Sunrise Consultancy is a medium-sized consulting firm that operates 17 offices a

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A WAN is wide area network which can be extended to for much greater distances and can even be international. It is also possible to link data networks together to form a network of networks. Some of these are world wide scope. The largest and most famous of these is the internet. There are three basic ways of organizing the lines. Dedicated, leased lines can be used, or lines can be shared by using either circuit switching or packet switching.

Leased lines: This is the simplest system for lines to be leased from telephone companies on a monthly basis. In most areas these lines are digital throughout, so it is not necessary to use modems. Leased lines are available with data rates from 56 kb/sec . Leased lines are most suitable when data must be transferred between two centers on a continous basis.

Circuit Switching: This method is actually very similar to placing a call on the ordinary switched telephone network. The connection is made only when a station has data to transmit. WAN circuit switching usually uses digital lines, making modems unnecessary and can operate at much higher data rates than an ordinary dial-up line with a modem. The integrated services digital network (ISDN) system is very well suited for use with circuit switched data. The basic ISDN interface uses two 64kb/sec channels plus a 16 kb/sec channel for network signaling. The two 64 kb/sec channels can be combined to give a data rate of 128 Kb/sec.

Packet switching: Each packet begins with a header that includes the address of the node to which the packet is being sent. Telephone companies and other service providers , operate packet switched networks. Each station of a WAN has an address and packets of data can be addressed to it from any other station. The network automatically chooses the best route which is not necessarily the shortest distance between the two nodes if the shortest route is busy a packet may be sent by a longer route. Each switching station in the network stores the packet briefly before sending it on to the next.

Here in this case the company operates from 17 offices around the world they have been using internet connections to exchange email and files. As the places from which the company is operating are not continous that is they are not connected lands which are separated by large distances. For this purpose a Packet switching WAN technology is best suited. As running leased lines to several locations would be very expensive and circuit switching has to be redone every time a message must be sent to a different destination. In contrast a packet network can send an individual message to any station or combination of stations with a simple change in the address on the packet. The speed is greater than 128 kb/sec.

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