Introduction to Networking

1
Introduction to Networking

• Definitions and Terms

2
Chapter Objectives

• After completing this chapter you will
• Be able to differentiate between peer-to-peer and
  server-based networks.
• Be able to identify a network topology.
• Understand the different types of network
  cabling.
• Be able to explain the differences between
  various network access methods.
• Understand Ethernet issues.
• Identify OSI model layers.
• Be able to explain when a specific network
  protocol is used.
• Understand the difference between a MAC address
  and an IP address.

3
Chapter Objectives (cont.)

• After completing this chapter you will
• Be able to correctly apply IP addressing
  concepts.
• Understand the purpose of DHCP, WINS, and DNS.
• Be able to properly configure a NIC for network
  connectivity.
• Be able to use common network troubleshooting
  tools.
• Be able to access a network printer.
• Understand dial-up networking concepts and define
  commonly used network terms.

4
Chapter Objectives (cont.)

• After completing this chapter you will
• Be able to define and label the basic parts of a
  wireless network.
• Know that wireless networks operate at layers 1
  and 2 of the OSI model.
• Understand the difference between the two main
  types of wireless networks ad hoc and
  infrastructure.
• Know the three types of wireless NICs.
• Understand the difference between a BSS and an
  ESS.
• Be able to explain the purpose of an SSID and
  channel ID.
• Know the three non-overlapping channel IDs used
  by the 802.11b standard.

5
Chapter Objectives (cont.)

• After completing this chapter you will
• Understand the purpose of a wireless repeater.
• Be able to explain the basic differences between
  the antennas and explain the concept of
  attenuation.
• Know the difference between dBd and dBi.
• Know the purpose and importance of a site survey.
• Understand the difference between 802.11a,
  802.11b, and 802.11g.
• Understand the basics of wireless network
  security.

6
Networking Overview

• A network is two or more devices capable of
  communicating and sharing resources between them.
• Two types of networks are LAN and WAN
• LAN (Local Area Network) A group of devices
  sharing resources in a single area such as a room
  or a building.
• WAN (Wide Area Network) Two or more LANs
  communicating, often across large distances. The
  most famous WAN is the Internet.

7
Types of Local Area Networks

• Two types of LANs are Server-Based and
  Peer-to-Peer Network
• Server-Based Network A basic type of LAN
  wherein users login to a controlling computer,
  called a server and is more secure. The server
  contains information about who can connect to the
  network and to what shared resources. It also
  provides some of these resources. These networks
  normally consist of 10 or more computers.
• Peer-to-Peer Network One of two basic types of
  LANs wherein each computer user acts as a server.
  Each computer stores password and sharing
  information for its own resources. Usually has
  fewer than 10 computers.
• NOS (Network Operating System) Special
  operating system on a server containing utilities
  for managing users, resources, and security.

8
Types of Local Area Networks
Server-Based Network
Network Figure 1
9
Types of Local Area Networks
Peer-to Peer Network
Network Figure 2
10
Network Topologies

• Network Topology Maps of how the physical or
  logical paths of network devices connect. The
  three major topologies are star, ring, and bus.
• Star Topology Most common Ethernet network
  topology where each device connects to a central
  hub or switch.
• Hub A device used with the Universal Serial Bus
  or in a star network topology that allows
  multiple device connections.
• Switch In star networks, a Layer 2 central
  controlling device. A switch looks at each data
  frame as it comes through each port.
• Ring Topology Network that is physically wired
  like a star network but, logically in a ring
  passes control from one device to the next in a
  continuous fashion using a special data packet
  called a token. Used in Token Ring networks.
• Bus Topology Network wherein all devices
  connect to a single cable. If the cable fails,
  the network is down.
• Mesh Topology Network where all devices connect
  to each other by cabling to provide link
  redundancy for maximum fault tolerance. Most
  likely in WANs.

