1 Network Transmission Equipment Chapter 4. 2 Learning Objectives Describe the purpose of LAN...

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Network Transmission Equipment

Chapter 4

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Learning ObjectivesDescribe the purpose of LAN network transmission equipment:

NICs, repeaters, MAUs, hubs, bridges, routers, brouters, switches, and gateways

Explain how LAN network equipment works

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Learning ObjectivesDescribe the purpose of WAN network equipment:

Multiplexers, channel banks, private telephone networks, types of modems, ISDN adapters, access servers, and routers

Explain how WAN network equipment works

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LAN Transmission EquipmentNICs

Repeaters

MAUs

Hubs

Bridges

Routers

Brouters

Switches

Gateways

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NICEnables network device to connect to networkNetwork connection requirements

Appropriate connector for network mediumTransceiverController to support MAC sublayer of Data Link layerProtocol control firmware

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A Combination NIC

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Role of MAC Controller UnitWorks with firmware to correctly encapsulate:

Source and destination address information

Data to be transported

CRC error control information

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Transport andTransmission Options

Transport optionsCombined transport options make it easy to upgrade a network for high-speed communication

Transmissions optionsHalf-duplex transmissions

Full-duplex transmissions

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FDDI NICsConnect host systems/file servers to FDDI network equipment using single attachment

Attach network equipment to FDDI cabling via dual attachment

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ATM NICsConnect ATM switches or servers to an ATM network

Available to desktop

Relatively expensive

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Wireless NICModes

Ad hoc peer-to-peer communication with another wireless NIC

Communication with an access point

Provide flexibility and convenience

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Buses and NICsIndustry Standard Architecture (ISA)

Extended Industry Standard Architecture (EISA)

Microchannel Architecture (MCA)

Peripheral Computer Interface (PCI)

SPARC Bus (SBUS)

NuBus

Universal Serial Bus (USB)

VESA local bus (VL-bus)

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Choosing a NICFor host computer, server, or workstation?Network media and network transport methods in use?Manufacturer?Computer or network equipment bus type?Operating system used by the computer?Use of half- or full-duplex communications?How does it attach to network (for special application)?

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RepeaterAmplifies and retimes a packet or cell-carrying signal so that it can be sent along all outgoing cable segments attached to that repeater

Filters out signal disturbance or noise

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Repeaters Are Used to…Extend cable segment

Increase number of nodes beyond limit of one segment

Sense network problem and shut down cable segment (partitioning)

Connect to components in other network devices

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Repeaters Are Used to…Connect segments that use different media

Extend backbone cable segments in LANs and WANs

Extend long, fiber-optic cable segments

Increase communications distance of T-carrier lines

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A Multiport Repeater

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RepeatersAdvantage

Inexpensive way to extend a network

DisadvantageCan create excessive amount of network traffic

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Multistation Access Unit (MAU)

Central hub that links token ring nodes into a topology that physically resembles a star but in which data signals are transferred in a logical ring pattern

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MAUs Are Used to…Connect workstations into a logical ring through physical star topologyMove token and frames around the ringAmplify data signalsConnect in a daisy-chained manner to expand token ring networkProvide for orderly movement of dataShut down ports to malfunctioning nodes

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MAUsPassive hub

Active hub

Patch cables and lobe cables

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Ring In and Ring Out Ports

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Token Ring MAU Specifications

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HubCentral network device used in star topology to join networks

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Hubs Are Used to…Provide a central unit from which to connect multiple nodes into one networkPermit many computers to be connected on single or multiple LANsProvide multiprotocol servicesConsolidate network backboneProvide connections for different media typesEnable centralized network management and design

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Types of Network HubsUnmanaged hubs

Dual-speed hubs

Workgroup hubs

Stackable hubs

Chassis hubs

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BridgeConnects different LANs or LAN segments using the same access methodOperates in promiscuous mode; can look at frame addresses (unlike repeaters)Operates at MAC sublayer of OSI Data Link layerProtocol independent; only look at MAC address

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Bridges Are Used to…Extend a LAN when maximum connection limit has been reached

Extend a LAN beyond the length limit

Segment LANs to reduce data traffic bottlenecks

Prevent unauthorized access to a LAN

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Bridged Network

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Bridge FunctionsLearning

Filtering

Forwarding

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Cascade Bridging

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Advantages of BridgesLimit traffic to certain network segments; enhance performance

Can use as a firewall to keep intruders out of a network

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Types of BridgesLocal bridge

Connects networks in close proximity

Can be used to segment a portion of a network to reduce heavy traffic problems

Remote bridgeJoins networks across the same city, between cities, and between states to create one network

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BridgeToken ring source-route bridge

Incorporated into 802.5 token ring LAN specificationPerforms routing at OSI Network layer

