CSI-09 COMMUNICATION TECHNOLOGY

WIDE AREA NETWORK (WAN)

AUTHOR - V. V. SUBRAHMANYAM

COMPUTER NETWORK

Interconnected collection of autonomous computers.

KEY ELEMENTS OF A NETWORK

MEDIA: Provide pathways over which data can travel

NODES: Provide a means for inputting and outputting data over the transmission media

PROTOCOLS: Provide the common set of rules for managing the network pathways and the flow of the data.

TYPES OF NETWORKS

LOCAL AREA NETWORK (LAN) METROPOLITAN AREA NETWORK (MAN) WIDE ARE NETWORK (WAN)

LOCAL AREA NETWORK (LAN)

These are privately-owned networks within a single building or campus of up to a few kilometers in size. LAN’s are distinguished from other kinds of networks by 3 characteristics.

Size Transmission technology Topology

METROPOLITAN AREA NETWORK (MAN)

It is a bigger version of a LAN and normally uses similar technology. It might cover a group of nearby corporate offices or a city and might be either private or public.

A MAN can support both data and voice

WIDE AREA NETWORK (WAN)

Wide area network (WAN) is a data communications network that covers a relatively broad geographic area and often uses transmission facilities provided by common carriers, such as telephone companies.

SUBNET

Collection of communication lines and the routers form the subnet.

POINT-TO-POINT LINKS

This provides a single, pre-established WAN communications path from the user premises through a carrier network to a remote network.

CIRCUIT SWITCHING

It is WAN switching method in which a dedicated physical circuit is established, maintained and terminated through a carrier network for each communication session.

PACKET SWITCHING

It is a WAN switching method in which network devices share a single point-to-point link to transport packets from a source to a destination across a carrier network.

VIRTUAL CIRCUIT

It is a logical circuit created to ensure reliable communication between two network devices.

WAN VIRTUAL CIRCUITS

Two types of WAN virtual circuits exist:

Switched virtual circuits (SVC) Permanent virtual circuits (PVC)

SWITCHED VIRTUAL CIRCUIT

These are virtual circuits that are dynamically established on demand and terminated when transmission is complete.

PERMANENT VIRTUAL CIRCUIT

It is a permanently established virtual circuit

WAN SWITCH

It is a multiport internetworking device used in carrier networks.These devices typically switch such traffic as Frame Relay, X.25, and SMDS and operate at the data link layer of the OSI reference model.

ACCESS SERVER

It acts as a concentration point for dial-in and dial-out connections.

MODEM

It is a device that interprets digital and analog signals, enabling data to be transmitted over voice-grade telephone lines.

CSU/DSU

A channel service unit/digital service unit (CSU/DSU) is a digital interface device that adapts the physical interface on a data terminal equipment device to the interface of a data circuit terminating device in a switched-carrier network.

ISDN TERMINAL ADAPTER

It is a device used to connect ISDN basic rate interface (BRI) connections to other interfaces, such as EIA/TIA-232. It is essentially an ISDN modem.