Evolution of Wan Essay

BACKGROUND ON WAN WAN, or Wide Area Network, is a computer network that covers a broad area (i. e. any network whose communications links cross metropolitan, regional, or national boundaries. The first “wide area network” was created in 1965 when the inadequacy of the telephone network for running programs and transferring data was revealed. As an experiment, computers in Berkeley and MIT were linked over a low-speed dial-up telephone line to create the first wide area network. NASA, NSF, and DOE became heavily involved in Internet research and all three of these branches developed the first wide area network based on TCP/IP in the mid 1980s.

There are 4 Types of Wide Area Network connections; leased line connections, circuit switching connection, packet switching connection, and cell relay connection. 1. Leased line connection: A premium internet connectivity product, delivered over fiber normally, which is dedicated and provides un-contented, symmetrical speeds. An advantage of having a lease line connection is that it is the most secure connection. However, the disadvantage of the leased line is that it can be very expensive. 2. Circuit switching connection: A network that establishes a circuit between nodes and terminal before the user may communicate.

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The bit delay is constant during a connection because each circuit cannot be used by other callers until the circuit is released. An advantage of having a circuit switch connection is that it is the less expensive connection. The disadvantage of inflexibility tends to reserve it for specialized applications, particularly with the overwhelming proliferation of internet-related technology. 3. Packet switching connection: A digital network that groups all transmitted data into suitably-sized packets. Packets are buffered and queued resulting in variable delay and throughput depending on the traffic load in the network.

Some advantages of using a packet switching connection is the bandwidth reservation during the connection establishment, less overhead is required, and network nodes are faster and have higher capacity. A disadvantage of using the packet switching connection is that shared media is accessible over the network. 4. Cell switching connection: A method of statistically multiplexing fixed-length packets to transport data between networks. It is a unreliable, connection-oriented packet switch data protocol.

An advantage of using the cell switching connection is that it is best for simultaneous use of voice and data (for example, VOIP). A disadvantage of using the cell switching connection is that overhead can be considerable. Wide area network technology generally functions at the lower three layers of the OSI reference model: the physical layer, the data link data, and the network layer. The physical layer defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between communicating network systems.

Physical layer specifications define characteristics such as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, and physical connectors. Physical-layer implementations can be categorized as either LAN or WAN specifications. The data link layer provides reliable transit of data across a physical network link. Different data link layer specifications define different network and protocol characteristics, including physical addressing, network topology, error notification, sequencing of frames, and flow control.

Physical addressing (as opposed to network addressing) defines how devices are addressed at the data link layer. Network topology consists of the data-link layer specifications that often define how devices are to be physically connected, such as in a bus or a ring topology. Error notification alerts upper-layer protocols that a transmission error has occurred, and the sequencing of data frames reorders frames that are transmitted out of sequence. Finally, flow control moderates the transmission of data so that the receiving device is not overwhelmed with more traffic than it can handle at one time.

The network layer provides routing and related functions that enable multiple data links to be combined into an internetwork. This is accomplished by the logical addressing (as opposed to the physical addressing) of devices. The network layer supports both connection-oriented and connectionless service from higher-layer protocols. Network-layer protocols typically are routing protocols, but other types of protocols are implemented at the network layer as well.

Some common routing protocols include Border Gateway Protocol (BGP), an Internet inter-domain routing protocol; Open Shortest Path First (OSPF), a link-state, interior gateway protocol developed for use in TCP/IP networks; and Routing Information Protocol (RIP), an Internet routing protocol that uses hop count as its metric. From this technology it opened the door to new ideas and equipment that could support an entire city, along with the type of people that are always “on-the-go”. For the “on-the-go” type of people, technology has introduced to them the WWAN (wireless WAN).

A WWAN differs from WLAN (wireless LAN) in that it uses mobile telecommunication cellular network technologies such as WIMAX, UMTS, GPRS, EDGE, CDMA2000, GSM, CDPD, Mobitex, HSUPA, or 3G to transfer data. It can also use LMDS and Wi-Fi to connect to the internet. These cellular technologies are offered regionally, nationwide, or even globally and are provided by a wireless service provider. WWAN connectivity allows a user with a laptop and a WWAN card to surf the web, check email, or connect to a virtual private network (VPN) from anywhere within the regional boundaries of cellular service.

Various computers now have integrated WWAN capabilities (such as HSDPA in Centrino). This means that the system has a cellular radio (GSM/CDMA) built in, which allows the user to send and receive data. Since radio communications systems do not provide a physically secure connection path, WWANs typically incorporate encryption and authentication methods to make them more secure. Unfortunately some of the early GSM encryption techniques were flawed, and security experts have issued warnings that cellular communication, including WWAN, is no longer secure. UMTS (3G) encryption was developed later and has yet to be broken.


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