Certification: Cisco CCNA Routing and Switching - Cisco Certified Network Associate Routing and Switching
A WAN is referred to as a Wide Area Network. The basic purpose of a WAN is to provide a wide network on which people from distant and remote areas can communicate with each other. A WAN is formed when a number of MANs and LANs and interconnected to form a wide network. There are a number of components which are involved in WAN. These components include devices, protocols, connections etc. All of these components are collectively referred to as WAN Technologies. All of these components operate on the first three layers of the OSI Model; Physical layer, data link layer and Network layer.
It is important to have an understanding of each component in WAN technologies so that one can operate and manage the network. In fact, the process of troubleshooting demands in-depth knowledge regarding these components. In addition to this, you should also know how these devices, protocols and connections are interconnected with each other to provide you a perfect WAN. Following are the basic WAN technologies which you should be familiar with.
Point-to-Point links are used to establish a connection between the user and the remote location where he wishes to send the data. In this process, a link is established between the user and a carrier company, which then in-turn establishes a link with the remote network on WAN. These remote links make use of certain reserved protocols which carry out the purpose of transmission of data. In addition to this, the transmission is done is two ways; Datagram transmission and Data-Stream transmissions. This Point-to-Point link is one of the most essential processes in the establishment of a connection in a WAN.
In this process, the data is transmitted and the connection is established by using a dedicated physical circuit. One important aspect to note is that this connection is established and maintained by a carrier network in between. In this process, datagram transmissions and data-stream transmissions both take place. One example in this regard is ISDN.
In this process, data packets are transmitted by using a point-to-point link between the source and the destination through a carrier network. Statistical Multiplexing is also used in this case to allow multiple devices to connect to the network at once. Some of the examples in this regard include ATM and SDMS.
Virtual Circuits for WAN
Virtual circuits are non-physical circuits which are used for the purpose of establishing a connection over a WAN. These virtual circuits eliminate the need for physical circuits, hence saving a lot of costs and increasing the range of networks. There are basically two types of virtual networks, SVCs (Switched Virtual Circuits) and PVCs (Permanent Virtual Circuits).
Switched Virtual Networks (SVCs) are used to temporary networks which are created when they are needed and are terminated afterwards. This enables them to increase the overall bandwidth as well as decrease the costs as the networks are terminated when they are not needed. SVCs make use of three different phases. In the first phase the circuit is established, in the second phase the data is transferred and in the last phase the circuit is terminated.
Permanent Virtual Networks (PVCs) are permanent networks which are used in situations where the data has to be transferred continuously. It only used on phase, which involves the transfer of data. However, due to the continuously operating network, the bandwidth is reduced and the costs associated with the network increase.
WAN Dialup Services
WAN networks make use of dialup services which provide an effective way of communication over WANs. There are basically two types of Dialup services used in this regard; DDR (Dial-on-demand Routing) and Dial backup.
DDR is a service which creates and terminates a circuit automatically according to the requirement. In this case, a router is configured in such a way that it only receives certain amount of traffic. This means that the circuit is set to be activated when that particular traffic comes to the router and afterwards it is terminated. In this case, if the circuit is closed and some other traffic comes to the router which it is not configured to receive, the router will drop the data.
Dial Backup service is the one which provides backup in case the primary network fails. It automatically turns on when the primary network has got some issue or problem. This ensures that the network runs continuously without any break.
There are a number of devices which are used in the formation of a WAN. However, some of them are quite essential and require a good amount of consideration. Following are some of the most important devices used in a WAN.
Switch: WAN Switches are those devices which are used during the layer two, Data link layer, of the OSI model. It is generally used in carrier networks to allow the process of communication on layer two. WAN Switches basically perform the task of receive and forwarding frames to other devices.
Access Server:An access server is the device which manages the entire dial in connections. In fact, all of these connections are concentrated on this device. The access server then forwards these connections to the WAN. This means that it also provides dial out connections into a WAN.
Modem:A modem is a device which converts the signals in an appropriate form to be sent over the network. When the signals are to be sent over the communication line, the signals are converted from digital to analogue form by the modem. Similarly, when the signals are supposed to be received by a device, they are converted from the analogue to digital form by the modem. This ensures that the data is in the appropriate form at each point.
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