11
Network Topologies
Hub/Switch
Network Figure 3
12
Network Topologies
Star Topology
Network Figure 4
13
Network Topologies
Logical Ring Topology
Network Figure 5
14
Network Topologies
Bus Topology
Network Figure 6
15
Network Topologies
Network Topologies
Network Table 1
16
Network Cabling

• Cable is normally used as a medium for
  transporting network data. The most common types
  are twisted-pair and fiber-optic, although coax
  is still used in some old networks.
• Twisted-Pair Cable Network cable of eight
  copper wires twisted into four pairs to prevent
  crosstalk.
• UTP (Unshielded Twisted-Pair) Most common
  network cable that comes in different categories
  for different uses. Categories 3 (voice-grade),
  4, and 5 (data). It is unshielded and more
  susceptible to interference.
• STP (Shielded Twisted-Pair) Same as UTP cable,
  but with extra foil to prevent outside noise from
  interfering with data on the cable.
• Crosstalk Where signals from one wire interfere
  with the signal on an adjacent wire.
• Plenum cable is treated with Teflon or fire
  retardant materials to reduce the risk of fire.
  It produces less smoke and is less toxic when
  burning.

17
Network Cabling

• Fiber-Optic Cable An expensive network cabling
  made of plastic or glass fibers that carry data
  in the form of light pulses. Most often used to
  connect network devices such as switches together
  into a network backbone or for connecting
  networks together in a WAN. More secure and not
  affected by crosstalk or other interference like
  copper cable.
• Single-Mode A type of fiber-optic cabling that
  sends one light beam down the cable. Used for
  longer distance applications.
• Multi-Mode A type of fiber-optic cabling that
  allows multiple light signals to be sent along
  the same cable. Used for shorter distances.
• Coaxial Cable Type of copper network cabling
  used in older Ethernet networks as well as
  mainframe and minicomputer connections. Has a
  single, center wire conductor with an outer
  braided shield.

18
Network Cabling
UTP Cable
Network Figure 7
19
Network Cabling
Fiber-Optic Cable
Network Figure 11
20
Network Cabling
Coax Cable with Connector
Network Figure 12
21
Access Methods

• There are standard rules by which computers on a
  network must adhere to in order to communicate.
  These rules are known as a common access method.
• CSMA/CD (Carrier Sense Multiple Access/Collision
  Detect) A common access method used by
  Ethernet.
• Token Passing The common access method used by
  fiber and Token Ring networks.
• CSMA/CA (Carrier Sense Multiple Access/Collision
  Avoidance) A common access method used in
  wireless and Apple networks.
• Token Small data packet passed from one
  networked device to another in a ring topology.

22
Ethernet Issues and Concepts

• Two types of transmissions used in Ethernet
  networks
• Half Duplex A serial device setting that allows
  either the sending or the receiving device to
  send data, one device at a time. Data can travel
  both ways on a cable, but not at the same time.
• Full Duplex A serial device setting that allows
  the sending and receiving device to send data
  simultaneously. Data can travel both ways on a
  cable at the same time.

23
OSI Model

• OSI Model (Open Systems Interconnect) A
  standard for information transfer across a
  network that was developed by the International
  Standards Organization. The model has 7 layers.
• Physical Layer Layer 1 of the OSI model that
  defines how bits are sent and received across the
  network without regard to their structure.
• Data Link Layer Layer 2 of the OSI model that
  accurately transfers bits across the network by
  encapsulating (grouping) them into frames.
• Network Layer Layer 3 of the OSI model that
  coordinates data movement between two devices on
  separate networks.

24
OSI Model

• Transport Layer Layer 4 of the OSI model that
  determines details on how the data is sent,
  supervises the validity of the transmission, and
  defines protocol for structuring messages.
• Session Layer Layer 5 of the OSI model that
  manages communication and administrative
  functions between two network devices.
• Presentation Layer Layer 6 of the OSI model
  that defines how data is formatted, encoded,
  converted, and presented from the sender to the
  receiver, even though different computer language
  is used.
• Application Layer Layer 7 of the OSI model that
  defines how applications and the computer
  interact with a network, and negotiates services
  such as authentication, error recovery, and
  quality of service.

