Chapter 8: Network Connectivity

1
Chapter 8 Network Connectivity

• A Guide to Operating Systems Troubleshooting
  and Problem Solving

2
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

3
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

4
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

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Telephone and Computer Networks Compared
6
Reasons for a Network

• Networks were invented for three interrelated
  reasons
• To share resources
• To save money
• To increase productivity

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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
• Allows electronic conferencing

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Development of Network Operating Systems

• Novell NetWare was one of the first network
  operating systems
• 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

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Bus Topology
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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
• Backbones - segments that join main networks and
  typically run at 100Mbps or higher

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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)

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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
• 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
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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

• 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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Implementing a Transport Protocol in an Operating
System

• A transport protocol is interfaced with three
  elements through hooks in the operating system
  kernel
• network driver specification built into the
  operating system
• a NIC (Network Interface Card)
• a NIC (Network Interface Card) driver
• Microsoft uses Network Device Interface
  Specification (NDIS) and Windows-based NDIS
  drivers
• NetWare uses Open Datalink Interface (ODI) and
  ODI drivers

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Communications Protocols

• Internet Packet Exchange (IPX) was developed to
  enable a NetWare file server to communicate with
  its client workstations
• Transmission Control Protocol (TCP) and Internet
  Protocol (IP) are usually used together
• Two other important communication protocols are
• NetBios Extended User Interface (NetBEUI) for
  Microsoft networks
• Apple Talk for Macintosh networks

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Internet Packet Exchange (IPX)

• IPX - a protocol developed by Novell and modeled
  after the Xerox Network System (XNS)
• IPX is tailored for NetWare environments and can
  be routed
• IPX encapsulates data and transports it within a
  host transport protocol format
• Sequence Packet Exchange (SPX) provides
  connection-oriented communications
• IPX works with several specialized service and
  NetWare protocols

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NetBEUI NetBIOS

• NetBEUI - interfaces software with network
  services
• introduced as the main protocol for LAN Manager,
  the forerunner of Windows NT Server
• Network Basic Input/Output System (NetBIOS)
  -provides a naming service for computers on
  Microsoft networks
• NetBIOS should not be confused with a protocol

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More NetBEUI

• NetBEUI is designed to be used on networks of
  under 200 stations
• It is compatible with applications that use
  NetBIOS
• NetBEUI is not designed to carry routing
  information
• Advantages of NetBEUI
• can handle nearly limitless communication
  sessions
• Low use of memory resources
• Quick transport of information on small networks
• Strong error detection and recovery
• Relatively easy configuration in the host
  operating system

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NetBEUI Flooding All Networks Within a Large
Network Setup
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TCP/ IP

• TCP/ IP - one of the oldest communications
  protocols
• developed for long distance networking on ARPANET
• used on most medium-to-large-scale networks
• UNIX has always used TCP/ IP as its main network
  communications protocol
• NetWare version 5, Windows 2000 Server, and
  Windows 2000 Professional also have adopted TCP/
  IP

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TCP/ IP

• TCP/ IP is used to network IBM mainframe
  computers that run the Multiple Virtual Storage
  (MVS)
• Computers that run the Virtual Memory System
  (VMS) TCP/ IP are also compatible with most
  networking operating systems

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Functions of TCP

• Communications functions performed by TCP
• Establish the communication session between two
  computers
• Ensure that data transmissions are accurate
• Encapsulate, transmit, and receive the payload
  data
• Close the communication session between two
  computers

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Functions of IP

• IP performs the following complementary functions
  with TCP
• Handles packet addressing
• Handles packet routing
• Fragments packets as needed for transport across
  different types of networks
• Provides simple packet error detection in
  conjunction with the more thorough error
  detection provided by TCP
• IP addressing uses the dotted decimal notation
  that consists of four 8-bit binary numbers

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More TCP/ IP

• Subnet mask - uniquely identifies smaller
  networks or subnetworks
• limits how much network traffic goes to certain
  networks and implements network security
• Computers and devices that use IP addressing have
  two addresses
• a physical address
• an IP address
• Today, IP version 4 is in used on nearly all
  networks, but its 32-bit (r-octet) addressing
  capacity is a problem
• Growth of the Internet has created an address
  shortage
• IP version 6 or IP Next Generation is using
  128-bit addresses

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Using TCP/ IP Subnet Masks
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TCP/ IP Works With a Range of Associated Protocols

