Chapter 9 Computer Networks

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Chapter 9Computer Networks
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Chapter Topics

• OSI network layers
• Network Topology
• Media access control
• Addressing and routing
• Network hardware
• Network standards

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OSI Network Layers
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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.

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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.

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OSI Network Layers

• Physical Layer the layer at which communication
  between devices actually takes place.

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Mathiesons Three Layers
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Chapter Topics

• OSI network layers
• Network Topology
• Media access control
• Addressing and routing
• Network hardware
• Network standards

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Network Topology

• Definition of Network Topology
• Point-to-Point transmission
• Shared Connections
• Store and Forward
• Physical Topology (star, bus, ring)
• Logical Topology

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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.

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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.

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Network Topology
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Network Topology

• Store and Forward - interconnected system of end
  nodes and transfer points used to route data
  among end nodes.

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Network Topology
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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.

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Network Topology

• Physical Topology
• Star
• Bus
• Ring

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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.

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Network Topology
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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.

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Network Topology
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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.

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Network Topology

• Ring Topology
• Disadvantages Susceptibility to failure and
  difficulty adding , deleting and moving nodes.

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Network Topology
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Network Topology
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Network Topology
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Chapter Topics

• OSI network layers
• Network Topology
• Media access control
• Addressing and routing
• Network hardware
• Network standards

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Media Access Control

• Definition of a Collision
• Methods for dealing with Collisions
• Carrier Sense Multiple Access with Collision
  Detection
• Token Passing

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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

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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.

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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.

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Media Access Control
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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.

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Chapter Topics

• OSI network layers
• Network Topology
• Media access control
• Addressing and routing
• Network hardware
• Network standards

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Addressing and Routing

• Definition of a Local Area Network
• Definition of a Wide Area Network
• Local Area Network Routing
• Wide Area Network Routing

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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.

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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.

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Addressing and Routing
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Addressing and Routing
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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

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Chapter Topics

• OSI network layers
• Network Topology
• Media access control
• Addressing and routing
• Network hardware
• Network standards

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Network Hardware

• Network Hardware Devices
• Network interface units or network interface
  cards
• Hub
• Bridges
• Routers
• Switches

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Network Hardware
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Technology Focus

• Home Networks

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TCP/IP
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Chapter Topics

• OSI network layers
• Network Topology
• Media access control
• Addressing and routing
• Network hardware
• Network standards

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Network Standards

• The Institute of Electrical and Electronic
  Engineers (IEEE) has drafted a number of
  telecommunication and network standards IEEE
  803 standards.

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Network Standards
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Technology Focus - Ethernet
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Technology Focus - Ethernet
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Windows Commands

• ipconfig
• ipconfig /all
• net statistics workstation
• net use
• net view

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Summary

• 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.
• LANs are interconnected to form WANs.

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Summary

• A media access control (MAC) protocol specifies
  rules for accessing a shared transmission medium.
• Network hardware devices include NIUs, hubs,
  bridges, routers, and switches.

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Summary

• The Open Systems Interconnection (OSI) model is
  an ISO conceptual model that divides network
  architecture into seven layers.
• TCP/IP is the core Internet protocol suite.
• The IEEE 802 standards cover many types of
  networks.