25
OSI Model

• ISP (Internet Service Provider) A vendor that
  provides connection to the Internet.
• Router A network device that determines the
  best path to send a packet. It works at OSI
  model Layer 3.

26
OSI Model
OSI Model Layers
Network Figure 13
27
OSI Model
OSI Peer Communication
Network Figure 14
28
OSI Model
OSI Model
Network Table 4
29
Networking Protocols

• Network Protocol Specifications that define the
  network data communication procedures to follow
  when sending and receiving data.
• TCP/IP (Transport Control Protocol / Internet
  Protocol) the most common network protocol used
  by most companies and home users as a standard
  protocol. Used to access the Internet.
• IPX/SPX (Internetwork Packet Exchange/Sequenced
  Packet Exchange) original protocol used for
  connecting to Novell networks. Now TCP/IP is the
  standard protocol used.
• NetBEUI (NetBIOS Enhanced User Interface) is a
  non-routable protocol used in simple networks
  commonly found on peer-to-peer networks.

30
Network Addressing

• Network devices have to be able to identify each
  other in order to communicate across a network.
  They do this through various network addressing
  schemes.
• MAC Address One of two types of addresses
  assigned to network adapters, used when two
  devices on same network communicate.
• IP Address A type of network adapter address
  used when multiple networks are linked. It is a
  32-bit binary number with groups of eight bits
  separated by a dot.
• Network Number Portion of an IP address that
  represents which network the computer is on.

31
Network Addressing

• Host Number Portion of an IP address that
  represents the specific network device.
• Broadcast Address IP address used to
  communicate with all devices on a particular
  network.
• Subnet Mask A number the computer uses to
  determine which part of an IP address represents
  the network and which portion represents the host.

32
Network Addressing
IP Addressing (Network Number and Host Number)
Network Figure 15
33
Network Addressing
IP Addressing (Two Network Example)
Network Figure 16
34
Network Addressing
IP Address Information
Network Table 5
35
Configuring Networking

• Some key terms to understand when configuring
  computers for networking are
• UNC (Universal Naming Convention) A standard
  way of naming computers and shared resources on a
  network. Used at the command prompt to obtain
  network shares.
• DHCP (Dynamic Host Configuration Protocol) A
  method to automatically assign IP addresses to
  network devices from a pool of IP addresses. A
  computer requests an address from another device
  running DHCP, usually a server, receives it, and
  joins the network.
• APIPA (Automatic Private IP Addressing) Assigns
  an IP address and mask to the computer when a
  DHCP server is not available.
• Default Gateway The IP address of the Layer 3
  device, such as a router, that is directly
  connected to its immediate network and acts as a
  doorway or director to other remote networks.

36
Configuring Networking

• DNS (Domain Name System) Server Application on
  a network server that translates Internet names
  (also known as Fully Qualified Domain Names or
  hostnames) into IP addresses.
• URL (Universal Resource Locator) A method of
  accessing Internet resources by using a simple,
  easily remembered name assigned to an IP address.
  An example of a URL is www.scottjonespub.com,
  which is much easier to remember than the IP
  address 167.160.239.173.
• WINS (Windows Internet Naming Service) Server
  Keeps track of IP addresses assigned to a
  specific computer name. A user can type in a
  computer name to connect and the server will
  translate it to the computers IP address.

37
Configuring Networking
Default Gateway
Network Figure 17
38
Network Troubleshooting

• IPCONFIG A command used with Windows 98, NT,
  and 2000 to see and modify the current IP
  settings.
• NSLOOKUP An NT Server and 2000 Server
  troubleshooting tool that displays network domain
  names and their associated IP addresses.
• Tracert A network troubleshooting command that
  displays the path a data packet takes through a
  network, thus allowing one to see where a fault
  occurs in larger networks.

