1. Introduction To Networking
Module 7 Part 1
Introduction To Networking

2. Objectives Understand the history of data communications
Describe the basic components of a network
Explain the methods of data transmission, including types of signals, modulation, and choices among transmission modes
Differentiate among the various kinds of communications links and appreciate the need for protocols

3. Data Communications Systems
Computer systems that transmit data over communications lines such as telephone lines or cables
History
Centralized data processing in early days
Distributed data processing began in late 1960s
Networks of personal computers began in 1980s

4. Centralized Data Processing
Places all hardware, software, and processing in one location
Very inconvenient and inefficient
Input data had to be physically transported to computer
Processed material had to be delivered to users

5. Distributed Data Processing
Uses computers that are at a distance from central computer
Local computers had access to central computers
Some processing done on local computers, some on central computers

6. Network
A group of two or more computer system that are linked together to exchange data and share resources over communication lines
Uses communications equipment to connect two or more computers and resources
Distributed data processing systems are networks
Local area network (LAN) designed to share data and resources among several users in office or building

7. Putting Together a Network
modems
routers
switches
(NIC) Network
Interface Cards
computers
Basic Components
Sending device
Communications link
Receiving device

8. Network Fundamentals Node Network Interface Card(NIC)
Any workstation or peripheral that is connected to network server, computer, peripheral devices, such as printer
Network Interface Card(NIC)
expansion boards that fit into a computer’s expansion slot.
Provide electronic connection between a computer and the network.

9. Network Fundamentals Routers Switches
Can determine the best path to route data
If traffic is clogged on one path, the router will determine an alternative path
Switches
Perform same function as router
However, it is simpler and faster
mechanism than a router

10. Digital and Analog Transmission
Digital transmission
Analog transmission
Modem

11. Digital Transmission Sends data as distinct pulses, either on or off
Similar to how data travels through computer

12. Analog Transmission Continuous electrical signal in the form of a wave
Called carrier wave
Many communications media already in place for analog (voice) transmission
Phone lines are most common
Digital signal from computer must be converted to analog form to be transmitted over analog lines

13. Converting Digital to Analog
Carrier wave can be altered
Amplitude (height) of wave
Frequency (number of times a wave repeats during a cycle) of wave
Conversion from digital to analog called modulation
Conversion from analog to digital called demodulation

14. Converting Digital to Analog
analog signal
Continuous electrical wave
digital signal
Distinct pulses that represent bits grouped together into bytes

15. Modem Short for modulator/demodulator
Internal modem -resides on an expansion board that plugs into a computer
Short for modulator/demodulator
Converts digital signal to analog and vice versa
Modulate  convert from digital to analog
Demodulate convert from analog to digital
Speeds up to 56,000 bps (56K)
ADSL modem
PC Card modem

16. Types of Modems External modem separate from computer
Internal modem inserted into computer
Standard on most computers today
PC Card modem slides into slot on laptop
Roughly credit card size
Cable connects modem to standard phone jack

17. Modem Data Speeds Measured in bits per second (bps)
Early modems transmitted at 300 bps
Fastest current modems transmit at 56,000 bps
Federal Communications Commission (FCC) restrictions prohibit actual speeds faster than 53,000 bps
Actual speed depends on line conditions and other variables

18. Other Communications Devices
ISDN
DSL
Cable modems
Cellular modems

19. Integrated Systems Digital Network (ISDN)
Special type of telephone circuit
Can move data at 128,000 bps
Includes two phone lines, so you can talk on the phone while online
Drawbacks
Expensive, especially at installation
Not available in all areas

20. Digital Subscriber Line (DSL)
Advantages of DSL:
Can leave your Internet connection open and still use the phone line for voice calls.
The speed is much higher than a regular modem
DSL doesn't necessarily require new wiring; it can use the phone line you already have.
The company that offers DSL will usually provide the modem as part of the installation.

21. Digital Subscriber Line (DSL)
Drawbacks
A DSL connection works better when you are closer to the provider's central office.
The connection is faster for receiving data than it is for sending data over the Internet.
The service is not available everywhere.

22. Cable Modems Uses coaxial cable already in place for your TV Drawbacks
Very fast transmission speed, especially for downloading
Always on: no need to dial a connection
Drawbacks
All users share a cable segment’s capacity
As more users in neighborhood go online, speed decreases
No security for individual users or data
Purchase a firewall program for security

23. Cellular Modems Transmit data over the cellular telephone system
Roughly half the speed of a regular telephone network

24. Data Transmission Simplex  sends data in one direction only
Example: television broadcasting
Half-duplex  sends data in both directions, but only one way at a time
Example: bank teller sends data about a deposit; after data received, a confirmation returns
Full-duplex  allows transmission in both directions at same time
Example: a conversation
Typically used for high-speed data communication

25. Communications Media Physical means of data transmission
Bandwidth is measure of the capacity of the communications link
Speed at which a line carries data and information
The faster the transfer rate, the faster you can send and receive data and information
Usually expressed as a measure of bits per second
bits per second (bps)
kilobits per second (Kbps)
megabits per second (Mbps)
gigabits per second (Gbps)

26. Types of Communications Media
Wire pairs
Coaxial cables
Fiber optics
Microwave transmission
Satellite transmission
Wireless transmission

27. Wire Pairs Also known as twisted pair Inexpensive
Two wires twisted around each other to reduce electrical interference
Inexpensive
Already in place (for telephone systems)
Susceptible to electrical interference and noise
Noise - anything that causes signal distortion

28. Coaxial Cable
A center conductor wire surrounded by layer of insulation and metallic sheath
Commonly used to connect to cable TV
Higher bandwidth and less susceptibility to noise than twisted pair

29. Fiber Optics Use light instead of electricity to send data
Much higher bandwidth than coaxial cable
Immune to electrical interference
Materials cheaper than coaxial, but installation costs high

30. Microwave Transmission
Uses line-of-sight transmission of data signals
Sending microwave must “see” receiver
Requires relay stations approximately every 30 miles
Waves are straight, earth is curved
Offers high speed and cost-effectiveness
Susceptible to weather conditions

31. Satellite Transmission
A form of microwave transmission
Satellite acts as relay station
Components
Earth station sends and receives signal to satellite
Transponder receives and amplifies signal, changes frequency, and retransmits data
Useful when signal must travel thousands of miles

32. Wireless Transmission
Transmits data over relatively short distances without wires
Examples
IrDA - uses infrared line-of-sight
Bluetooth - uses radio waves to connect mobile devices
standards - govern wireless transmission

33. Setting Standards
Protocol - a set of rules for the exchange of data between a terminal and a computer or two computers
Agreement on how data is to be sent and receipt acknowledged
Needed to allow computers from different vendors to communicate
Transmission Control Protocol/Internet Protocol (TCP/IP) permits any computer to communicate with the Internet