1. NETWORKS AND TRANSITION MEDIA
CHAPTER 8:
NETWORKS AND TRANSITION MEDIA

2. Data Communication
The transmission of information to and from any computer and components which is configured within a computer network. A network that has additional services are used to transport information from devices at one location to another device at other locations.

3. Types of Data Communication
Sending of data request - from sender to receiver for some action to be performed
Response of data - from receiver back to sender
Network status and conformation- status of the system (e.g. system going down in 5 minutes)
Centralized control - sent between system components (e.g. printer out of paper)

4. Networks
A Network as it relates to the world of technology are two or more connected computers that have has the capability to share information and instructions.
Additional network advantages are sharing of other resources such as files, documents, print services exchange files, or allow electronic communications.

5. Types of Networks
The components that are used to formulate a network are of copper wire, fiber optics, microwaves stations, and communication satellites.
Networks Classifications:
Personal Area Network (PAN)
Local Area Network (LAN)
Wide Area Network (WAN)
Metropolitan Area Network (MAN)
Virtual Private Network (VPN)

6. Personal Area Network (PAN)
A computer network used for communication among computer devices close to one person
The range of a PAN is typically about feet, but this is expected to increase with the advancement of technology yearly.
Examples:
Printers
Fax machines
Cellphones
Scanners.

7. Local Area Network (LAN)
A standard LAN configuration, one computer is designated as the file server. This computer will store all of the software that controls the network, as well as the software that can be shared by the computers attached to the network.
Dimensions
Communication/Transmission technology
Topology
Distinguished by Characteristics:

8. Local Area Network (LAN)
LANs are not strictly defined but below are the standard characteristics:
The transmission media is shared by all the connected devices in the network.
Each device is connected in the network and can operate stand alone or in the network.
Data transfer rates are high, usually 1 Mbps- 100 Mbps (Millions of bits per second).
Cost of setting up the network is usually low.
Area covered is small.

9. Wide Area Network
A computer network that connects larger geographic areas, such as the entire United States, or the world. Dedicated cable that is ran on the bottom of the ocean or satellite uplinks may be used to connect this type of network
The largest and most well-known example of a WAN is the Internet.

10. Wireless Network
Wireless networks are available in many forms, think of your universities which allows you to connect to the internet regardless of your location as long as you are located on campus.
Advantages
Easy Safekeeping.
We have a central location
Ease for software and system Management.
We can share most resources.
Management and generate E- Mail.
Speed
Disadvantages
Very Expensive to Install.
Extensive labor and maintenance time needed.
Server Fails everything fails unless you have a backup.
Hardware failure.

11. Metropolitan Area Network (MAN)
A bigger version of a LAN and normally uses similar technology. It might cover a group of nearby corporate offices or a city and might be either private or public. A metropolitan area network can also connect two or more local area networks together for a large campus area and even the school district in which you reside.

12. Virtual Private Network (VPN)
A computer network technology that creates an encrypted connection over a less secure network. The benefit of using a secure VPN is it ensures the appropriate level of security to the connected systems when the underlying network infrastructure alone cannot provide it.

13. Network Topologies
The structure of the network. This is considered as the physical configuration layout of all the connected devices. The characteristics of a network will depend upon the network topology selected.
There are two types of topology: physical and logical. The term "logical" here is very significant to a network. A network topology is independent of the "physical" layout f the network. The logical network topology is not necessarily the same as the physical layout.

14. Network Topologies
There are several types of topology design which can be used to implement an network such as LAN.
The majority of these are based on four types of topologies:
Mesh
Star
Bus
Ring

15. Mesh Topology
A mesh network is a network topology in which each node connected to each other which is a fully connected network. All mesh nodes are designed to distribute the data all over a network.
Advantage
Mesh network are wired networks to take advantages of security and reliability features.
Disadvantage
Difficult to configure and expensive to have redundant connection to every computer.

16. Star Topology
A star topology is comprised of a number of stations in which are channeled directly to a central station or controller.
The central controller manages and controls all communication between stations on the network.

17. Star Topology Advantages of a Star Topology Easy to install and wire.
Good performance
No disruptions to the network then connecting or removing devices.
Easy to detect faults and to remove parts.
Disadvantages of a Star Topology
Expensive to install because it requires more hardware.
Requires more cable length than a linear topology.
If the hub fails, nodes attached are disabled.

18. Bus Topology
All workstations and peripherals are connected to a single communication line using a media such as linear cable. This single communication line is referred to as a bus.
Information frames originating at a station are propagated away from the station in both directions on the bus.

