Huda AL-Omair_ networks61 Wide Area Network

Huda AL-Omair_ networks62 What is a WAN? Wide area network or WAN is a computer network covering a wide geographical area, involving a vast array of computers. The best examples is the internet.

Huda AL-Omair_ networks63 WAN Users WANs are used to connect local area networks (LANs) together, so that users and computers in one location can communicate with users and computers in other locations. Many WANs are built for one particular organization and are private. Others, built by Internet service providers, provide connections from an organization's LAN to the Internet.

Huda AL-Omair_ networks64 How to build a WAN? WANs are most often built using leased lines. A set of switches and routers are interconnected to form a Wide Area Network.

Huda AL-Omair_ networks65 WAN Technology Point-to-Point Connection Switched Networks Packet Switching Circuit Switching

Huda AL-Omair_ networks66 1- Point-to-Point Connection Uses leased lines It is a permanent full time connection, user has exclusive use. Sending types: Datagram transmission : Sending by packets Data stream transmission : Sending by bytes Advantage: Line is always reserved for the user Disadvantage: Expensive

Huda AL-Omair_ networks67 2- Switched Network Switched network - Several users share the same line or the bandwidth of the line. There are two types of switched networks: –Circuit switching –Packet switching

Huda AL-Omair_ networks Packet Switching It breaks data down into small packets to be sent across the network. Allows users to share common carrier resources so that the carrier can make more efficient use of its infrastructure. Examples of packet switching technologies:X.25, ATM, Frame relay Advantages: –Fast, but slower than circuit switching. –Cheap –Connection is always there, due to many paths that data can move through.

Huda AL-Omair_ networks69 WAN Protocols X.25: This set of protocols allows computers on different public networks to communicate through an intermediary computer at the network layer level. These protocols use a great deal of error checking for use over unreliable telephone lines. Their speed is about 64Kbps. Used with packet switching

Huda AL-Omair_ networks610 WAN Protocols Frame Relay: (FR). A high-speed packet-switched data communications service, similar to X.25. Frame Relay is the successor to the X.25 protocol and is faster because it has shed some of the error-checking functions that slowed the packet-switching capabilities of X.25. Frame Relay - Error checking is handled by devices at both sides of the connection. Frame relay uses frames of varying length and it operates at the data link layer of the OSI model Frame relay speed is between 56Kbps and 1.544Mbps. Frame relay does not store data and has less error checking than X.25. Used with packet switching

Huda AL-Omair_ networks611 WAN Protocols ATM: Asynchronous Transfer Mode A dedicated-connection switching technology that organizes digital data into 53-byte cell units. Individually, a cell is processed asynchronously relative to other related cells and is queued before being multiplexed over the transmission path.. May be used over a variety of media with both base band and broadband systems. It is used for audio, video, and data. It uses hardware devices to perform the switching of the data. Speeds from 155Mbps to 622 Mbps are achieved. Error checking is done at the receiving device, not by ATM. Used with packet switching

Huda AL-Omair_ networks Circuit Switching Circuit Switching allows data connections to be established when needed and then terminated when communication is complete. This works like a normal telephone line works for voice communication. Cost is determined by the connection time. Examples: ISDN,DSL Advantage: Cheap Disadvantage: Network is reserved for the connection even if no data is sent. Any failure in circuits will stop the connection, and require another call to reserve a new circuits. Some times you wait until network is ready.

Huda AL-Omair_ networks613 Integrated Services Digital Network (ISDN) ISDN is available from local phone providers and takes advantage of digital phone switching systems. The cost of an ISDN connection will be dictated by how often the line is used for data transfer. Your usage charge is determined by the connection charge (and there is also often a recurring monthly charge for being connected to the service).

Huda AL-Omair_ networks614 Digital Subscriber Line (DSL) ISDN is rapidly being eclipsed by DSL connections. DSL offers voice and data communication over the regular phone lines with speeds of up to 7Mbps. The data and voice communication can take place simultaneously over the very same phone line. DSL shares the line with the analog voice signal by using a different frequency for the digital data (that is sent and received using the line). This means you can make a phone call while sending data over the line.

Huda AL-Omair_ networks615 WAN and OSI WAN technologies generally function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer.

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