Lecture 8: Network Connectivity

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Lecture 8 Network Connectivity
Lecture 8 1st of 2 lectures on Chapter 8

• CPS 330

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Chapter Objectives

• Explain basic networking theory such as network
  topologies, packaging data to transport, and how
  devices connect to a network
• Describe network transport and communication
  protocols and determine which protocols are used
  in specific computer operating systems
• Explain how bridging and routing are used on
  networks
• Explain LANs and WANs
• Describe how network and workstation operating
  systems are used for remote networking

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Networks and Operating Systems Theory

• Centralized VS. Distributed Systems
• Key role of Networks in the development of modern
  operating systems
• Reflected in new management paradigms Business
  Process Reengineering

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Basic Networking Theory

• A network is composed of communications media,
  that is used to link
• computers
• printers
• disk storage
• CD-ROM arrays
• network communications equipment
• Claude Shannon on Communications Theory

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Basic Networking Theory

• Client operating system - can run applications
  locally and communicate with other computers on a
  network
• Workstation - computer connected to a network
  that can also run programs and access files
  locally
• Terminal - device that has a keyboard but no CPU.
  It is used to access and run programs on a
  server
• Networking operating system (NOS) - enables
  coordination of network activities
• Server - enables client workstations to access
  shared resources
• Hierarchical Network - network with a centralized
  server
• Client Server Network-eliminates cycle stealing
  for data distribution functions

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Telephone and Computer Networks Compared
Line Switching Vs. Packet Switching
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Reasons for a Network

• Networks were invented for three interrelated
  reasons
• To share resources
• To save money
• To increase productivity
• Dealers of Lightning Xerox Parc and the Dawn of
  the Computer Age

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Sharing Resources in an Office
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Steps to Sharing - Sneakernet

• Sneakernet - requires several time-consuming
  steps
• Format a floppy disk
• Copy a data file to the disk
• Walk to another persons desk, which is perhaps
  on another floor or in another building
• Take time for conversation with the other person
  while delivering the disk
• Walk back and possibly have more conversations
  with other employees along the way

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Networks Increase Productivity

• No need to hire an extra person to transport
  files and printouts
• Allows electronic mail (e-mail)
• Allows electronic commerce
• B2B (Business to Business Transactions and
  Partnerships)
• Allows electronic conferencing

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Development of Network Operating Systems

• Novell NetWare was one of the first network
  operating systems
• NT vs. Netware
• Client Server vs. Active Directory
• Windows 3.1 was first Windows-based operating
  system with network capabilities
• Windows for Workgroups added peer-to-peer
  networking, expanded workgroup capabilities, and
  provided more support
• Windows 95 expanded peer-to-peer networking and
  has the ability to connect to more kinds of
  networks
• Windows 98 adds the ability to connect to very
  high-speed networks

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Windows NT Operating System

• There are two versions of Windows NT
• Windows NT Workstation
• Windows NT Server
• There are several other network operating
  systems
• UNIX
• Banyan Vines
• Pathworks
• LAN Manager

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The Basics of Network Topologies

• Topology - the physical and logical design of a
  network
• Bus topology - connects all workstations to a
  single networking cable
• Each ending point has a terminator to keep the
  data signal from reflecting
• Ring Topology - a closed loop which connects all
  devices in a complete circle
• Star topology - each device connects to a central
  point

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Networking Hubs

• Hub - a device that connects multiple components
  of a network
• Passive hubs - pass the signal onto a segment
  without modifying it. The signal grows weaker
  each time it goes through the hub to the next
  segment
• Active hubs - amplify the signal to its original
  strength each time it goes through the hub
• Fiber Terminated
• Managed Hubs-able to collect communications
  statistics
• Non-Managed-cheap and dumb

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Bus Topology
Bus Topology Early Ethernet, Thicknet, Thinnet,
and Vampyre Taps
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Ring Topology
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Star Topology
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Packets, Frames, Cells