Spanning tree algorithmEnsures that frames are not transmitted in an endless loopEnables frames to be sent along most cost-effective network path

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Bridge Protocol Data Units (BPDUs) Frame Format

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RouterConnects networks having the same or different access methods and media

Forwards packets to networks by using decision-making process based on:

Routing table data

Discovery of most efficient routes

Preprogrammed information from network administrator

Connects LAN at Network layer of OSI model

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Routers Are Used to…Efficiently direct packets from one network to another, reducing excessive traffic

Join neighboring or distant networks

Connect dissimilar networks

Prevent network bottlenecks by isolating portions of a network

Secure portions of a network from intruders

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Static and Dynamic RoutingStatic routing

Controls routing decisions by network administrator through preset routing instructions

Dynamic routingConstantly checks network configuration

Automatically updates routing tables

Makes decisions about how to route packets

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Routing Tables and ProtocolsRouting tables

Contain addresses of other routers

Routing protocolsRouting Information Protocol (RIP)

Communicates entire contents of routing tables to other routers

Open Shortest Path First (OSPF) protocolCommunicates information about immediate links to other nodes

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Advantages of OSPF ProtocolSends only the portion of routing table that pertains to its most immediate router links

Packages routing information in more compact format that RIP

Only updated routing table information is shared among routers, rather than the entire routing table

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BrouterActs as a bridge or a router, depending on how it is set up to forward a given protocol

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Brouters Are Used to…Handle packets efficiently on a multiprotocol network that includes some protocols that can be routed and some that cannot

Isolate and direct network traffic to reduce congestion

Join networks

Secure a certain portion of a network by controlling who can access it

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SwitchLinks network segments

Forwards and filters frames between segments

Provides bridging capacity and the ability to increase bandwidth on existing networks

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Switching TechniquesCut-through switching

Store-and-forward switching (buffered switching)

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GatewayEnables communications between two different types of networked systems

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Gateways Are Used to…Convert commonly used protocols to a specialized protocolConvert message formatsTranslate different addressing schemesLink a host computer to a LANProvide terminal emulationDirect electronic mail to the right network destinationConnect networks with different architectures

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Gateway

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WAN Transmission Equipment

Designed to work over POTS and leased telephone lines (T-carrier and ISDN)

May be analog or digital

Either converts a signal for long-distance communications or creates multiple channels

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Examples of Basic WAN Transmission Equipment

Multiplexers

Channel banks

Private telephone networks

Telephone modems

ISDN adapters

Cable TV modems

DSL modems and routers

Access servers

Routers

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Multiplexer (MUX)Can receive multiple inputs and transmit them to a shared network mediumWorks at OSI Physical layer, switching from channel to channel using:

A single method for optical transmissions (wavelength division multiplexing or WDM), orOne of three electrical switching methods

Time division multiple access (TDMA)Frequency division multiple access (FDMA)Statistical multiple access

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Using Multiplexers

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Channel BankLarge-scale multiplexer that combines telecommunications channels in a centralized location

First used in voice applications, now handle voice, data, and video

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Private Telephone NetworksPrivate branch exchanges (PBXs)

Private automatic exchanges (PAXs)

Private automatic branch exchanges (PABXs)

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Telephone ModemsConvert computer’s outgoing digital signal to analog signal that can be transmitted over a telephone line

Also convert incoming analog signal to a digital signal the computer can understand

Attached internally or externally

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Telephone ModemsTypes of connectors (DB-25, DB-9, PS/2, universal serial bus or USB)

Modem data transfer rate measured by baud rate or bits per second (bps)

Synchronous or asynchronous communication format

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ISDN AdaptersConnect a computer or fax to an ISDN line

Terminal adapter (TA) converts digital signal to a protocol that can be sent over a digital telephone line

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Cable TV ModemsDigital modem devices designed for use with cable TV system, providing high-speed data transfer

Share bandwidth with others, but dynamically allocate unused cable bandwidth

Either internal or external

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DSL Modems and RoutersDigital Subscriber Line (DSL)

Uses advanced modulation technologies on existing telecommunications networks for high-speed networking between subscriber and telco

Communication speeds up to 60 Mbps

Dedicated to single user; employs full bandwidth of the line

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Connecting to DSL

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Access ServersConnect synchronous and asynchronous devices to a network, providing routing for both types of communications

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Using an Access Server

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Remote RoutersJoin networks in WANs over long distances

Connect ATM, ISDN, frame relay, high-speed serial, and X.25 networks

Can support multiple protocols

Can be set up as firewalls

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Chapter SummaryNetwork transmission equipment used on LANs, WANs, or both

Modems

Bridges

Gateways

Channel banks

Access servers