Local Area Networks

Local Area Networks

A data communication system that allows a number of independent devices to communicate directly with each other in a limited geographic area.

Four Architectures

• Ethernet• Token Bus• Token Ring• Fiber Distributed Data Interface (FDDI)

*The first 3 are IEEE standard while FDDI is an ANSI standard

OSI Model and Project 802

LLC – logical link control- non architecture specific, common to all LANs- contains the logical addresses, control information and data

MAC – medium access control- resolves the contention for the shared media- contains the synchronization, flag, flow and error control- contains the physical address of the next station

Project 802

PDU Control Field

ETHERNET

Access MechanismCSMA/CD Carrier Sense Multiple Access/Collision Detection

LLC

MAC Frame

PDU length = 46 to 1500 bytes

Thick Ethernet / Thicknet

Transceiver

Connection

Ethernet Segments

Thin Ethernet/Thinnet/Cheapnet/Cheapernet

Max length (hub to station) – 100m

StarLAN

Up to 10 stations in a chain

Fast Ethernet

IEEE 802.3u

Why do we need to increase the speed of Ethernet LAN

Many companies now use Internet technologies to build private corporate intranets, for accessing critical data.

Multimedia client/server applications.

Introduction of more sophisticated operating system and applications, faster processors and greater disk and memory capacities.

Fast Ethernet• Data rate: 100 Mbps

• Increases the speed limit of the highway by orders of magnitude from 10 Mbps to 100 Mbps to 1000 Mbps (Gigabit Ethernet)– Reduces the amount of time it takes to transmit 1

bit by a factor of 10.

• Employs a star topology at the physical layer and supports twisted pair and fiber-optic cable.

Fast Ethernet• 3 different media specifications

– 100BASE-TX– 100BASE-T4– 100BASE-FX

The first 2 use twisted pair cable and the third uses fiber optic cable.

All 3 are designed to interoperate with one another

100BASE-TX• Transmits and receives data over two pairs of Cat 5 UTP

cable• Uses full duplex signaling system• Distance between station and hub is 100m• Networks based on this standard must be Cat-5

compliant, including wire, connectors, patch panels

1 pair for transmission1 pair for reception2 pairs are extra wires that can be used for voice

communication or reserved for further network enhancements*

100BASE-T4• Uses half-duplex signaling system to

transmit and receive data over 4 pairs of Cat 3, 4, 5 UTP cable.

• 1 pair for transmitting data • 1 pair for receiving data and collision detection• 2 pairs are used for either transmitting or

receiving *

100BASE-TX vs. 100BASE-T4 ?

100BASE-FX• Uses 2 strands of 62.5/125 micron multimode fiber

optic cable– 1 strand for transmission– 1 strand for reception

• Distance between station and hub is less than 2000m

• Signaling system is the same as100BASE TX

Gigabit Ethernet

Why do we need 1000Mbps technology?

Integration of faster computer systems

Migration of Fast Ethernet from backbone to the desktop

Deployment of multimedia applications

Gigabit Ethernet

Used as the backbone in many enterprise networks.

Alleviates congestion at server level or at interswitch connections. *

1000 Mbps - 1 billion bits per second IEEE 802.3z - Gigabit Ethernet over fiberIEEE 802.3ab - Gigabit Ethernet over copper

Gigabit Ethernet – over fiber– 1000BASE-SX (short wavelength fiber)

• 62.5 micron multimode fiber Max distance: 220-275 m• 50 micron multimode fiber Max distance: 500-550 m

– 1000BASE-LX (long wavelength fiber) • 62.5 micron multimode fiber, Max distance: 550 m• 50 micron multimode fiber, Max distance: 550 m• 9 micron single-mode fiber, Max distance: 5,000m (5km)

– 1000BASE-CX (short haul copper)• initial standard for Gigabit Ethernet connections over

Shielded single twisted-pair cable• Max distance: 25m

Gigabit Ethernet- over copper

• IEEE 802.3ab - Gigabit Ethernet over copper

– 1000BASE-T, running over Cat 5 cable at a distance up to 100 m.

More info about thet typeshttp://en.wikipedia.org/wiki/Gigabit_Ethernet