Network Transmission Equipment

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Network Transmission Equipment

• Chapter 4

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Learning Objectives

• Describe the purpose of LAN network transmission
  equipment
• NICs, repeaters, MAUs, hubs, bridges, routers,
  brouters, switches, and gateways
• Explain how LAN network equipment works

continued
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Learning Objectives

• Describe 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 Equipment

• NICs
• Repeaters
• MAUs
• Hubs
• Bridges

• Routers
• Brouters
• Switches
• Gateways

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NIC

• Enables network device to connect to network
• Network connection requirements
• Appropriate connector for network medium
• Transceiver
• Controller to support MAC sublayer of Data Link
  layer
• Protocol control firmware

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A Combination NIC
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Role of MAC Controller Unit

• Works 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 options
• Combined transport options make it easy to
  upgrade a network for high-speed communication
• Transmissions options
• Half-duplex transmissions
• Full-duplex transmissions

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FDDI NICs

• Connect 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 NICs

• Connect ATM switches or servers to an ATM network
  
• Available to desktop
• Relatively expensive

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Wireless NIC

• Modes
• 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 NICs

• Industry 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 NIC

• For 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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Repeater

• Amplifies 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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Repeaters

• Advantage
• Inexpensive way to extend a network
• Disadvantage
• Can 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 topology
• Move token and frames around the ring
• Amplify data signals
• Connect in a daisy-chained manner to expand token
  ring network
• Provide for orderly movement of data
• Shut down ports to malfunctioning nodes

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MAUs

• Passive 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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Hub

• Central 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 network
• Permit many computers to be connected on single
  or multiple LANs
• Provide multiprotocol services
• Consolidate network backbone
• Provide connections for different media types
• Enable centralized network management and design

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Types of Network Hubs

• Unmanaged hubs
• Dual-speed hubs
• Workgroup hubs
• Stackable hubs
• Chassis hubs

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Bridge

• Connects different LANs or LAN segments using the
  same access method
• Operates in promiscuous mode can look at frame
  addresses (unlike repeaters)
• Operates at MAC sublayer of OSI Data Link layer
• Protocol 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 Functions

• Learning
• Filtering
• Forwarding

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Cascade Bridging
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Advantages of Bridges

• Limit 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 Bridges

• Local bridge
• Connects networks in close proximity
• Can be used to segment a portion of a network to
  reduce heavy traffic problems
• Remote bridge
• Joins networks across the same city, between
  cities, and between states to create one network

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Bridge

• Token ring source-route bridge
• Incorporated into 802.5 token ring LAN
  specification
• Performs routing at OSI Network layer
• Spanning tree algorithm
• Ensures that frames are not transmitted in an
  endless loop
• Enables 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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Router

• Connects 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 Routing

• Static routing
• Controls routing decisions by network
  administrator through preset routing instructions
• Dynamic routing
• Constantly checks network configuration
• Automatically updates routing tables
• Makes decisions about how to route packets

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Routing Tables and Protocols

• Routing tables
• Contain addresses of other routers
• Routing protocols
• Routing Information Protocol (RIP)
• Communicates entire contents of routing tables to
  other routers
• Open Shortest Path First (OSPF) protocol
• Communicates information about immediate links to
  other nodes

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Advantages of OSPF Protocol

• Sends 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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Brouter

• Acts 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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Switch

• Links 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 Techniques

• Cut-through switching
• Store-and-forward switching (buffered switching)

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Gateway

• Enables communications between two different
  types of networked systems

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Gateways Are Used to

• Convert commonly used protocols to a specialized
  protocol
• Convert message formats
• Translate different addressing schemes
• Link a host computer to a LAN
• Provide terminal emulation
• Direct electronic mail to the right network
  destination
• Connect 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 medium
• Works at OSI Physical layer, switching from
  channel to channel using
• A single method for optical transmissions
  (wavelength division multiplexing or WDM), or
• One 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 Bank

• Large-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 Networks

• Private branch exchanges (PBXs)
• Private automatic exchanges (PAXs)
• Private automatic branch exchanges (PABXs)

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Telephone Modems

• Convert computers 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 Modems

• Types 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 Adapters

• Connect 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 Modems

• Digital 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 Routers

• Digital 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 Servers

• Connect 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 Routers

• Join 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 Summary

• Network transmission equipment used on LANs,
  WANs, or both
• Modems
• Bridges
• Gateways
• Channel banks
• Access servers