Types and Characteristics of WAN

Definition of WAN

WAN means Wide Area Network. It can be defined as a network that covers large geographical areas, and functions as a link connecting many Local Area Networks (LANs). It is also defined in practice as a network that passes through a commercial carrier by means of any of the numerous WAN technologies.


Major Components for a WAN

The major components for the smooth functioning of a WAN are modems, switches and routers.

CPE

A Subscriber to a WAN has some equipment on his premises called Customer Premises Equipment (CPE). CPEs are either owned by the subscriber or hired from the service provider. CPEs are connected to the nearest central office of the service provider with a copper cable. This cabling is referred to as the local loop or "last-mile".

DTE/DCE

Data are placed on the local loop by devices called Data Circuit-Terminating Equipment (DTE). The main function of the DCE is to provide a crossing point for the DTE into the communication link on the WAN cloud.



Wan Standards

WANs operate using layer 1 and layer 2 levels which are the data link layer and the physical layer. How to provide electrical, mechanical and functional connections to ISP services is defined by the physical layer protocols, while the data link layer determines how information is encapsulated for transmission to distant locations.

Encapsulation

The packaging of data in a particular protocol header is referred to as encapsulation. WANs operate at the physical layer and the data link layer of the OSI model. WAN encapsulation types supported by serial interfaces (Synchronous Data Link Control, Point-to-Point Protocol, Frame Delay, etc.) are manually specified. WAN encapsulation must be the same on both sides of the point-to- point link, irrespective of the type used.



Packet and Circuit Switching

Circuit-switching and Packet-switching are used in high-capacity connections to get data over the network.

General Routing Issues

The standard procedure that specifies how routers interact and transfer data on a network is known as routing protocol.

Protocol

Routing Information Protocol (RIP) is used by routers to steadily adjust changes to the network connections and transmit information about which network routers can be reached and the distance between them.




Circuit Switched Leased Lines

Before users on the network can communicate, a dedicated circuit between nodes and terminals must be established. This is the function of a Circuit Switched Network.

Terms related to a Circuit Switched Network

Frame Relay (FR) This is a telecommunication service designed for cost-efficient data transmission among LANs Basic Rate Interference (BRI) Small businesses use Basic Rate Interference service for Internet connectivity. Primary rate interface (PRI) PRI refers to the telecommunications standard for carrying voice and data transmissions between two locations.

Packet Switching

Protocols in which messages are broken up into tiny packets before transmission over the Internet are called Packet switching. These packets are reorganized into the original message at the destination.



Asynchronous Transfer Mode (ATM)

ATM refers to a cell relay (Packet switching network and protocol) which programs data into small fixed-sized cells. Packet Switched Data Network (PSDN) is a data communication network. Instead of establishing a physical communication signal like the public telephone (Circuit Switched Network), a Packet Switched Networks sends packets on a fixed-length basis assigned with both source and destination addresses.

Mobile and Broadband Services

Bandwidth connections over copper wire telephone lines are brought to homes and small businesses through Digital Subscriber Line (DSL), if within the range of the telephone exchange. High bit-rate Digital Subscriber Line (HDSL), one of the first forms of DSL, is used for wideband digital transmission within a corporate site, and between the telephone company and a customer. Provision of equal bandwidth in both directions is the main feature of HDSL. A system that sends data at 128 Kbps on a normal copper telephone line from a user to a destination through digital transmission is called IDSL. Operators connect to consumers via copper local loops; then add their equipment to offer broadband and other services by accessing local exchange offices.

Benefits of using DSL

The benefits include instantaneous transmission of voice, data and video over ordinary copper phone lines, elimination of Internet information and graphic download delays, provision of a cost-effective high speed Internet connection for users, and online real time presence like a LAN connection. With an average broadband take up rate of over 70,000 per week during the three months leading to December 2005, the UK presently has more than 10 million broadband connections, against 9.792 million in December same year.