through a device called a Channel Service Unit/Data Service Unit (CSU/DSU). This device converts digital signals into a form that is part of the synchronous communications.

Note: With synchronous communication, bits are sent in a timed, controlled fashion. Transmission stops at the end of one frame and starts again with a new one.

T1 and T3 use point-to-point transmission that can transmit voice, data and video signals. T1 offers high data speeds and is the most widely used type of digital line. T3 is the highest capacity leased line service available.

Switched 56 is a digital dial-up service that requires a CSU/DSU to be installed with each computer on the network.

Packet-switching Networks

Packet-switching is a fast and efficient way to transmit data over wide areas. With packet-switching, data is divided into packets of small size and a destination address is attached to each packet. This way each packet can be sent separately over the network. Packets are transmitted along the best route available between the source and the destination.