• Each data unit is called a packet, frame, or cell
• Packet - a data unit sent over a network that
  contains source and destination, routing,
  control, and error detection information. The
  routing information can be read by specialized
  devices that are able to forward packets to
  specific networks.
• Frame - a data unit sent over a network that
  contains source control, destination control, and
  error detection information
• Cell - a data unit designed for high-speed
  communications it has a control header and a
  fixed-length payload

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Basic Packet and Cell Format
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More About Packets, Frames and Cells

• Payload - the portion of a frame, packet, or cell
  that contains the actual data
• Protocol - a set of formatting guidelines for
  network communications so that the information
  can be accurately decoded at the receiving end
• Layered
• Backbones - segments that join main networks and
  typically run at 100Mbps or higher
• ATM
• Gibabit Ethernet

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Connecting to a Network

• Computers and internetworking devices connect to
  a network through a network interface card (NIC)
• The NIC is equipped with a connector that enables
  it to attach to the network communications cable
• Each NIC has a unique hexadecimal address that
  identifies it to the network
• A NIC is several devices built into one card
  (transmitter, receiver, connection interface)
• RJ-45 connectors, BNC connectors
• Ethernet nics vs. token ring nics
• NIC speed variability--10mbps, 100mbps, 10-100

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Devices on a Network
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Networking Protocols

• Coordinate transport of packets and frames among
  network devices
• Encapsulate data and communication control
  information
• Accomplish a specific functions, such as enabling
  the destination computer to tell the source
  computer to slow its transmitting speed
• Enable communications over a long distance
  network, such as the Internet
• Enable remote users to dial into network

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Transport Protocols

• Ethernet - a protocol that uses CSMA/ CD
  communications to coordinate frame and packet
  transmissions on a bus/ star network
• Token ring - a protocol that uses a ring topology
  and token passing as a way to coordinate network
  transport
• Both protocols are defined by the Institute of
  Electrical Engineers (IEEE)

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Ethernet

• Only one station on the network transmits at any
  given moment
• The transmission control method used is Carrier
  Sense Multiple Access with Collision Detection
  (CSMA/ CD)
• When the detected carrier signal is twice the
  strength of a normal signal, it indicates at
  least two network stations have transmitted at
  the same time
• Switches as a tool for separating a network
  suffering from saturation
• Two Varieties of Ethernet Protocol Communication
• IEEE802.3 standard frames
• Ethernet II uses slightly different frame format

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More About Ethernet

• Networks that use Ethernet are designed in a bus
  or star topology
• Ethernet was 10Mbps but newer Ethernet standards
  include 100 Mbps and 1 Gbps version that are
  called Fast Ethernet and Gigabit Ethernet
• All versions of Ethernet are compatible with most
  popular network operating systems

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Station with the Token in Token Ring
Pluses and Minuses of Token Ring Performance!
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Token Ring

• Token ring networks use the ring topology
• Only one network station transmits at a time
• The sequence of frame and packet transmission is
  controlled by the use of a specialized frame,
  called a token
• Only the station that has captured the token can
  transmit

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More About Token Ring and Token vs. Ethernet,
again!

• First station becomes the active monitor, all
  other stations are standby monitors
• The active monitor is charged with assessing
  transmissions to make sure a token frame exists
• Older token ring networks transmit at 4 Mbps and
  newer networks transmit at 16 Mbps
• IBM has recently developed 100 Mbps fast token
  ring topology
• Token ring is compatible with the same mainstream
  network operating systems as Ethernet

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Summary

• In this lecture, we reviewed some basics of
  network functionality!

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Posting Topics

• Research Xerox PARC what contributions are they
  credited with in the computer industry? What do
  You think is their most important contribution?
• How important is networking technology in causing
  the business world to redefine its vision of
  itself? Give concrete examples.
• Research Active Directory Services. Why is this
  considered an important technology?

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End