Download Applied Data Communications 2e

Chapter 6
Local Area Network Hardware
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LAN Technology Architecture
Network Interface Cards
Wiring Center
LAN Switches
Media
LAN Technology Architecture
• Shared-media LAN
• Switched LAN
Shared- Media LAN
• Sharing available bandwidth among all
devices
• 100BaseT, 100VG-Any-LAN, isochronous
Ethernet
Switched LAN
• Dedicated (guaranteed) bandwidth to switch
connected devices (point-to-point)
• Limited number of simultaneous point-topoint connections
• Replace the media-sharing LAN for more
bandwidth
Full-Duplex Network
Architectures
• Special type of switched LAN
• Full-duplex Ethernet, full-duplex token ring,
full-duplex FDDI
• Full-duplex Ethernet NICs, full-duplex NIC
drivers, and full-duplex Ethernet switches
Network Interface Cards (NICs)
Functions
• Physical link between devices
• Pass data between devices
• Determine the network architecture and
protocol
NICs - Technology Analysis
• Bus Type
– ISA, EISA, MCA, NuBus (Apple), PCI, PCMCIA, Sbus (Sun)
– Internal/external or external interface to parallel port
• Data transfer technique
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Bus-mastering DMA (direct memory access)
DMA(direct memory access)
Shared memory
Program I/O
Media interfaces (cables & connectors)
Network drivers
Management tools
Other hardware requirements
– On-board processor capabilities
– On-board memory
– System memory requirements
Bus Types
• Industry Standard Architecture (ISA): 8-bit or 16bit
• Microchannel Architecture (MCA): 32-bit
• Extended Industry Standard Architecture (EISA):
8-bit, 16-bit, 32-bit
• Local bus
– Video Electronics Standards Association (VESA local
bus or VL-Bus)
– Peripheral Component Interconnect (PCI local bus)
• Advanced graphic port by Intel
NICs - Trends
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Dual-speed cards: 10/100 Mbps
Integrated or on-board NICs
Multiport NICs
On-NIC virus protection and security
Integrated repeater modules (up to seven
devices)
• Full-duplex mode
• Performance improvement
NIC Drivers
• Functions: communication between NIC
and PC’s operating system
• Types:
– Monolithic drivers
– Multiprotocol network interface card drivers
• NDIS (network driver interface specification) by
Microsoft & 3Com
• ODI (open data-link interface) by Novell & Apple
– PCMCIA (PC Card or CardBus) drivers: card
and socket services (CSS)
PCMCIA
• Personal Computer Memory Card Interface
Association
• People Can’t Master Computer Industry
Acronyms
Wiring Center
• For Shared-media LAN
• Types
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Stand-along hubs
Stackable hubs
Multistation access units
Enterprise hubs
Stand-along Hubs
• Repeaters
– Retiming & regenerating digital signals
– Linking devices or LAN segments of similar
network architecture
• Hubs
– Subset of repeaters
– Connect single devices to its ports
– Concentrator or intelligent concentrator
Stackable Hubs
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Cascading ports for hubs
Specialized hub-to-hub cables
Expandability and manageability
Stackability ranging from 4 to 20
Multistation Access Units
• MAU: token ring hub
• Shielded twisted pair with Type 1
connectors
• Eight ports with additional ports: RI (ring
in) & RO (ring out) for cascading
• Active-management MAUs with identifying
and removing malfunctioning token ring
adapters
Enterprise Hubs
• Modular concentrators or network in a box
• Modular design and chassis-based architecture
• Hot-swappable: inserting and removing module
with power on
• Types of modules
– Ethernet, token ring, & FDDI port modules
– Management modules: security, encryption,
authorization modules
– Internetworking modules: router & bridge modules
– Multiple power supplies for redundant power
• Media: UTP, STP, thick or thin coax, &
fiber
Hub Management
• Software
– Local hub management software
– Enterprise network management software: HP’s
Open View, IBM’s NetView, Sun’s SunNet
Manager, Novell’s NMS
• Standard protocol
– Simple network management protocol (SNMP)
– Management information bases (MIB)
– Remote monitoring (RMON) MIB
Wiring Center Analysis
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Expendability
Reliability
Network architecture
Media
Internetworking: WAN, LAN, different
types
• Management
Wiring Center Management
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Operating system
Faults
Alarms
Statistics
Security
Remote
SNMP
LAN Switches: Architectures