19. Bus Topology
An extension to the bus topology is tree topology is in the following figure.
Tree topology extends the branches of the bus topology allowing more stations to access the bus.
On a bus or tree network there is no central point for management & control.

20. Bus Topology Advantages Initially less expensive than other topologies
Easy to connect a computer or peripheral to a linear bus.
Requires less cable length than a star topology.
Disadvantages
Entire network shuts down if there is a break in the main cable.
Maintenance costs may be higher in the long run.
Difficult to isolate the problem and troubleshoot.
Not meant to be used as a stand-alone solution in a large building.
Low security (all computers on the bus can see all data transmissions).

21. Ring Topology
This is a local area network that have each station attached to an adjacent station using point to point links from a physical ring.
Each station attached and active to the ring regenerate the information frame, then retransmits the information frame on the ring.
The ring itself is logically circle and the information travels in one direction.

22. Ring Topology Advantages This is well organized configuration
Data will flow in one direction
Fast
All the computers will share the same resources and data
Disadvantages
Data must pass through all computers
If one workstation fails, then entire network gets affected
There is no generally excepted taxonomy in which a computer network fit a design.

23. Broadcast Networks
These have a single communication channel that is shared by all computers on the network think of “amber alert”. Short messages in which data are transmitted are called packets.
An address field within the packet specifies the destination. Upon receiving a packet, the computer will check the address field to verify If the packet is intended for itself.

24. Point-to-Point Networks
This is comprised of several connection points between individual pairs of computers.
Multiple routes of different sizes are possible, so mapping of pathway such as an algorithm plays an important role in point-to-point networks.

25. Communication Components
Whenever we want two devices a transmitting and a receiving device is needed in order to communicate with each other. Below are the various components needed:
Sender and Receiver hardware
Communication devices
Communication channels

26. Sender and Receiver Hardware
Following hardware are used for handling communication messages, data transfer etc.

27. Workstations and Connections
Data communication is done using various communication devices and software’s interconnected for information exchange.
The devices used to communicate a data in communication network are called Workstations. These workstations may be computer, terminal, printer, telephones and other communication devices

28. Client/Server Network
Client/server operating systems allow the network to centralize functions and applications in one or more dedicated file servers.
The file servers become the heart of the system, providing access to resources and providing security.

29. Client/Server Network
Advantages
Centralized - Resources and data security are controlled through the server.
Scalability - Any or all elements can be replaced individually as needs increase.
Flexibility - New technology can be easily integrated into system.
Interoperability - All components (client/network/server) work together.
Accessibility - Server can be accessed remotely and across multiple platforms.
Disadvantages
Expense - Requires initial investment in dedicated server.
Maintenance - Large networks will require a staff to ensure efficient operation.
Dependence - When server goes down, operations will cease across the network.

30. Peer-to-Peer Network
Operating systems allow users to share resources and files located on their computers and to access shared resources found on other computers.
However, they do not have a file server or a centralized management source (See fig. 1).
In a peer-to-peer network, all computers are considered equal; they all have the same abilities to use the resources available on the network.

31. Peer-to-Peer Network Advantages Disadvantages
Less initial expense - No need for a dedicated server.
Setup - An operating system (such as Windows 95) already in place may only need to be reconfigured for peer-to-peer operations.
Disadvantages
Decentralized - No central repository for files and applications.
Security - Does not provide the security available on a client/server network.

32. IP Addresses
IP addresses are 32-bit numbers. They may be written in decimal, hexadecimal, or other formats, but the most common format is dotted decimal notation.
An IP address is formatted as a series of four values separated by periods: (colons) for example
The value of an IP address ranges from 0 through 255.

33. Network Ports
Ports are used to create a communication pathway between programs. A port is an address within a computer.
Port addresses are 16-bit addresses that are usually associated with a particular application protocol.
They are several types of servers in which provides a variety of services in which is accessible by users via the internet.

34. Network Ports Port Protocol Service description 21
File Transfer Protocol (FTP)
Transfers files 22
SSH (Secure Shell Protocol)
Allows secure remote administration through standard shell (console) 25
Simple Mail Transfer Protocol
Send 80
HyperText Transfer Protocol (HTTP)
Accesse the WWW (World Wide Web)
110
Post Office Protocol
Receive

35. Key Terms
Packetizing – Dividing a message into packets prior to transmitting the message over a communication medium.
Packet Switching - The transmission of a message by dividing the message into fixed-length packets and then routing the packets to the recipient. Packets may be sent over different paths and arrive out of order.

36. Key Terms
Routing - How the path from sender to receiver is determined.
Bandwidth - the capacity of a communications link measured in bits per second (bps) or bytes per second (Bps) bandwidth determines the time required to send data.
Standards - standards allow equipment from different manufactures to work together without standards the communications equipment would be more expensive and more difficult to use.

