1. Introduction to Local Area Networks
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Chapter 1:
Introduction to Local Area Networks
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2. What is a LAN?
A type of network where nodes are connected at high speed in a confined geographical area.
Network: A connection between two or more computers
to exchange data or provide shared access to resources
Node: Any device that can send or receive data via a
network
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3. Why use a LAN?
LANs provide the ability to share resources to other nodes on the network.
Resources include:
Shared files
Shared printers
Shared applications
such as database and
servers
Shared Internet
connection
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4. The First LAN Was built at the Xerox Palo Alto Research Center
(PARC) in 1973.
Xerox PARC was also responsible for the
invention of:
The first personal computer (the Alto)
The first laser printer
The first Graphic User Interface
Although Xerox PARC pioneered many of these
technologies, other companies, such as Apple,
Microsoft, 3Com and Cisco would make them
famous.
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5. Other Types of Networks
Campus area network (CAN): Spans a group of buildings, generally within walking distance of each other that belong
to the same organization.
Metropolitan area network (MAN): Medium speed network that connects sites over distances up to 50 miles. Generally used by organizations that have several locations over the same city. Most MANs can also be described as WANs
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6. Other Types of Networks
WANs are made up of LANs connected by
lower speed long distance links. WANs usually
cover a significant geographical area.
Wide area network (WAN):
WANs use slightly different transmission methods & media and often use a greater variety of technologies than LANs.
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7. LAN vs. WAN Geography – small / large Ownership – self owned / leased
Management – self admin / contract leased
Speed – faster / slower
Cost – hundreds / thousands or millions
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8. Authentication The process by which a user is identified
on the network.
Most frequently accomplished
by means of a logon account
and a password.
Each user must have a valid logon account on the
computer or network to be authenticated. Sometimes
authentication is centralized and sometimes each
resource requires individual authentication.
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9. Client/Server Network
Server provides specific services for a specific purpose.
Users connected to the LAN through client computers
can access resources on any server on the network.
Centralized database illustrate the concept:
Client requests
Information.
Server responds
to request.
Servers tend to have faster processors, more RAM,
and more hard disk space. They perform the
processing for many clients. A slow server slows
all clients that use it.
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10. Peer-to-Peer (P2P) Network
Decentralized. There are no dedicated servers and no
single set of resources that all clients access.
Each host on a P2P network can act as a client, a
server or both.
Each host performs authentication
for other hosts that request its
resources.
Advantage: Loss of a single computer doesn’t mean that
all data is lost.
Disadvantages: Can be difficult to find a resource, and a user must remember many different passwords.
Individual P2P servers
grant/deny access.
P2P clients request
authentication.
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11. Centralized Networks
Rather than having to authenticate against each computer,
a user authenticates once and then can access all resources
on a LAN.
Assuming that their account has permissions of course!
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12. Centralized Networks Advantages of Centralized Networks:
Files can be stored and backed up centrally.
Servers can be located centrally for easy access.
Centralized administration
Fewer support personnel required.
Disadvantages of Centralized Networks:
Fewer points of failure
If a central resource like a file share goes offline,
many more users are inconvenienced.
Security
If you get a users password, you can access all
resources on the network, not just on one computer.
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13. Centralized Network Administration
Centralized networks allow an administrator to:
Deploy an application to a thousand desktop computers at the same time rather than visit each computer with the installation CD-ROM.
Standardize of modify the look and feel of all client
computers or make configuration changes centrally.
Have security updates automatically deployed to all
computers as they become available rather than having to visit each computer, check which updates are installed, and then finally install relevant updates.
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14. The OSI Reference Model
The OSI Reference Model is a complete conceptual
model for describing functions performed by network
hardware and software.
Each layer of the OSI model describes a particular
aspect of the network communication process.
Services provided at each layer interact directly with
those provided by the layers immediately above and/or
below.
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15. Layer 7 Application Layer Layer 6 Presentation Layer Layer 5 Layer 4
Initiates communication to use the network, such as starting a file transfer or displaying a Web page.
Application Layer
Layer 6
Translates data into formats such as text, graphics, audio and video. Also includes data compression and encryption.
Presentation Layer
Layer 5
Establishes a logical communication channel for data transfer between hosts.
Layer 4
Breaks data message into transmittable segments and ensures accurate and reliable transmission of data packets in the proper sequence between hosts.
Session Layer
Layer 3
Identifies the location of source and destination hosts and routes the best pathway between.
Transport Layer
Layer 2
Ensures that data transmitted on the transmission media has a destination on the local network.
Network Layer
Layer 1
Transmits data across the physical media as a stream of
binary numbers in the form of electrical signals, light pulses of radio waves.
Data Link Layer
Physical Layer
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16. Summary
A LAN is a type of network where two or more hosts are connected at high speed.
LANs are used to share a small number of resources with a large number of hosts.
P2P networks allow hosts to act as both client and server.
Client/server networks have resources centralized on servers which clients access.
The benefits of LANs is that they allow centralized administration, centralized applications and centralized file storage and backup.
The OSI Reference Model has seven layers, which can conceptually be used to represent how software and hardware interact with one another on a network.
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17. Discussion Questions What is the difference between a LAN and a WAN?
What are the differences between a client and a server?
What are the advantages of a client/server network model over a peer-to-peer network model?
What are the benefits of centralized administration of computers on a LAN?
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