• Stand-alone switches or slide-in modules
for enterprise switches:
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Ethernet switches
Token ring switches
FDDI switches
Fast Ethernet switches
• Super-Switches or Mega-Switches support
– Multiple different LAN
– ATM
– WAN
LAN Switch Methods
• Cut-through switches
– Fast
– No error checking
– Retransmitting
• Store-and-forward switches
– Slow
– Error checking
• Error-free cut-through switches
– Error checking
– Switch between cut-through & store-andforward depend on line condition
Switch Management
• Flow control
– Buffers
– Backpressure: false collision detection signal
• Monitoring
– Port mirroring
– Roving port mirroring
– Simultaneous RMON view using a shared
memory multigigabit bus
LAN Switch Analysis
• Switching methods: cut through, stored and
forward, error free stored and forward
• Network architecture: Ethernet, token ring,
FDDI, etc
• Port configuration and connection: single
device or multiple devices
• Full-duplex
• Internetworking: routing or bridge or both
• Management: SNMP
ATM for LAN
• IP over ATM
– TCP/IP protocol stack to employ ATM services
• LAN emulation
– A translation layer to use ATM services
LAN Media Alternatives
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Not twisted pair
Unshielded twisted pair
Shielded twisted pair
Coaxial cable
Fiber
Microwave radio
Satellite
Infrared
Not Twisted Pair: Phone Wire
• Four-conductor station wire (RYGB)
– Not for data transmission
• Flat gray modular wire or gray satin or
silver satin
– Data over short distance
Unshielded Twisted Pair
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22, 24, 26 American wire gauge(AWG)
Twisted pair or unshielded twisted pair (UTP)
Electrical noise & other interference
Electrical Industries
Association/Telecommunications Industries
Association (EIA/TIA): 5 grades (Cat 3 & Cat 5:
data grade)
– Attenuation
– Near-end crosstalk (NExT)
• Category 6
– Foil-twisted pair cable
– Data rate: 600 MHz
UTP Installation Mistakes
• Untwisting more than max 13 mm to wall
plates or punch-down block
• Exceed maxi bend radius (increase cross
talk)
• Tight wires too tight (cross talk)
Shielded Twisted Pair
• Pros:
– Less interference
– Faster speed
• Cons:
– More expensive
– Physically larger and difficult to connect to a
terminating block
Coaxial Cable
• Pros:
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Large bandwidth (400 - 600 MHz)
High capacity
Less interference
Good for noise environment
• Cons:
– Tapped easy (security problem)
– Bulky to install
Fiber - I
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Single mode: more expensive and capacity
Multimode graded index: medium expensive and capacity
Multimode or multimode step index: less expensive and capacity
Inexpensive plastic or copper
Expensive glass
• Pros:
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High bandwidth
No interference
No crosstalk
Small physical size and light weight
Very secure
• Cons:
– Repeater for long distance
– Expansive
Fiber - II
• Standard
– Synchronous optical network (SONET) in US
– Synchronous digital hierarchy (SDH) in Europe
• Main cable - TAT-8
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6 fiber optic
2 pairs for voice, video, and data
1 pairs for backup
Regenerator every 43 miles
Microwave Radio - I
• Characteristics
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Long distance
4-28 gHz frequency range
Straight line transmission
20-30 miles between transmission towers
Radio license by FCC
Microwave Radio - II
• Pros:
– Analog or digital signals
– For voice, data and television signals
– Long distance
• Cons:
– Interference by heavy rain
– Straight line transmission
– Security
• Vendors
– Motorola
– Rockwell Communication Systems
Satellite
• Characteristics:
– Microwave radio transmission
– Uplink and downlink
– Three satellites for the earth
• Pros:
– Analog or digital signals
– For voice, data and television signals
– Long distance
• Cons:
– Security and encryption
– Propagation delay
Infrared
• Light waves
• Line of sight
• Wireless communication between nearby
equipment
Circuit Ownership
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Private circuits
Leased circuits
Bypass
Switched (dial-up) circuits
Selection criteria
– Cost, speed, availability, reliability,
maintenance, users’ requirements
Circuit Identification
• Blue prints and document circuit and
equipment
• Circuit number to each circuit for
identification
Assignment
• Review chapters 5-6
• Read chapter 7