1. Chapter 4

2.  Understand network connectivity.  Peer-to-Peer network & Client-Server network  Understand network topology  Star, Bus & Ring topology  Understand congestion control techniques  Network equipment Prepared by Saher H. Mohammed 2

3.  The arrangement of nodes (hosts, machines, computers, printers, etc.) is called topology.  The way the networks are arranged, constructed is called topology. Node 1 Node 2 This is called a n = 2 network If both the nodes are computers, then it is called a point-to-point network 3 Prepared by Saher H. Mohammed

4.  Network consist of two or more nodes, connected by one or more channels.  When many computers and peripherals are connected to a common communication channel, it is called a multi-point network or multi-node network. Node 1 Node 4 Node 2 Node 3 Printer 4 Prepared by Saher H. Mohammed

5.  Any devices such as a hard disk or printer that are accessed and used by all the nodes on the network are called shared resources.  Two kinds of relationship exist between the connected nodes  Peer-to-Peer network.  Cooperative processing.  Distributed processing.  Client – Server network. 5 Prepared by Saher H. Mohammed

6.  In a Peer-to-Peer network, all the computers in the network are of same standing (level) and neither is a master or a slave (Server- Client).  A way to enhance the use of resources is cooperative processing, the sharing of processing tasks between two or more processors, either within or between computers.  Distributed processing is the dispersion of the data processing among computers in multiple sites. 6 Prepared by Saher H. Mohammed

7.  In Client - Server relationship, the nodes are not equal. One node is the Server (master) and the rest of the nodes are Clients (slave).  All the clients request service from the server, such as file space, common printer, and shared processing. 7 Prepared by Saher H. Mohammed

8. Hub Client Server 8 Prepared by Saher H. Mohammed

9.  In the client – server architecture, if the clients have no storage nor the processing capabilities, then the clients are called dumb terminal.  Example old mainframes systems.  In current client – server architecture, most of the clients have processing capabilities. 9 Prepared by Saher H. Mohammed

10.  The client – server architecture is the basis for the current day Local Area Networks and Wide Area Network.  In client – server architecture, the client can be of two types  Thin Client – they have very limited processing and storage capabilities.  Example – Smart phones.  Fat Client – they have large storage and processing capabilities.  Example – Desktop and Laptops. 10 Prepared by Saher H. Mohammed

11. Hub Client - Laptop Client – Smart phone Client - IPad Client - Desktop Client - Laptop Server 11 Prepared by Saher H. Mohammed

12.  Advantages  Resource sharing.  Share processing.  Easy maintenance. 12 Prepared by Saher H. Mohammed

13.  Network Operation systems  Example Microsoft Windows 2003/2008 Server OS.  A networking device  Hub, Switch, Router.  Network Interface Card (NIC)  Media (Wire) CATegoryDefiniti on MeansUsage 310Base T 10 Mbps on baselineEthernet 5100Base T 100 Mbps on baselineFast Ethernet 61000Bas eT 1000 Mbps on baseline Giga Ethernet 13 Prepared by Saher H. Mohammed

14.  Geographical arrangement of a network’s components is also called a topology.  Topology can be of two types  Physical Topology – how the wiring is laid out.  Electrical Topology – how the nodes use the path. 14 Prepared by Saher H. Mohammed

15.  The most common type of the network topology.  All the cables from the end nodes (clients and server) are connected to a central point – Hub or a Switch. Client - PC Client - Laptop Client - Scanner Client - Printer Client - PC Active Node Client Server Client Hub 15 Prepared by Saher H. Mohammed

16.  In the star topology, the end nodes acquire the attention of the central node before communication can take place, this process is called polling.  One disadvantage of star topology is congestion.  If the central active node is busy, then the network becomes congested. 16 Prepared by Saher H. Mohammed

17.  In a bus topology, all the nodes are connected to a single, central wire called as bus.  One major drawback of a bus topology is the single point of failure.  If the central wire fails, then the entire network breaks down. 17 Prepared by Saher H. Mohammed

18. Client Server Client 18 Prepared by Saher H. Mohammed

19.  In the ring topology, each node is connected to the one above node and the one below node.  All the messages pass around the ring and each transmitted node will see part of the message.  In order to transmit, a node must possess a token.  At any time, only one node can have a token. 19 Prepared by Saher H. Mohammed

