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Communications and Networks Copyright©2008 N.AlJaffan®KSU 1 Communications and Networks Five general concepts provide the basis for the relationship between the communicating devices: line configuration. Topology. Network Architectures Internetworks. Copyright©2008 N.AlJaffan®KSU 2 Communications and Networks Line configuration Its refers to the way two or more communication devices attach to a link. Link is the physical communication pathway that transfers data from one device to another. There are two possible line configurations point-to-point multipoint Copyright©2008 N.AlJaffan®KSU 3 Communications and Networks Copyright©2008 N.AlJaffan®KSU 4 Communications and Networks Point-to-Point It is provides a dedicated link between two devices. The entire capacity of the channel is reserved for transmission between those two devices. Copyright©2008 N.AlJaffan®KSU 5 Communications and Networks Multipoint Copyright©2008 N.AlJaffan®KSU 6 Communications and Networks Multipoint also called multidrop It is one in which more than two specific devices share a single link. The capacity of the channel is shared, either spatially or temporally. If several devices can use the link simultaneously, it is spatially line configuration. If users must take turns, it is a time-shared line configuration. Copyright©2008 N.AlJaffan®KSU 7 Communications and Networks Topology The term topology refers to the way a network is laid out. There are 5 basic topologies possible: Mesh Star Tree Bus Ring Copyright©2008 N.AlJaffan®KSU 8 Communications and Networks Mesh Copyright©2008 N.AlJaffan®KSU 9 Communications and Networks Mesh Every device has a dedicated point –to-point link to every other device. A fully connected mesh network therefore has n(n-1)/2 physical channels to link n devices. Every device on the network must have n-1 input/output (I/O) ports. Copyright©2008 N.AlJaffan®KSU 10 Communications and Networks Mesh Advantages 1. Eliminating the traffic problems that can occur when links must be shared by multiple devices. 2. It is robust. it one link becomes unusable, it does not incapacitate the entire system. 3. It is privacy or security. 4. Point-to-point links make fault identification and fault isolation easy. Copyright©2008 N.AlJaffan®KSU 11 Communications and Networks Mesh disadvantages 1. Installation and reconfiguration are difficult. 2. The sheer bulk of the wiring can be greater than the available space can accommodate. 3. The hardware required to connect each link ( I/O ports a cable) can be expensive. Copyright©2008 N.AlJaffan®KSU 12 Communications and Networks Star Copyright©2008 N.AlJaffan®KSU 13 Communications and Networks Star Each device (node) has a dedicated point-to-point link only to a central controller, usually called Hub. Advantages 1. 2. 3. 4. It is less expensive than a mesh topology. It is easy to install and maintain. It is robustness. If one node fails, only that node is affected. Easy fault identification and fault isolation. It has one disadvantage if the hub fails, the entire network is inoperable until the hub is repaired. Copyright©2008 N.AlJaffan®KSU 14 Communications and Networks Tree Copyright©2008 N.AlJaffan®KSU 15 Communications and Networks Tree Is a variation of a star. nodes in a tree are linked to a central hub that controls the traffic to the network. Not every device plugs directly into the central hub. The majority of devices connect to a secondary hub that in turn is connected to the central hub. Copyright©2008 N.AlJaffan®KSU 16 Communications and Networks Tree The central hub in the tree is an active hub, which contains a repeater. The secondary hubs may be active or passive hubs. A passive hub provides a simple physical connection between the attached devices. Copyright©2008 N.AlJaffan®KSU 17 Communications and Networks Tree It allows more devices to be attached to a single central hub and can increase the distance a signal can travel between devices. It allow the network to isolate and prioritize communications from different computers. Copyright©2008 N.AlJaffan®KSU 18 Communications and Networks Bus Copyright©2008 N.AlJaffan®KSU 19 Communications and Networks Bus Consists of a single central cable, to which all computers and other devices connect. The bus in a bus network transmits data, instruction and information in both directions. Bus network are popular on LANs because they are inexpensive and easy to install. Copyright©2008 N.AlJaffan®KSU 20 Communications and Networks Bus That failure of one device usually does not affect the rest of the bus network. Difficult reconfiguration and fault isolation. A fault or break in the bus cable