Transcript Chapter 12 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
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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
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
LLC – logical link control
- non architecture specific, common to all LANs
- contains the logical addresses, control information and data
Project 802
PDU Control Field
ETHERNET
Access Mechanism
CSMA/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
Introduction of more sophisticated operating system
and applications, faster processors and greater disk
and memory capacities.
Many companies now use Internet technologies
to build private corporate intranets, for
accessing critical data.
Multimedia client/server applications.
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 transmission
1 pair for reception
2 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?
Deployment of multimedia applications
Integration of faster computer systems
Migration of Fast Ethernet from
backbone to the desktop
Gigabit Ethernet
1000 Mbps - 1 billion bits per second
IEEE 802.3z - Gigabit Ethernet over fiber
IEEE 802.3ab - Gigabit Ethernet over copper
Used as the backbone in many enterprise networks.
Alleviates congestion at server level or at interswitch
connections. *
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 types
http://en.wikipedia.org/wiki/Gigabit_Ethernet