37. Voice over Internet Protocol (VoIP)
A category of hardware and software that enables people to use the Internet as the transmission medium for telephone calls by sending voice data in packets using IP rather than by traditional circuit transmissions.
Examples:
Vonage telephone services
Skype
Google voice.

38. Advantages of VoIP
One advantage of VoIP is that the telephone calls over the Internet do not incur a surcharge beyond what the user is paying for Internet access, much in the same way that the user doesn't pay for sending individual s over the Internet.

39. Privacy and Security Concerns
More channels of communication which means more possible security problems for corporations from having a network which promotes the following:
Hackers
Employee theft
Employee privacy issues
Viruses

40. Protocols
A set of rules that governs the communications between computers on a network.
These rules include guidelines that regulate the following characteristics of a network: access method, allowed physical topologies, types of cabling, and speed of data transfer.

41. Protocols Key Features
Define the rules that govern the communications between two computers connected to the network.
Roles: addressing and routing of messages, error detection and recovery, sequence and flow controls etc.
A protocol specification consists of the syntax, which defines the kinds and formats of the messages exchanged, and the semantic, which specifies the action taken by each entity when specific events occur.

42. Type of Transmission Media
Transmission media is a pathway that carries the information from sender to receiver for the transmission different types of cables or waves to transmit data are used.
There are three common types of bounded media used today for data transmission:
Coaxial Cable
Twisted Pairs Cable
Fiber Optics Cable

43. Coaxial Cable
Coaxial cable is very common & widely used commutation media. For example, TV wire is usually coaxial.
Coaxial cable gets its name because it contains two conductors that are parallel to each other.
The center conductor in the cable is usually copper. The copper can be either a solid wire or stranded martial.

44. Coaxial Cable DISADVANTAGE ADVANTAGES
Inexpensive
Bandwidth is high
Data transmission without distortion.
Used in long distance telephone lines.
Easy to wire
Easy to expand -They can span to longer distance at higher speeds as they have better shielding when compared to twisted pair cable
Much higher noise immunity
DISADVANTAGE
Single cable failure can take down an entire network
Difficult to install and expensive when compared with twisted pair.
If the shield is imperfect, it can lead to grounded loop.

45. Twisted Pairs Cable
The most popular network cabling is Twisted pair. It is light weight, easy to install, inexpensive and support many different types of network. It also supports the speed of 100 mbps.
Twisted pair cabling is made of pairs of solid or stranded copper twisted along each other.

46. Twisted Pairs Cable Advantages Disadvantages Characteristics
Advantages
Disadvantages
Characteristics
Easy installation
Capable of high speed for LAN
Low cost
Short distance due to attenuation
Subjected to moisture
Easy to install
High speed capacity
High attenuation (reduction in the strength of a signal)
100 meter limit

47. Fiber Optic Cable
Fiber optic cable uses electrical signals to transmit data. It uses light. In fiber optic cable light only moves in one direction for two way communication to take place a second connection must be made between the two devices.
In the center of fiber cable is a glass stand or core. No light escapes the glass core because of this reflective cladding.

48. Fiber Optic Cable Advantages Disadvantages
Fast -Provides high quality transmission of signals at very high speed.
Low attenuation
Used for both analog and digital signals.
No EMI interference- These are not affected by electromagnetic interference, so noise and distortion is very less.
Very expensive
Difficult to install.
Maintenance is expensive and difficult.
Hard to install

49. Radio Wave transmission
Example everyday technologies that depend on radio waves:
Wireless networks
Radio-controlled toys
Television broadcasts
Cell phones
GPS receivers
Satellite communications
Police radios

50. Microwave Transmission
Microwaves can be used to transmit signals over large distances if there are no obstacles between to reflect or absorb the beam.
Microwaves are used to send signals to and from satellites. The satellites can relay signals around the Earth.

51. Microwave Transmission
Advantages
We can receive phone calls and 24 hours a day
No wiring is needed to connect laptops to the Internet, or for mobile phones or radio
Communication with wireless technology is portable and convenient.

52. Microwave Transmission Properties
They are reflected by metal surfaces.
They pass through glass and plastics.
They pass through the atmosphere.
They pass through the ionosphere without being reflected.
They are absorbed by water molecules, how well depends on the frequency (energy) of the microwaves.
Transmission is affected by wave effects such as reflection, refraction, diffraction and interference.

53. Advantages of a Computer Network
1. Cost effective (Money saver)
2. Data, Information and Software Sharing
3. Hardware Sharing such as a printer
4. Internet Sharing
5. Broadcasting and Communication