39
Network Troubleshooting
Sample Network Configuration
Network Figure 18
40
Network Troubleshooting
WINIPCFG
Network Figure 19
41
Network Troubleshooting
IPCONFIG
Network Figure 20
42
Dial-up Networking

• There are several ways in which computers can
  connect to remote networks
• DUN (Dial-Up Networking) A remote computer that
  dials into the Internet or a corporation using a
  modem.
• VPN (Virtual Private Networking) A remote
  computer connecting to a remote network by
  tunneling over an intermediate network, such as
  the Internet or a LAN.
• PPP (Point-to-Point Protocol) A
  connection-oriented Layer 2 protocol that
  encapsulates data for transmission over remote
  networks. Very common for home users dialing in
  to the Internet.

43
Dial-up Networking
Dial-Up Networking and VPN
Network Figure 21
44
Dial-up Networking
Network Connections
Network - Table 7
45
Internet Software

• Once a connection is established to a remote
  network there are several program types that are
  useful for accessing data.
• Browser A program that views web pages across
  the Internet. The two most common are Internet
  Explorer and Netscape Navigator.
• Proxy Server Acts as an agent between an
  application and a real server for security
  purposes.
• SMTP (Simple Mail Transport Protocol) is a
  protocol used for sending and receiving email.
  Settings for configuring email can be obtained
  from the network administrator or the ISP being
  used to connect to the Internet.

46
Internet Security

• There are three major points to remember
• Keep service patches updated on a regular basis.
• The latest anti-virus software should be
  installed and constantly updated.
• If the computer connects to the internet, it
  should be connected behind a firewall.
• Cookie A special program written to collect
  information and store it on the hard drive. This
  will contain your preferences when you visit a
  website.
• Firewall Software or hardware that protects one
  or more computers from outside attacks.

47
Network Terminology

• Networking Terms and Acronyms To be Familiar
  With
• Backbone Bandwidth Baseband
• Broadband E-mail Fast Ethernet
• FDDI Frame FTP
• HTML HTTP Infrared
• Packet POP SNMP
• TCP Telnet UDP

48
Wireless Networks Overview

• Wireless Networks Transmit data over air using
  either infrared or radio frequencies. Wireless
  networks operate at layers 1 and 2 of the OSI
  model.

49
Wireless Networks Types

• There are two main types of wireless networks
• Ad hoc also known as peer-to-peer or IBSS
  (Independent Basic Service Set) An ad hoc
  wireless network is when at least two devices
  such as two computers have wireless NICs.
• Infrastructure Wireless network that connects
  multiple wireless network devices through an
  Access Point.
• Access Point is similar to a network hub and
  connects wireless network devices.
• There are three major types of wireless NICs PC
  Card, USB, and PCI.

50
Wireless Networks Types

• BSS (Basic Service Set) Configuration when
  multiple devices connect to an Access Point.
• ESS (Extended Service Set) The network design
  when multiple Access Points connect to the same
  main network.
• SSID (Service Set Identifier) - A set of 32
  alpha numeric characters used to differentiate
  between wireless networks.
• The channel ID (frequency) between the Access
  Point and the adapter must match for
  communication to occur.

51
Wireless Networks Types
802.11b Frequency Channels
Network Table 12
52
Wireless Network Security Overview

• Wireless networks by their nature are insecure.
• All transmissions over air occur in clear text
  making them easy to compromise.

53
Authentication and WEP

• Authentication is the process of determining that
  a network device or person has permission to
  enter the wireless network through the access
  point.
• Open Authentication Allows a wireless network
  device to send a frame to the access point with
  the senders identity (MAC address). It is used
  when no authentication is required.
• Shared Key Authentication Requires the use of a
  shared key to communicate.
• WEP (Wireless Equivalent Privacy) Encrypts data
  when shared key authentication is used.
• Encryption the process of converting data into
  an unreadable format.

54
Default Settings

• All wireless networks have default passwords and
  SSIDs. They should be changed immediately to
  prevent hackers from gaining access.
• SSID Broadcasting The access point periodically
  sends out a beacon frame that includes the SSID.

Default Access Point Passwords