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Chapter 9 Computer Networks. Chapter Topics. OSI network layers Network Topology Media access control Addressing and routing Network hardware Network standards. OSI Network Layers. OSI Network Layers.
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Chapter Topics • OSI network layers • Network Topology • Media access control • Addressing and routing • Network hardware • Network standards
OSI Network Layers • Presentation Layer – ensures that data transmitted by one network node is correctly interpreted by the other network node. • Session Layer – establishes and manages communication sessions.
OSI Network Layers • Transport Layer – formats messages into packets suitable for transmission over the network. • Network Layer – routes packet to their proper destination. • Data Link Layer – interface between network software and hardware.
OSI Network Layers • Physical Layer – the layer at which communication between devices actually takes place.
Chapter Topics • OSI network layers • Network Topology • Media access control • Addressing and routing • Network hardware • Network standards
Network Topology • Definition of Network Topology • Point-to-Point transmission • Shared Connections • Store and Forward • Physical Topology (star, bus, ring) • Logical Topology
Network Topology • Network topology refers to: • The spatial organization of network devices. • The physical routing of network cabling. • The flow of message from one network node to another.
Network Topology • Point-to-Point transmission – the line is laid over the shortest path and connected directly to both nodes. Used for small networks. • Shared connections – smaller shared links are connected to larger shared links. Used for larger networks.
Network Topology • Store and Forward - interconnected system of end nodes and transfer points used to route data among end nodes.
Network Topology • Physical topology – refers to the physical placement of cables and device connections to those cables. • Logical topology – refers to the path that messages traverse as they travel from node to node.
Network Topology Physical Topology • Star • Bus • Ring
Network Topology Star Topology • Uses a central node to which all other nodes are connected. • The central node can be a transfer point. • Advantage: simple wiring. • Disadvantage: the failure of the hub disables the entire network.
Network Topology Bus Topology • Connects each node to a common transmission line. • Transmitted messages travel from a node across the common transmission line. • Advantage: simple wiring and low susceptibility to failure.
Network Topology Ring Topology • Connects each network node to two other nodes and the entire network forms a closed loop. • Advantages: long maximum network length and low susceptibility to noise and distortion.
Network Topology Ring Topology • Disadvantages: Susceptibility to failure and difficulty adding , deleting and moving nodes.
Chapter Topics • OSI network layers • Network Topology • Media access control • Addressing and routing • Network hardware • Network standards
Media Access Control • Definition of a Collision • Methods for dealing with Collisions • Carrier Sense Multiple Access with Collision Detection • Token Passing
Media Access Control • Collision – noise or interference in a message. • Methods for dealing with collisions: • Carrier Sense Multiple Access/Collision Detection (CSMA/CD) • Token Passing
Media Access Control Carrier Sense Multiple Access/Collision Detection – (Commonly used on bus network topologies) • A node that wants to transmit listens (carrier sense) until no traffic is detected. • The node then transmits its message.
Media Access Control Carrier Sense Multiple Access/Collision Detection – • The node listens during and immediately after its transmission. If abnormally high signal levels are heard, which is a collision detection, then the node ceases transmission. • If a collision is detected, the node waits for a random time interval and then retransmits its message.
Media Access Control Token Passing • Used in ring network topologies. • A token is passed from node to node. • Only the node with the token can pass a message. • Advantage: simplicity. • Disadvantage: inefficient use of data transfer capacity.
Chapter Topics • OSI network layers • Network Topology • Media access control • Addressing and routing • Network hardware • Network standards
Addressing and Routing • Definition of a Local Area Network • Definition of a Wide Area Network • Local Area Network Routing • Wide Area Network Routing
Addressing and Routing • Local Area Network – a network covering a floor or building. • Wide Area Network – a network a network that spans large physical distances, such as multiple buildings, cities, regions, or continents.
Addressing and Routing Local Area Network Routing • Each time a node is started, it sends a message announcing its presence and its address to the nearest hub. • Each hub maintains a table of addresses and transmission lines or connections ports and uses that table to make routing decisions.
Addressing and Routing Wide Area Network Routing Each router knows: • The addresses and physical locations of its own nodes • Other nearby routers • Groups of addresses that they control • Default destination for messages to the addresses that it does not know
Chapter Topics • OSI network layers • Network Topology • Media access control • Addressing and routing • Network hardware • Network standards
Network Hardware Network Hardware Devices: • Network interface units or network interface cards • Hub • Bridges • Routers • Switches
Technology Focus Home Networks
Chapter Topics • OSI network layers • Network Topology • Media access control • Addressing and routing • Network hardware • Network standards
Network Standards • The Institute of Electrical and Electronic Engineers (IEEE) has drafted a number of telecommunication and network standards – IEEE 803 standards.
Windows Commands • ipconfig • ipconfig /all • net statistics workstation • net use • net view
