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Ch.17 Communication Software and Protocols - Coggle Diagram
Ch.17 Communication Software and Protocols
The need for communication software
message
text
image
audio
video
services
Sharing data or information
Real-time communication between people in different locations through computer networks.
Broadcasting messages
advantages
Much lower cost of transmission
Support multimedia message
Transmitted information is reusable in most cases
Instant or much higher transmission speeds
applications
E-mail
Video conferencing
Instant messaging
Internet phones
Chat rooms
Newsgroups
Discussion forums
The application used to transmit digital messages from one user to another through a computer network
The need for communication protocols
Each type of network application requires a communication protocol to transmit its data over a computer network
Communication software utilizes communication protocol to work with communication devices
need
Necessary to define a common standard that is understood by all devices
Computer network may consist of a large variety of computer systems and electronic equipment.
Communication Protocol
Transmission Control Protocol/ Internet Protocol (TCP/IP)
Simple Mail Transfer Protocol (SMTP)
Wireless Application Protocol (WAP)
Internet Fax Protocol (IFP)
Voice over Internet Protocol (VoIP)
A set of rules about data formatting or signalling that is understood by all the communication devices
Open System Interconnection (OSI) model
Application layer
Provides the interface for application software to set up communication with another application software
Presentation layer
Converts data into a format that can be transmitted.
Compatible to the receiver’s system
Session layer
Responsible for setting up and maintaining the communication linkages between two computers in computer network during data transmission.
Transport layer
Adds a Transport Header (TH) to data to form a datagram.
TH contains the transportation information such as the protocol used.
For those datagrams transmitted over the Internet using Transmission Control Protocol (TCP), they will be divided into smaller packets before transmitting to the next layer
Network layer
Determines the routing and forwarding of data.
Adds a Network Header (NH) to a datagram to form a packet.
NH contains network address information.
Internet Protocol (IP): example of the implementation of the network layer.
Data link layer
Responsible for the network addressing as well as error detection and correction
A header and a trailer are added to a packet to form a frame.
Data Link Header (DLH) contains the physical address and the method of error detection and correction.
Data Link Trailer (DLT) is a string of bits that indicates the end of the packet.
Physical layer
Transfers frames physically on a LAN.
Responsible for managing the interaction between communication devices in a computer and a network medium.
Domain names and domain name systems
Uniform Resource Locator (URL)
Refers to a particular web page of a file residing on a web site.
It must contain the protocol to be used and the domain name.
A folder name and a file name on the web server relative to the web server’s root directory can also be appended to the URL.
Common that there is more than one server running in a domain
May access a specific server by adding a port number to the end of a URL.
If no port number is specified in a URL, it is assumed that port 80 is used one the web server for communication.
Domain Name System (DNS)
Translates domain names to IP addresses.
Translation is known as name resolution.
Interprets the information in a domain name and searches for the associated IP address.
User can access the information of a registered domain by its domain name instead of its numeric IP address.
Domain names
Many organizations or companies like to use generic-code TLD names at the second-level
Non-US domain names use the country-code TLD, based on the country where the server is located.
Common generic-code TLD: com, edu, gov, org, mil and net.
Network Solutions
In charge of ensuring there is no duplication of a domain name.
When register a domain name, it will add the domain name to its central database.
Official terminology of this kind of name is Fully Qualified Domain Name (FQDN).
Hong Kong Internet Registration Corporation Limited (HKIRC)
Responsible for managing the registry of Internet domain names under ‘.hk’ counter-code TLD.
IP address of a web site on the Internet is usually associated with an easy-to-remember name
Much easier to memorize meaningful words
internet protocol address
Format of an IP address:
32-bit numeric address
Expressed as four denary numbers separated by periods.
Each number can fall between 0 and 255 inclusively
consists of two parts
network address: identify a particular network.
host address: identify a particular device in the network
ICANN is responsible for registering and maintaining the com, net and org top-level domain names on the WWW.
the number of addresses based on IPv4 is not large enough to fulfill the current growth rate of the Internet
IP addresses issued by the Internet Corporation for Assigned Names and Numbers (ICANN).
A new address system Internet Protocol Version 6 (IPv6) can accommodate more IP address.
Can identify every computer in a network.
This address system is known as Internet Protocol Version 4 (IPv4)
IP addresses, Unique in the network
Data transmission oever the internet
Transmission Control Protocol/Internet Protocol (TCP/IP)
TCP and IP sends data over a packet switching network
To transmit data over the Internet:
Data has to be processed through series of layers to that the data conforms to a common standard
two main protocols
TCP
Manages data packets and network information necessary for efficient routing.
When a data file is sent through a network using TCP
The file is divided into one or more packets.
The packets are numbered and the forwarded one by one to the IP layer.
When the packets arrive at the receiver’s computer, the TCP layer reassembles the received data packets into a single data file.
A transport layer protocol in the OSI seven layers model
IP
A network layer protocol in the OSI seven layers model
Handles the actual delivery of data packets.
Responsible for
Adding the destination IP address to every packet for routing the packet to the destination through the network server.
Packet fragmentation to reduce the size of the original packet to pass through some network servers with small maximum packet size (Maximum Transmission Unit).
Selects the shortest path to the destination
Chooses an alternative path to avoid network congestion
A communication protocol suite used in the construction of the Internet and numerous computer networks
Process of data transmission over the Internet
Hypertext Transfer Protocol (HTTP)
An application protocol that is built on top of TCP
Used to transfer hypertext documents called web pages
Web pages
Stored on millions of servers around the world that are connected to the Internet.
Electronic document written in the hypertext format .
Can be interpreted and displayed by a web browser (HTTP client).
May contain
Hyperlinks to other web pages
Tags guiding the web browser to how text and multimedia elements are displayed on a computer screen