Introduction
To connect 100 users located at three geographically dispersed sites we need a Wide Area Network or WAN. A WAN mainly functions at the Physical Layer, Data Link Layer, and Network Layer of the OSI model. In this network, we have used point-to-point links instead of switched circuits or packet switching since a carrier WAN T1 connection will only provide a point-to-point link between two ends. As a result, only a single communication path will be provided between users and remote networks for the communication of data. To build WANs several devices and communication media are necessary. We need switches, modems, routers, repeaters, CSU/DSU, and access servers, and transmission coaxial cable and fiber optics. Our maximum target connection speed is T1.
Main body
The 100 users at each of the sites are themselves interconnected through Local Area Network or LAN. A local loop is used that connects the users at one end to their Internet Service Provider or ISP. They have fixed bandwidth and in this case, we are using T1, which gives at the most 1.536 Mbps. As physical transmission media, we have to use both coaxial cable, for connecting the internal networks, and fiber optics. The network that has been built is permanent and dedicated with fixed bandwidth and unless the ISP changes its path, data between the two remote ends will always flow through the same carrier line and path.
The WAN network consists of a WAN switch, which is an internetworking device with multiple ports used for switching traffic. The routers at the ends of our WAN are connected by these WAN switches. We have also used an Access Server, which is a point that concentrates the dial-out and dial-in connections into our WAN. It is typically placed between the WAN and the various user computers. Next, we use a modem, which is an instrument for interpreting the various analog and digital signals being sent and enables the transmission of data over the physical media. At one of the user’s ends, modems are used for converting digital signals to analog ones, and at the destination end, the opposite is performed. Thus, a modem sits between a user and the WAN and works through the WAN. (Cisco Systems Inc, 2003)
Next, we use a channel service unit/digital service unit or CSU/DSU, which is a device that connects the router to our digital circuit, i.e. the T1. It is placed between the WAN switch and the end terminal. The CSU/DSU provides the users signal timing required for the communication among these various devices. The next device, which we have used, is a router, which sends the user’s message over the WAN created, to its destination point. A CSU/DSU is used for interfacing the router with a T1 here.
As for the internal LAN connection, we can use either a switch or hub, but since a switch boosts the performance of our LAN, we have used it here. Finally, we need computer systems for all of our end-users, which is 300, 100 each at the dispersed sites. They serve as both the server and the client. A subnet mask needs to be created matching the WAN interface of our routers. Once all of these are in order we can start communication among the users placed geographically apart.
References
Cisco Systems Inc; 2003; Cisco Networking Academy Program; Cisco Systems, Inc, Inc Cisco Systems, Cisco Networking Academy Program, Cisco Networking Academy Program, Networking Academy Program Cisco, Cisco Systems Inc.; Ed: 3, revised; Pearson Education.