Networking BASICS

1
Networking BASICS

• Network Media
• Unit 1
• Lesson 2

2
Objectives

• Explain how data transmissions are sent and
  received.
• List and describe the types of transmission
  media.
• Describe the functions of a network interface
  card.

3
Types of Networks

• There are two types of networks by which
  information is transmitted
• circuit switched networks
• packet switched networks

4
Circuit Switched Network

• There is a dedicated and direct physical
  connection between sender and receiver.
• No other transmissions can take place while the
  connection is active.
• Once the transmission is ended, other connections
  can be made with other devices.
• It is ideal for voice communications because
  there are no interruptions from other devices or
  delays.

5
Packet Switched Network

• This network requires data transmission be broken
  into smaller units called packets.
• Each packet is sent independently through the
  network.
• It is used for data transmission because data is
  not as time-sensitive as voice communication.
• It allows multiple devices to share one line or
  frequency.
• It facilitates error correction.

6
Signaling Techniques

• There are two ways that a signal is sent across a
  network medium
• baseband signaling
• broadband signaling

7
Baseband Signaling

• Sends one data signal across the network media
• Entire capacity of the media is used for the one
  data signal
• Signals are transmitted in a digital format
• Many devices can send and receive across the
  medium, but only one at a time

8
Baseband Signaling
9
Broadband Signaling

• Divides the cable into several different channels
• Signals are transmitted at different frequencies
  in an analog mode
• Allows many different signals to be sent
  simultaneously on a single cable
• Signal sent in only one direction
• Used for computer network data transmissions

10
Broadband Signaling
11
Factors Affecting Transmissions

• The flow of a signal down the network media can
  become distorted.
• Common types of distortions are attenuation and
  interference.

12
Attenuation

• Loss of signal power
• Measured by the decrease in decibels (db) over a
  specific distance

13
Interference

• Interference is caused when a strong external
  signal interferes with a signal.
• Radio frequency interference (RFI) -
  interference caused by broadcast signals from a
  radio or television transmitter.
• Electromagnetic interference (EMI) - motor or
  source of intense electrical activity creates an
  electromagnetic signal that interferes with a
  data signal.
• Near end crosstalk (NEXT) and Far end crosstalk
  (FEXT) - interference from another data signal
  being transmitted on adjacent wire.

14
Transmission Media

• Copper cables
• Fiber optic cables
• Wireless

15
Copper Cables

• Thin coaxial
• Shielded twisted pair (STP)
• Unshielded twisted pair (UTP)
• UTP rated by Category 1 - 6

16
Copper Cables
17
Copper Cables
18
Fiber Optic

• This cable uses a thin cylinder of glass to send
  light impulses.
• The cable consists of a strand of glass (core)
  surrounded by a glass tube (cladding).
• Single mode - one light source flashes a light
  down the cable.
• Multimode - supports many simultaneous light
  transmissions.

19
Fiber Optic
20
Wireless

• Transmission is sent and received through
  invisible waves
• Less expensive than copper or fiber optic lines.
• Allows the user to move freely around the office
  or campus and still remain connected to the
  network
• Fastest-growing segment of network media today

21
Wireless Transmissions

• Infrared transmits data using infrared (IR)
  light.
• IR shares many of the same properties as visible
  light .
• Radio frequency signals can be transmitted over
  radio waves similar to local radio station
  transmissions.
• The signal comes in at a lower power level and
  does not reach as far.

22
Network Interface Card

• The NIC serves as the connection between the
  personal computer and the network media.
• It connects to the computer on its base by
  plugging into an expansion slot of the computer.
• Another connection is accessible from the outside
  of the computer and has connections for the
  cables to plug into the network.

23
Network Interface Card

• Changes from parallel to serial transmission
• Creates packets
• Determines when to send
• Transmits packet

24
Network Interface Card
25
Summary

• Switching involves moving (switching) the signal
  from one wire or frequency to another. A circuit
  switched network creates a dedicated and direct
  physical connection between the sender and
  receiver. No other transmissions can take place
  while the connection is active, but once the
  transmission is ended, other connections can be
  made with other devices. Circuit switching is
  ideal for voice communications. Computer networks
  sending data use packet switched networks. Packet
  switching requires that the data transmission be
  broken into smaller units called packets. Each
  packet is then sent independently through the
  network to reach the destination.

26
Summary (continued)

• Baseband signaling sends one data signal across
  the network media. The entire capacity of the
  media is used for the one data signal that is
  transmitted in a digital format, which is made up
  of short impulses of off and on. The other type
  of signaling tech-nique is known as broadband
  signaling. Broadband transmis-sion divides the
  cable into several different channels. It does
  this because the signals are transmitted at
  different frequencies in an analog, or
  continuous, mode. Broadband transmission allows
  many different signals to be sent simultaneously
  on a single cable. Computer data networks use
  baseband signaling instead of broadband signaling.

27
Summary (continued)

• The flow of a signal down the network media can
  sometimes become distorted. The two common types
  of distortions are attenuation and interference.
  As the data travels, it meets resis-tance, which
  causes the signal to weaken gradually. This loss
  of signal power is known as attenuation.
  Interference or noise is caused when a strong
  external signal interferes with the signal being
  transmitted. Radio frequency interference (RFI)
  refers to interference caused by broadcast
  signals from a radio or television transmitter.
  Electromagnetic interference (EMI) may be caused
  by a variety of sources. The source of near end
  crosstalk (NEXT) interference is from another
  data signal being transmitted. Far end crosstalk
  (FEXT) is similar to NEXT except that the
  interference is measured at the far end of the
  wire.

28
Summary (continued)

• There are many different types of network media,
  yet they all can be classified into three major
  categories copper, fiber optic, and wireless.
  Thin coaxial cable is approximately one-quarter
  of an inch in diameter, has a single copper wire
  at its center, and is surrounded by a layer of
  insulation. Around the insulation is a braided
  copper mesh channel, and everything is covered by
  a thick outer shield of insulation. Twisted pair
  cable has become the standard today for copper
  cabling used in computer net-works, replacing
  thin coaxial cable. Twisted pair cable is two
  insulated copper wires that are twisted around
  each other. Each pair is then bundled together
  with other pairs in a jacket. There are two types
  of twisted pair cables. Shielded twisted pair
  (STP) cables have a foil shielding on the inside
  of the jacket, which reduces interference.
  Unshielded twisted pair (UTP) cables do not have
  any shielding.

29
Summary (continued)

• A fiber optic cable uses a very thin cylinder of
  glass, instead of copper, at its center. Fiber
  optic cables send light impulses instead of
  transmitting electrical signals. Wireless
  communica-tion uses no visible connection, such
  as a copper cable or fiber optic line, between
  the network devices. Instead, the transmis-sion
  is sent and received through invisible waves.
  Transmission signals can be sent by infrared
  light waves or radio frequency waves.

30
Summary (continued)

• When connecting a personal computer to the
  transmission media on a LAN, hardware known as a
  network interface card (NIC) is used. A NIC
  serves as the connection between the personal
  computer and the network media. The NIC connects
  to the computer on its base by plugging into one
  of the expansion slots of the computer. The other
  connection, found on the side of the NIC, is
  accessible from the outside of the computer and
  has connections for the cables to plug into the
  network (or an antenna for wireless
  transmissions). These connections depend on the
  type of network media being used.