20. Client Server Client 20 Prepared by Saher H. Mohammed

21.  Collision occurs when two or more nodes transmit at the same time.  Collision can make all the communication in the network to stop.  There are two methods of collision control  Collision Avoidance.  Collision Detection. 21 Prepared by Saher H. Mohammed

22.  In a star topology, all the end nodes are connected to a central node. So, before communicating, the end nodes must get the attention of the central node – polling.  Central node will poll/ query all the end nodes to check if some end node is ready to transmit or the central node is ready to receive any message from the end nodes.  The end nodes will poll/ query the central node to signal that they are ready to transmit, and will wait till the central node is ready. 22 Prepared by Saher H. Mohammed

23.  Only one node in the ring topology will have the token, only that node will have the permission to send the messages.  Once the node is finished with sending the message, it will release the token for the other nodes to use.  In the ring topology, messages are passed from one node to the next until the messages reaches the destination. 23 Prepared by Saher H. Mohammed

24.  Collision detection – react to the collisions, instead of avoiding it.  The bus topology uses carrier sense multiple access/ collision detection (CSMA/ CD).  Carrier sense is the primary way of gaining the access to the central wire/ bus. 24 Prepared by Saher H. Mohammed

25.  The node willing to transmit will sense the carrier (central wire). If there are no signals on the carrier, the node will broadcast the message.  All the nodes in the network will get the message, but only the correct recipient will be able to access the message. 25 Prepared by Saher H. Mohammed

26.  To build a network, certain networking devices are used  Repeater.  Hub.  Switch.  Router.  Gateway.  Bridge. 26 Prepared by Saher H. Mohammed

27.  A repeater is a simple hardware device that receives a weak signal and regenerates it.  Since the repeater creates a new signal, the distortion or attenuation is removed and the signal is made stronger.  Repeaters are used at Layer 1( Physical) of the OSI Model.  Repeaters are generally used to extend the coverage of a network by extending the length of the segment. 27 Prepared by Saher H. Mohammed

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29.  A hub is a hardware device that physically connects multiple cables, providing a common connection point.  Hubs are passive devices. They will forward a message to all the nodes connected via the ports.  Hubs will divide the bandwidth among all the nodes.  Hubs are used at Layer 1( Physical) of the OSI Model. 29 Prepared by Saher H. Mohammed

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31.  A switch is a special type of hub.  A switch is an active device.  Switch operates at the second layer (DLL) of OSI model.  A switch will forward the packets only the correct destination.  A switch will not divide the bandwidth, thus the transmission speed is higher. 31 Prepared by Saher H. Mohammed

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33.  A bridge is software or a hardware device that connects two LAN’s or two segments of the same LAN.  Bridge is a layer 2 (DLL) device.  Two LAN’s or the two segments of the same LAN must use the same data link protocol.  Example (Ethernet, Token, Ring) 33 Prepared by Saher H. Mohammed

34.  Transparent Bridge: Connects two LAN’s that use the same data link protocol.  Ethernet network– Ethernet network.  Token ring network – Token ring network.  Translating Bridge: Connects two LAN’s that use different data link protocol.  Ethernet network– Token ring network.  Token ring network – Ethernet network. 34 Prepared by Saher H. Mohammed

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36.  Routers are hardware devices used to forward the data packets between different networks.  Routers intelligent devices, they have routing protocols and store the path information in the routing tables.  Routers operate at the third layer (Network) of OSI model. 36 Prepared by Saher H. Mohammed

37.  Routers can be static or dynamic.  Static – the routing table cannot be changes.  Dynamic – the routing table can change depending on the situation to find the next best route. 37 Prepared by Saher H. Mohammed

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39.  A gateway is a node on a network that serves as an entrance to another network.  Gateway is a device that uses software to connect networks with different architecture by performing protocol conversion at the application level.  Gateway operates at all the 7 layers of the OSI Model. 39 Prepared by Saher H. Mohammed

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41. Network DeviceOSI Layer RepeaterLayer 1 – Physical Layer HubLayer 1 – Physical Layer SwitchLayer 2 – Data Link Layer BridgeLayer 2 – Data Link Layer RouterLayer 3 – Network Layer GatewayAll 7 Layers 41 Prepared by Saher H. Mohammed

42. Gateways Routers Switches Going up from switches – Routers – Gateways, the capabilities, complexities and the cost increases. 42 Prepared by Saher H. Mohammed

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