Transcript Chapter 1 Computer Technology: Your Need to Know

Chapter 9
Computer Networks
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Chapter Topics
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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
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Presentation Layer – ensures that data
transmitted by one network node is correctly
interpreted by the other network node.
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Session Layer – establishes and manages
communication sessions.
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OSI Network Layers
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Transport Layer – formats messages into
packets suitable for transmission over the
network.
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Network Layer – routes packet to their
proper destination.
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Data Link Layer – interface between network
software and hardware.
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OSI Network Layers
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Physical Layer – the layer at which
communication between devices actually
takes place.
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Mathieson’s Three Layers
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Chapter Topics
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OSI network layers
Network Topology
Media access control
Addressing and routing
Network hardware
Network standards
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Network Topology
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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
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Network topology refers to:
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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
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Point-to-Point transmission – the line is laid
over the shortest path and connected directly
to both nodes. Used for small networks.
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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
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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
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Physical topology – refers to the physical
placement of cables and device connections
to those cables.
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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
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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
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OSI network layers
Network Topology
Media access control
Addressing and routing
Network hardware
Network standards
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Media Access Control
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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
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Collision – noise or interference in a
message.
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Methods for dealing with collisions:
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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)
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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 –
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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.
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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
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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
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OSI network layers
Network Topology
Media access control
Addressing and routing
Network hardware
Network standards
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Addressing and Routing
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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
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Local Area Network – a network covering a
floor or building.
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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
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Each time a node is started, it sends a
message announcing its presence and its
address to the nearest hub.
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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:
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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
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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
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OSI network layers
Network Topology
Media access control
Addressing and routing
Network hardware
Network standards
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Network Standards
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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
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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.
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LANs are interconnected to form WANs.
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Summary
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A media access control (MAC) protocol
specifies rules for accessing a shared
transmission medium.
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Network hardware devices include NIUs,
hubs, bridges, routers, and switches.
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Summary
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The Open Systems Interconnection (OSI)
model is an ISO conceptual model that
divides network architecture into seven
layers.
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TCP/IP is the core Internet protocol suite.
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The IEEE 802 standards cover many types of
networks.
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