Network Access and Transmission Methods

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Network Access and Transmission Methods

• Chapter 10

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Objectives

• In this chapter, you will learn to
• Recognize simple and complex physical topologies
  used in data networks
• Describe Ethernet and the CSMA/CD network access
  method
• Understand the different types of Ethernet access
  methods
• Describe the techniques used in the Token Ring,
  ATM, and FDDI network access methods
• Identify the main characteristics of network
  transmission methods, such as X.25, Frame Relay,
  T-Carriers, ISDN, DSL, cable, and SONET

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Bus
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Ring
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Star
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Hybrid Physical Topologies
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Hybrid Physical Topologies
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Mesh Topologies
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Mesh Topologies
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Network Access Methods
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Ethernet

• A network access method originally developed by
  Xerox in the 1970s and later improved by Xerox,
  Digital Equipment Corporation (DEC), and Intel.
• Can run on a variety of network media, including
  both wireline and wireless channels
• Uses packet switching

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Ethernet

• Baseband - a transmission form in which digital
  signals are sent through direct current (DC)
  pulses applied to the wire.
• Multiple Access - refers to the fact that
  Ethernet nodes can be connected to a network and
  can monitor and issue traffic.
• CSMA/CD - Rules for communication used by shared
  Ethernet networks.

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Ethernet
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Ethernet

• Ethernet Frames - each frame contains a 14-byte
  header and a 4-byte frame check sequence (FCS)
  field.
• 10BaseT - a physical layer standard for networks
  that use baseband transmission and twisted pair
  media and can achieve 10 Mbps throughput.

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Ethernet
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Ethernet
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Ethernet

• 10BaseF - a physical layer standard for networks
  that use baseband transmission.
• 100BaseT - uses baseband transmission and
  multimode fiber cabling and can achieve 100 Mbps
  throughput.
• 100BaseF - specifies a network capable of 100
  Mbps throughput that uses baseband transmission
  and fiber optic cabling.
• Switched Ethernet - enables multiple nodes to
  simultaneously transmit and receive data over
  different network segments.

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Ethernet
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Token Ring

• Transmits at either 4, 16, or 100 Mbps over STP
  or UTP.
• Uses the token-passing routine and a star-ring
  hybrid physical topology.
• High Speed Token Ring (HSTR) - can use either
  twisted pair or fiber cable as its transmission
  medium.

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FDDI

• A network access method whose standard was
  originally specified by ANSI in the mid-1980s and
  later refined by ISO.
• Uses a double ring of multimode or single mode
  fiber to transmit data speeds of up to 100 Mbps.

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FDDI
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ATM

• Asynchronous Transfer Mode (ATM) - a standard
  that describes both a network access method and a
  multiplexing technique.
• Cells - consist of 48 bytes of data plus a
  five-byte header for a 53-byte packet.
• Virtual circuits - logical connections between
  network nodes.

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ATM

• Quality of Service (QoS) - a standard that
  specifies that data will be delivered within a
  certain time period after its transmission.
• Compatibility - ATM cells can support multiple
  types of higher-layer protocols, including TCP/IP
  and IPX/SPX.

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Network Transmission Methods

• X.25 and Frame Relay - a set of protocols
  designed for long-distance data transmission and
  standardized by the ITU in the mid-1970s.
• Frame Relay - an updated, digital version of X.25
  that also relies on packet switching. It does
  not guarantee the delivery of data.

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Network Transmission Methods
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ISDN

• An international standard, established by the ITU
  for transmitting data over digital lines.
• All ISDN connections are based on two types of
  channels
• B Channels employ circuit-switching techniques
  to carry voice, video and other types of data
  over the ISDN connection.
• D Channels employ packet switching techniques
  to carry information about the call, such as
  session initiation and termination signals,
  caller identity, call forwarding, and conference
  calling signals.

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Basic Rate Interface
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Primary Rate Interface
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T-Carrier Services

• The general name for a group of transmission
  methods that includes T1s, fractional T1s, and
  T3s.
• T-carriers are examples of dedicated leased
  lines.
• They are also private lines.

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Types of T-Carriers

• Signal level - the T-carriers Physical layer
  electrical signaling characteristics as defined
  by ANSI standards in the early 1980s.
• T1 Circuit - can carry the equivalent of 672
  voice or data channels, giving a maximum data
  throughput of 44.736 Mbps.

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Types of T-Carriers
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T-Carrier Connectivity

• Transmission Media - T1 technology can use
  unshielded or shielded twisted-pair copper
  wiring.
• CSU/DSU (Channel Service Unit/Data Service Unit)
  - the connection point for a T-carrier line at
  the customers site.
• CSU provides termination monitoring.
• DSU converts the digital signals used by
  bridges, routers and multiplexers into the
  digital signal sent via the cabling.

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T-Carrier Connectivity
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Multiplexers
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Multiplexers
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DACS
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DSL

• Uses advanced data modulation techniques to
  achieve extraordinary throughput over regular
  phone lines.
• Downstream - data traveling from the
  telecommunications carriers end office.
• Upstream - data traveling from the customer to
  the carriers end office.
• Types of DSL
• Asymmetrical downstream throughput is usually
  much higher than upstream throughput.
• Symmetrical - provides equal capacity for data
  traveling both upstream and downstream.

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DSL
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DSL Connectivity
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DSL Connectivity
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Cable Modem Technology
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SONET and SDH
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SONET and SDH
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Summary

• Network Access and Transmission Methods
• Bus, Ring, Star
• Hybrid Physical Topologies
• Mesh Topologies

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Summary (cont.)

• Network Access Methods
• Ethernet
• Token Ring
• FDDI
• ATM

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Summary Slide (cont.)

• Network Transmission Methods
• ISDN
• Basic Rate Interface
• Primary Rate Interface
• T-Carrier Services
• Types of T-Carriers

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Summary Slide (cont.)

• Multiplexers
• DACS
• DSL
• DSL Connectivity
• Cable Modem Technology
• SONET and SDH