• Routing Information Protocol (RIP)
• Simple Mail Transfer Protocol (SMTP)
• File Transfer Protocol (FTP)
• Internet Control Message Protocol (ICMP)

• Hypertext Transfer Protocol (HTTP)
• Point-to-Point Protocol (PPP)
• Simple Network Management Protocol (SNMP)
• Telnet

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AppleTalk

• AppleTalk - used between Macintosh computers
  primarily as a peer-to-peer protocol
• communications between networked Macintosh
  computers without the need for a server
• Windows NT and NetWare support AppleTalk as a
  means of communication with Macintosh computers

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Peer-to-Peer Networking Using AppleTalk
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AppleTalk Essential Services

• Remote access to files over a network, network
  print services, and access to computers running
  MS-DOS or Windows
• AppleTalk Phase II - newer version designed for
  large networks

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Implementing Communications Protocols in an
Operating System

• There are two steps involved in setting up a
  communications protocol
• install the protocol software that is written for
  that operating system
• bind the protocol with the NIC (Network Interface
  Card)
• Binding enables the NIC to set a priority for
  which protocol to process first
• Protocol priority has a direct impact on how fast
  the computer and its NIC process communications

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Implementing Communications Protocols in UNIX

• UNIX has TCP/ IP networking support built in and
  these automatically run a network configuration
  program when you first boot with an installed NIC
• NIC device drivers are loaded in the kernel
• Supplies information about the network connection
• If TCP/ IP is not automatically configured use
  the ifconfig command
• found in the /etc or /sbin directories
• enables you to assign an IP address, turn on the
  network interface and assign a subnet mask

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Implementing Communications Protocols in Mac
Windows

• Mac OS uses a Control Panel to designate a port
  for network communications
• Turn on AppleTalk from the Chooser window
• Windows 3.1 and 3.11 protocols are set up through
  the Main program group
• Network protocol configuration is modified by
  clicking Change System Settings, new setup
• Windows 3.11, the network protocol configuration
  is modified from the Options menu
• Communications protocols are set up in Windows
  95/98 and Windows NT 4.0 through the Network icon
  in the Control Panel

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Installing IPX/ SPX in Windows 3.1
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Installing a Protocol in Windows 2000 Server
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Integrating Different Operating Systems on the
Same Network

• Select transport and communication protocols that
  are supported in all operating systems
• Ethernet is particularly well suited to a network
  that has different operating systems
• In situations where TCP/IP is not supported by
  all operating systems, multiple protocols can be
  configured such as a combination of AppleTalk,
  TCP/IP, and IPX/SPX

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Bridging

• Bridges - used to link networks that are close
  together
• Can also link remote networks
• Also used to segment a network into smaller
  networks
• Bridges operate in promiscuous mode
• examine the address of every frame that passes
  through them
• Bridges can be used for network security as
  firewalls

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Using a Bridge Filter to Direct Network A Frames
to Network D
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More About Bridging

• Bridges are protocol independent
• They are not designed to route packets from one
  network to another
• Bridges do not look at or process routing
  information, they are able to forward frames
  faster than other devices
• They can forward frames constructed by protocols

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Routing

• Routers are used to join networks, either locally
  or remotely
• Designed to look at routing information in
  packets before forwarding those packets
• Sensitive to different network protocols
• Direct and control network traffic more
  effectively
• Routers make excellent firewalls
• Maintain tables, called routing tables, that
  store information about local networks and
  information obtained from other routers

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Router Linking Different Types of Networks and
Protocols
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Local and Wide Area Networks

• Local area network (LAN) service area is
  relatively small, such as a network in an office
  are or one spread throughout a floor in a
  building
• Wide area network (WAN) offers networking
  services over a long distance such as between
  cities, states, or countries

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Using Operating Systems for Dial-Up Access

• Remote computers can access host computers and
  networks through dial-up networking and modem
  connections
• Windows NT Server offers a similar option called
  (RAS) remote access services
• Windows 95/ 98 and Windows NT all have a dial-up
  networking service

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Chapter Summary

• A network is a system of information resources
  and productivity tools
• Networks enable us to share information and
  resources over short and long distances
• They are designed in standardized topologies and
  use standardized communication means
• Modern computer operating systems can use a
  variety of network protocols

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Summary of Protocols
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Summary of Remote Communications Protocols