Why Use a LAN?

Information sharing

Having users access the same files, exchange information via

email, or use Internet

Ex: single purchase order database accessed by all users on the

LAN

Results in improved decision making Results in improved decision making

Resource sharing

Having hardware devices shared by all users

Printers, Internet connections

Having software packages shared by all users on a LAN

Results in reduced cost

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LAN Types

Dedicated server network

A server (computer) permanently assigned a specific

task

Most popular network type

90% of all LANs 90% of all LANs

Peer-to-peer network

No dedicated servers used

All computers act as both clients and servers

Cheaper than dedicated, but less capability

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Dedicated Server Networks

Requires one or more dedicated computers (servers)

Permanently assigned a specific task (Web server, e-

mail server, file server or print server)

Enable users to share files, printers, etc.,

May form a server farm (many servers part of a May form a server farm (many servers part of a

network)

Runs a server network operating system (NOS)

Windows NT, Windows Server, LINUX

Also requires a special communication software to

enable communications with client computers

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Types of Dedicated Servers

Common Types:

Web servers, e-mail servers, database servers

Others

File servers

Allows many users to share the same files on a common disk drive

Typically with restricted access

Print servers

Handle print requests

Could be a separate computer

Remote Access Servers

Enable users to dial in the LAN by phone (via modems)

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Components of a Local Area Network

SWITCH L2

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Local Area Network (LAN) in a large building

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Project 802 by IEEE: standards to enable communication among equipments:

Its a way of specifying functions of the physical layer and

the data link layer of major LAN protocols.

IEEE subdivided data link layer:

Logical Link Control (LLC), Media Access Control (MAC).

Wired LANs

- LLC provides one single data link control protocol for

all IEEE LANs.

- MAC provides different protocols for different LANs.

MAC defines specific access method for

each LAN:

- MAC provides different protocols for different LANs.- CSMA/CD

for Ethernet LAN,

- Token passing

for token ring,

-

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Wired LANs: Ethernet

Ethernet is the most widely used local area network protocol

Ethernet LAN is defined by IEEE 802.3 standard,

it uses 1-persistent CSMA/CD as the access method.

The MAC sublayer is responsible for the operation of

the CSMA/CD.

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Wired LANs: Standard Ethernet

Standard Ethernet 802.3 frame format

Each station has a unique 48-bit address imprinted on its Network Interface Card (NIC).

Example of an address in hexadecimal notation:

Frame length: The minimum frame length is 64 bytes; the maximum is 1518 bytes.

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Wired LANs: Standard Ethernet

Categories of Standard Ethernet

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10Base5 implementation

Wired LANs: Standard Ethernet

10Base2 implementation11

Wired LANs: Standard Ethernet

10Base-T implementation

10 Base T switch

10Base-F implementation

10 Base T switch

10 Base F switch 12

Summary of Standard Ethernet implementations

Wired LANs: Standard Ethernet

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Wired LANs: Ethernet evolution

Sharing bandwidth.

Collision domains in an unbridged

network and a bridged network.

Bridged Ethernet

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Wired LANs: Ethernet evolution

Switched Ethernet

Full-duplex switched Ethernet

CSMA/CD ?

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Wired LANs: Fast Ethernet

Fast Ethernet 802.3u

Upgrade the data rate to 100 Mbps.

Star topology only.

Compatible with standard Ethernet.

Keep: - the same frame format,

- the same minimum and maximum frame length.

Autonegotiation.

Fast Ethernet implementations

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Wired LANs: Fast Ethernet

Summary of Fast Ethernet implementations

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Wired LANs: Gigabit ETHERNET

Gigabit Ethernet 802.3z

Upgrade the data rate to 1 Gbps.

Star topology only.

Compatible with standard and fast Ethernet.

Keep: - the same frame format,

- the same minimum and maximum frame length.

Autonegotiation.

Gigabit Ethernet implementations

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Wired LANs: Gigabit ETHERNET

Summary of Gigabit Ethernet implementations

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Wired LANs: Ten-Gigabit ETHERNET

Ten- Gigabit Ethernet 802.3ae

Upgrade the data rate to 10 Gbps.

Star topology only.

Compatible with standard, fast, and Gigabit Ethernet.

Keep: - the same frame format,

- the same minimum and maximum frame length.

Summary of Ten-Gigabit Ethernet implementations

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