COMPUTER NETWORKS. NETWORK TOPOLOGY Network Topology: refers to the spatial organization of network devices, the physical routing of network cabling,

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Slide 1 COMPUTER NETWORKS Slide 2 NETWORK TOPOLOGY Network Topology: refers to the spatial organization of network devices, the physical routing of network cabling, and the flow of messages from one network node to another. Slide 3 Network Topology can refer to physical and logical. Physical topology refers to the physical placement of cables and device connections to those cables Logical topology refers to the path that messages travel from node to node. Slide 4 There are three common types of network topology: Star Bus Ring Slide 5 Star Topology: use a central node to which all other nodes are connected. A central node is a transfer point. Slide 6 Advantage of the star topology is relatively simple wiring connect to the hub. Primary disadvantage of star topology is the failure of the hub disables the entire network. Slide 7 Bus topology connects each node to a common transmission line. And at the end of the bus there is a terminating resistor to absorb signals and prevent them from bouncing back down to the common transmission line. Slide 8 Primary advantage of the bus topology is relatively simply wiring and low susceptibility to failure. There is no central node that can fail and disable the entire network. The fail of any node does not prevent other nodes from transmitting and receiving messages. Slide 9 Ring Topology: connects each node to two other nodes and the entire network forms a closed loop. Message is passed around in one direction. Slide 10 The primary advantage of ring topology are long maximum network length and low susceptibility to noise and distortion. The disadvantage of ring topology are susceptibility to failure and difficulty in adding, deleting, or moving nodes Slide 11 ADDRESSING and ROUTING Slide 12 LAN (Local Area Network): is a network covering a floor or building. Slide 13 WAN (Wide Area Network): is the entire campus network. LANs are interconnected to form WAN Slide 14 Each time the node want to send a message. It sends a message announcing its presence and its address to the nearest hub. Each hub maintains the table of address and transmission lines or connection ports and uses that table to make routing decision. Example Example How message is passed in Local Area Network Routing Slide 15 WAN using router to routes the message. Each router knows address and physical location of its own nodes and knows other nearby routers and the group of addresses that they control. Example Example Wide Area Network Routing. Slide 16 There are 2 categories to avoid collision: CSMA/CD Token passing. Media Access Control Media Access Control (MAC) protocol specifies rules for accessing a shared transmission medium or to avoid Collision. Slide 17 CSMA/CD Collision detection each device monitors its data in case it collides with other data. A collision can occur if two devices listen to the media, decide it is clear and then transmit at the same time. Carrier sensed- each device that wants to send data along the share media listen to the media to detect if it is in use by other users. Multiple access any device can transmit if it detect that media is clear. Slide 18 Slide 19 Token passing Token passing message is passed from node to node and only the node that possesses the token is allowed to transmit messages. Slide 20 NETWORK HARDWARE Network interface units or Network interface card. Hub. Bridges Routers Switches. Slide 21 Network Interface Unit (NIU): is a device that connects a network node such as computer, printer to a network transmission cable. Slide 22 Hub: is used to connect nodes in a LAN. And the transmission lines are connected to an NIU with standard connecter RJ45. Slide 23 Bridge (or repeater): is the device that connects two networks and forwards packets between them. Slide 24 Router: is intelligent bridge that can connect to more than two networks and exchange information to improve routing decisions. Slide 25 Switch: functions similar to a bridge and hub but it has more input connections for computers and other network nodes. A switch determines which computer is intended destination and pass message to that only computer. Slide 26 OSI NETWORK LAYERS OSI: is the international standard that divides network architecture into seven layers and each layer uses the service of layer below. APPLICATION PRESENTATION SESSION TRANSPORTATION NETWORK DATA LINK PHYSICAL Slide 27 Slide 28 TCP/IP TCP/IP (Transmission Control Protocol and Internet Protocol) is a set if protocols designed for supporting global internetworking. Slide 29 TCP: is a connection-oriented protocol provides the framework to check for lost messages by establishing a connection with an intended recipient before transmitting messages. IP accepts packets called datagrams from TCP and other higher session layer protocols. IP translates datagrams into a format suitable for transport by the physical network. Slide 30 IP: is also called connectionless protocol. Because IP sends a datagram to the appreciate gateway and assumes that the datagram will find its way successfully to the intended recipient.. TCP is a connection-oriented protocol. It provides the required framework to check for list messages by establishing a connection with an intended recipient before transmitting messages. Slide 31 TCP connections are established through a port and socket. Port: is a TCP connection with a unique integer number. Socket: is the combination of an IP address and a port number Slide 32 NETWORK STANDARDS The Institute of Electrical and Electronic Engineers (IEEE) has drafted a number of telecommunication and network standards, referred to as the IEEE 802 standards. Slide 33 Slide 34 Application layer: is a program such as Web browser, email client respond to high-level requests for network services. Back Slide 35 Presentation Layer: ensures that data transmitted by one network node is correctly interpreted by other network node. Back Slide 36 Session Layer: establishes and manages communication sessions. Back Slide 37 Transport Layer: divides messages into packets suitable for transmission over the network and adding a sequence number to each packet. Back Slide 38 Network Layer: routes the packets to the proper destination. It will rout to the nearest LAN hub or router. Back Slide 39 Data Link Layer: is the interface between network software and hardware. It manage packet transfer from secondary or primary to NIU. Back Slide 40 Physical Layer: is the layer at which communication between device actually take place. Back Slide 41 Slide 42


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