stops all transmission, even between devices on the same side of the problem. Copyright©2008 N.AlJaffan®KSU 21 Communications and Networks Ring Copyright©2008 N.AlJaffan®KSU 22 Communications and Networks Ring A cable forms a closed loop (ring) with all computers and devices arranged along the ring. Data transmitted on a ring network travels from device to device around the entire ring, in one direction. If a computer or device on a ring network fails, all devices before the failed device are unaffected, but those after the failed device cannot function. It can span a larger distance than a bus network, but it is more difficult to install. Copyright©2008 N.AlJaffan®KSU 23 Communications and Networks Hybrid topologies It is a network combines several topologies as subnetworks linked together in a larger topology. Copyright©2008 N.AlJaffan®KSU 24 Communications and Networks Network Architectures CLINET/SERVER PEER TO PEER INTERNET PEER TO PEER (P2P) Copyright©2008 N.AlJaffan®KSU 25 Communications and Networks Network Architectures CLINET/SERVER one or more computer as a server; the other computers on the network request services from the server. Its provides an efficient means to connect 10 or more computers. Most client/server networks require a person to serve as a network administrator because of the large size of the network Copyright©2008 N.AlJaffan®KSU 26 Communications and Networks Network Architectures PEER-TO-PEER One type of peer-to-peer network is a simple, inexpensive network that typically connects fewer than10 computer. 1. Each computer, called a peer, has equal responsibilities and capabilities. 2. Sharing hardware as a printer, data, or information with other computers on the peer-to-peer network. 3. Each computer on the network contains both the network operating system and application software. 4. Each computer stores files on its own storage devices. Copyright©2008 N.AlJaffan®KSU 27 Communications and Networks Network Architectures Internet PEER-TO-PEER ( P2P ) Another type of peer-to-peer. Describe an Internet network. sometimes is called a file sharing network because users with compatible SW and an internet connection copy files from someone else’s HD to their HD. example of networking SW that support P2P are BitTorrent, Grokster, Gunutella and Kazaa, which allow users to swap MP3 music and other files via the web Copyright©2008 N.AlJaffan®KSU 28 Communications and Networks Categories of networks Into which category a network falls is determined its size, ownership, the distance it covers and its physical architecture. LAN a Local area network MAN WAN Copyright©2008 N.AlJaffan®KSU 29 Communications and Networks LAN a Local area network Is a network that connects computers and devices in a limited geographical area such as a home, school computer laboratory, office building, or closely positioned group of buildings. Is usually privately owned. It use only one type of transmission media (often are connected via cable ) and topology. Wireless LAN ( WLAN ) is a LAN that uses no physical wires. Copyright©2008 N.AlJaffan®KSU 30 Communications and Networks Copyright©2008 N.AlJaffan®KSU 31 Communications and Networks MAN a metropolitan area network Is a high-speed network that connects local area network in a metropolitan area such as a city or town and handles the bulk of communications activity across that region. MAN typically includes one or more LANs, but covers a smaller geographic area than a WAN. Its usually is managed by consortium of users or by single network provider that sell the service to the users. Copyright©2008 N.AlJaffan®KSU 32 Communications and Networks Copyright©2008 N.AlJaffan®KSU 33 Communications and Networks WAN a wide area network Is a network that covers a large geographic area such as country, or the world. Using a communications channel that combines many types of media such as telephone lines, cables, and radio waves. A WAN can be one large network or can consist of two or more LANs connected together. The Internet is the world's largest WAN Copyright©2008 N.AlJaffan®KSU 34 Communications and Networks Copyright©2008 N.AlJaffan®KSU 35 Communications and Networks Internetworks If 2 or more networks are connected, they become an internetwork, or internet. Individual networks are joined into internetworks by the use of interworking devices. These devices, which include routers and gateways. The term internet should not be confused with Internet. internet used to mean an interconnection of networks. Internet is the name of specific worldwide network. Copyright©2008 N.AlJaffan®KSU 36 Communications and Networks R LAN LAN R R R WAN R R R LAN LAN R Copyright©2008 N.AlJaffan®KSU 37