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Local Area Network (LAN)
DigiPoints, Volume 1
Page 10.1
Student Workbook
DigiPoints Volume 1
Student Workbook
Module 10 – Local Area Network (LAN)
Summary
This module describes the -peed data networks found on customers’ premises that make
possible connections at speeds in excess of 10 Mbps between users, computers, servers,
databases, and other peripherals.
Module Objectives
Upon successful completion of the module, the student should be able to:
•
•
•
•
•
Describe the four basic components of a LAN.
Compare the various topologies used in LAN systems.
Identify the generic hardware components found on a LAN.
Describe the LAN protocols that make it possible to move information across a LAN.
Describe common LAN implementations.
Prerequisites
Read DigiPoints, Volume 1, Chapter 10.
SCTE
Local Area Network (LAN)
DigiPoints, Volume 1
Page 10.2
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Basic LAN Components
•
•
•
•
User Work Station
Protocol Control
Medium Interface
Physical Path
What is an example of a User Work Station?
What type of equipment might be found composing the Physical Path?
SCTE
Local Area Network (LAN)
DigiPoints, Volume 1
Page 10.3
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Bus Topology
Basic
Legend
=
=
Connected via repeaters
Device on LAN
Repeater
Is the Bus a two-way communications path?
What do the repeaters make possible?
What are the limitations or disadvantages of having repeaters?
SCTE
Local Area Network (LAN)
DigiPoints, Volume 1
Page 10.4
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Star Topology
Legen
d
=
Name an advantage of the Star topology.
Name a disadvantage.
SCTE
Device on
LAN
Local Area Network (LAN)
DigiPoints, Volume 1
Page 10.5
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Ring Topology
Star
Ring Star
Legend
=
Device on LAN
=
Centralized Repeater
In how many directions does the ring transmit?
How does the design of a ring prevent collisions of data packets?
What is a Star Ring?
To what type of errors are rings susceptible?
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Local Area Network (LAN)
DigiPoints, Volume 1
Page 10.6
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Tree Topology
What type of network does this resemble?
Why does this sort of network not work well with baseband LANs?
How can the CATV industry overcome this particular problem?
SCTE
Local Area Network (LAN)
DigiPoints, Volume 1
Page 10.7
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Mesh Topology
Legend
=Device on LAN
= Repeater
How are Mesh networks formed?
What is an advantage of a Mesh topology?
Discuss another advant age.
SCTE
Local Area Network (LAN)
DigiPoints, Volume 1
Page 10.8
Student Workbook
LAN Hardware
• Bridges
•
•
Layer 2 of OSI
5 Functions
• Routers
•
•
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Layer 3 of OSI
Connects dissimilar networks
Firewall function
• Brouters
• Gateways
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Bi-directional
Protocol conversions
• Protocol Converters
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Terminal emulation
File transfer in one direction
How are Gateways and Routers similar? Different?
How do Routers and Bridges differ?
What is the difference between a Gateway and a Protocol Converter?
Is there a standard definition for a router, bridge, or gateway?
SCTE
Local Area Network (LAN)
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Page 10.9
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LAN Operating System
Network Operating System
• Supplements OS of PC/Computers on System
• Installed on Network Server
• Multi-Tasking & Multi-User
• Administration, diagnostics, administration, support
What is the purpose of the NOS?
Must servers be special, separate computers?
What are some of the characteristics and features of an advanced NOS?
SCTE
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DigiPoints, Volume 1
Page 10.10
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LAN Protocols
OSI
LAYERS
3-7
IEEE 802.1 INTERNETWORKING
lOGICAL
LINK
CONTROL
(LLC)
IEEE 802.2
TYPE 1 - UNACKNOWLEDGED CONNECTIONLESS SERVICE
TYPE 2 - CONNECTION MODE SERVICE
TYPE 3 - ACKNOWLEDGED CONNECTIONLESS SERVICE
OSI
LAYER 2
MEDIUM
ACCESS
CONTROL
(MAC)
PHYSICAL
802.3
CSMA/CD
(ETHERNET)
BASEBAND
COAXIAL AND
UNSHIELDED
TWISTED PAIR
BROADBAND
COAXIAL
802.4
TOKEN BUS
802.5
TOKEN RING
BROADBAND
COAXIAL
OPTICAL
FIBER
SHIELDED
OR
UNSHIELDED
TWISTED PAIR
How does the IEEE 802.1 protocol differ from the OSI Model?
What are the functions of the LLC?
What type of connects can be found here?
SCTE
802.6
DQDB
(MAN)
OPTICAL
FIBER
OR
COAXIAL
CABLE
OSI
LAYER 1
Local Area Network (LAN)
DigiPoints, Volume 1
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What are the functions of the MAC?
What type of media does the physical layer of the 802.1 standard cover?
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LLC and MAC Layer PDUs
USER DATA
LLC HEADER
DSAP
SSAP
LLC PDU
CONTROL
MAC HEADER
MAC TRAILER
MAC FRAME
NOTES: DSAP = DESTINATION SERVICE ACCESS POINT
SSAP = SOURCE SERVICE ACCESS POINT
CONTENTS OF MAC HEADER AND TRAILER DEPEND ON PARTICULAR MAC
LAYER TECHNOLOGY
How is information being communicated between the layers in 802.1?
What is the purpose of the LLC Header?
What type of information is being added in the MAC layer?
SCTE
Local Area Network (LAN)
DigiPoints, Volume 1
Page 10.13
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Token PDU
Access Control
Start
Delimiter
P
P
P
T
M
P = Priority
T = Token Bit
M = Monitor Bit
R = Reservation Bit
What is the purpose of the Token PDU?
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End
Delimiter
R
R
R
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DigiPoints, Volume 1
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Summary
• Basic components of a LAN
• Topologies
• Hardware
• Operating Systems
• Protocols
• IEEE 802.x and the defined layers
• Basic LAN implementations
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DigiPoints, Volume 1
Page 10.15
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Study Questions
1. Define a Local Area Network.
2. Topology is the word used to describe the interconnection of nodes in a LAN. It can
be used in two ways. To make sure you understand both connotations:
a. What are the four basic topological configurations for LANs?
b. Within any given LAN, what are the three separate topologies, and to what do
they refer?
3. What are the differences between a repeater, a bridge, and a router?
4. What is a Network Operating System, and how does it differ from an Operating
System used in a mainframe or stand-alone PC?
5. What are the protocol layers defined by the IEEE for LANs; what is the function of
each; and how do they map onto the OSI protocol reference model?
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6. What is the IEEE standard corresponding to the type of LAN developed and marketed
by Xerox Corporation, and what is the common name of that type of LAN?
7. What is the IEEE standard corresponding to the type of LAN developed and marketed
by IBM, and what is the common name of that type of LAN?
8. True or False, and why: Logical Link Control is the same for all IEEE-specified
LANs.
9. True or False, and why: Medium Access Control is the same for all IEEE-specified
LANs.
10. Give a general description of how CSMA/CD handles access contention.
11. Give a general description of how a token passing LAN handles access contention.
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Student Workbook
12. Describe the components of a typical high-speed data access system for a service
offering by a cable telecommunications company, and explain how a subscriber is part of
a LAN. In your descriptions, be sure to include the physical form of the digital signal at
the interfaces to each component.
SCTE