Topic 3 - Networks - Part 2 Flashcards
Protocol
Set of rules for data communication over a network
Data packet
Portion of a message that is transmitted through a network. Contains data such as check digits and destination address.
Data integrity
overall completeness, accuracy and consistency of data;
means that the information has not been changed / corrupted deliberately or accidentally during transmission, from source to destination. Checksum mechanisms provide data integrity.
Source integrity
It means that the identity of the sender has been validated. Digital signatures prove source integrity.
Flow Control
mechanism that ensures the rate at which
a sender is transmitting is in proportion with the receiver’s receiving capabilities. Flow control is utilized especially in cases where the sending device can send data much faster than the receiver can digest.
Congestion management
Congestion happens when the request on the network resources exceeds the offered capacity.
Deadlock
Deadlock is a situation in which two or more network competing actions are each waiting for the other to finish, and thus neither ever does. The persistence timer is used to resolve the situation.
Error checking and Error correction
A process to determine the error and The ability to repair the error.
Factors that affect speed of data transmission
- Bandwidth of the network
- Data transfer rate of storage devices
- Interferences
- Malicious software
- Number of connected devices
- Number of users’ and users demand at any particular time (traffic)
- Packet loss and retransmission
- Read speed of storage devices
- Slowest segment
- Speed, technology and capacity of the network server
- Time required for user authentication and various security checks that take place
- Type of files send
- Type of transmission medium
- User’s PC CPU speed
- User’s PC RAM/disk caching
- User’s PC various subsystem performance
Data compression
Data compression involves encoding
information to use fewer bits than the
original data entity.
2 types of data compression
Lossy data compression: With this compression method, some loss of information is acceptable and there is no way to get the original file back. Examples: JPEG, MPEG2.
Lossless data compression: this compression method reduces the number of bits by first identifying and then eliminating any statistical redundancy. There is no loss of information during lossless compression. Examples: compression- decompression
software.
Compression algorithms Graphics, sound, music and video formats use to decrease the
size of the original file have become ubiquitous on the Internet
The Graphics Interchange Format (GIF) is a graphic file format that is used extensively
on the Web and uses a form of lossless compression algorithm (if we are dealing with
a graphic file that has fewer than 256 colors).
Mp3 is an audio coding format that uses a form of lossy data compression. Almost all
music now comes in mp3 format and this format dominates the Internet.
MPEG-2 combines lossy audio data compression and Iossy video data compression methods and is used in the transmission of video over the Internet (e.g. movies).
Datagram Packet Switching
with this method, each packet contains the receiver address. The path that datagrams take between the same source and destination can be different.
Virtual Circuit Packet Switching
with this method, a route from source to destination is set up before any transmission takes place.
Encryption
Encryption is absolutely necessary to protect data from unauthorized access during Internet use or any other untrusted network. There are two computer encryption categories: Symmetric-key encryption, single key encryption or secret key encryption. The same key is used for encryption and decryption; Public-key encryption or asymmetric key encryption. This uses a public key for
encryption and a private key for decryption.
