Transcript Semester 1 Chapter 3 Lecture 1

Institute of Technology Sligo - Dept of Computing
LAN Maps & Symbols
Topologies & Devices
Paul Flynn
Institute of Technology Sligo - Dept of Computing
By the end of this
Chapter, you will be
able to name and
describe all the symbols
in this diagram.
Institute of Technology Sligo - Dept of Computing
Physical & Logical Topologies

Physical Topologies define the actual
layout of the wire (media).


For example, this classroom’s wiring is
laid out in an extended star
Logical Topologies define how the
media is accessed by the hosts.

For example, in this classroom hosts
access the media on a first come, first
served basis
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Physical Topologies
Bus
Extended
Star
Ring
Hierarchical
Star
Mesh
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Bus Topology

Single backbone

All hosts directly
connected to backbone

Each end of the bus
must be properly
terminated
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Ring Topology

No backbone

A host is directly
connected to each of its
neighbors

Used for token passing
logical topologies
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Star Topology

All devices connected to
a central point

Center of star is usually
a hub or a switch

Used for Ethernet
technologies
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Extended Star Topology

Connects individual star
topologies together.

At the center of the star
is a hub or a switch.

Extends the length and
size of the network.

This is the topology we
are using in our lab!
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Hierarchical Topology
Server

Like the extended star
except a computer
controls traffic—not a
hub or a switch.
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Mesh Topology

Each host has its own
connection to every
other host

Used in situations where
communication must not
be interrupted.
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Logical Topologies

Broadcast Topology



Each host on the LAN sends its data (or
broadcasts its data) to every other host.
Access to media is based of “first-come,
first-serve.” (Ethernet works this way)
Token Passing Topology


Access to media is controlled by an
electronic token.
Possession of the token gives the host the
right to pass data to its destination.
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LAN Media Symbols
Token
Ring
Ethernet
Line
FDDI
Ring
Serial
Line
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LAN Device Symbols—Layer
1
Repeater
Transceiver
Hub
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LAYER 1—Repeater

Cleans up (regenerates) and repeats the
signal.

Used when a network’s cabling extends
beyond its capability.
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LAYER 1—Transceiver
Cat 5 UTP
Fiber

Transmitter and Receiver of electronic
signals—specialized repeater.

Connects different media technologies

Also called a MAU (Media Attachment
Unit)
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LAYER 1—Hub
The Cloud

Simply a multi-port repeater.

Used to connect multiple devices to the
same network drop.
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LAN Device Symbols—Layer
2
Bridge
Switch
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LAYER 2—Bridge

Connects two LAN segments.

Keeps traffic local by filtering traffic
based on MAC Addresses.
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LAYER 2—Switch
The Cloud

Connects multiple LAN segments.

Can be called a multi-port bridge.

Provides full bandwidth out each port.
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LAN Device Symbols—Layer
3
Router
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LAYER 3—Router
The Cloud

Can be used to connect different Layer 2
devices and different topologies.

Makes decisions based on network addresses
(IP Addresses).

What are the routers two main functions?
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Router’s Two Main Functions

Path Determination

Packet Switching
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Router’s Two Main Functions
Path Determination is the process of
evaluating a packet’s destination IP
address so that the router can decide
which port to send out the packet.
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Router’s Two Main Functions
In Packet Switching, the router reencapsulates the packet in the protocol
needed for the specified port and then
switches the packet out that port.
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The Cloud
The Cloud

The cloud is a collection of devices that
operate at all levels (7-1) of the OSI model.

The cloud is used to represent a large group
of details that are not pertinent to a situation
or description, at a given time.

The cloud helps remind us that our
discussions are about various parts of a
larger interconnected network—The Internet!
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Engineering Journal Assignment
Draw freehand the Teaching Topology found in
the second graphic on Screen 3.1.1 (shown
below). As you draw it, test your knowledge
about the various topologies and devices.