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Transcript
Chapter 9
Computer Networks
1
Chapter Topics
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OSI network layers
Network Topology
Media access control
Addressing and routing
Network hardware
Network standards
2
OSI Network Layers
3
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.
4
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.
5
OSI Network Layers

Physical Layer – the layer at which
communication between devices actually
takes place.
6
Mathieson’s Three Layers
7
Chapter Topics
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OSI network layers
Network Topology
Media access control
Addressing and routing
Network hardware
Network standards
8
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
9
Network Topology

Network topology refers to:
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
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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.
10
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.
11
Network Topology
12
Network Topology

Store and Forward - interconnected system
of end nodes and transfer points used to
route data among end nodes.
13
Network Topology
14
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.
15
Network Topology
Physical Topology
 Star
 Bus
 Ring
16
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.
17
Network Topology
18
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.
19
Network Topology
20
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.
21
Network Topology
Ring Topology

Disadvantages: Susceptibility to failure and
difficulty adding , deleting and moving nodes.
22
Network Topology
23
Network Topology
24
Network Topology
25
Chapter Topics






OSI network layers
Network Topology
Media access control
Addressing and routing
Network hardware
Network standards
26
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
27
Media Access Control

Collision – noise or interference in a
message.

Methods for dealing with collisions:

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Carrier Sense Multiple Access/Collision Detection
(CSMA/CD)
Token Passing
28
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.
29
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.
30
Media Access Control
31
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.
32
Chapter Topics






OSI network layers
Network Topology
Media access control
Addressing and routing
Network hardware
Network standards
33
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
34
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.
35
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.
36
Addressing and Routing
37
Addressing and Routing
38
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
39
Chapter Topics

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



OSI network layers
Network Topology
Media access control
Addressing and routing
Network hardware
Network standards
40
Network Hardware
Network Hardware Devices:
 Network interface units or network interface
cards
 Hub
 Bridges
 Routers
 Switches
41
Network Hardware
42
Technology Focus
Home Networks
43
TCP/IP
44
Chapter Topics
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

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

OSI network layers
Network Topology
Media access control
Addressing and routing
Network hardware
Network standards
45
Network Standards

The Institute of Electrical and Electronic
Engineers (IEEE) has drafted a number of
telecommunication and network standards –
IEEE 803 standards.
46
Network Standards
47
Technology Focus - Ethernet
48
Technology Focus - Ethernet
49
Windows Commands
ipconfig
 ipconfig /all
 net statistics workstation
 net use
 net view

50
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.
51
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.
52
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.
53