Network Protocols and Layers

• Networking protocols define rules and conventions for communication.
• Protocols define the speed of transmission, size of the message, error checking methods and type of transmission.
• There are two types of transmission:

  1. Synchronous.
  2. Asynchronous.
• The protocols are established between sender and receiver before starting communication.
• Handshaking is the process of negotiation between the sender and receiver by an exchange of messages.
• Once handshaking is complete, data packets travel from sender to receiver through various routers.
• Data packets are exchanged between various routers; this is called packet switching.
• A data packet contains the sender's and receiver's address.
• An IP address is a unique address assigned to each device in a network.
• IP addresses consists of binary numbers and are usually represented in decimal or hexadecimal format.
• In IPv4, each device is assigned a 32-bit address. This means that around 14 billion unique IP addresses can be assigned. 8 bits form an octet. Each octet represent any number between 0 and 255.
• In IPv6, each device is assigned a 128-bit address.
• Static IP addresses are assigned by the network administrator. When the device is not in use, this address remains unused too.
• Dynamic Host Control Protocol (DHCP) is responsible for IP addresses being able to be reused when the device is not in use.
• MAC address is the address provided by the manufacturer that uniquely identifies the network interface card.
• IP addresses are provided by a network administrator (for a closed network) and defines the connection between network and device. They are assigned by a router in normal internet use.
• TCP/IP is a suite of communication protocols use to interconnect network devices of different manufacturers on the Internet.
• Hypertext Markup Language (HTML) is the standard markup language for creating web pages and web applications. It provides us with tags to design web-pages.
• HTML pages are written in Notepad and saved as an HTML file.
• Cascaded Style Sheets (CSS) is used to edit the appearance of the HTML components such as buttons, text boxes, etc.
• A CSS file is stored separately from its HTML file.
• The features of HTML are enhanced by using Extensible Markup Language (XML).
• The data used in HTML pages can be reused when XML is used.
• XML is used to store and transport data.
• Updating web pages is simpler when XML and HTML are used together.
• Hypertext Transfer Protocol (HTTP) is the set of rules used for transferring files such as resources on the Internet.
• HTTP is a client-server protocol for requesting data through an HTML page and delivering data.
• A secure form of HTTP is HTTPS, which is used for sensitive information.
• HTTPS provides authentification between web server and its user to make sure that the user is communicating with the intended sever.
• Simple Mail Transfer Protocol (SMTP) is respnsible for sending an email.
• Post Office Protocol (POP3) is responsible for receiving an email.
• POP3 downloads the email from the server and stores it on the client's computer.
• Internet Message Access Protocol (IMAP) is a protocol to access email messages. It is more efficient than POP. It takes up the complete responsibility of managing a remote mailbox.
• Voice Over Internet Protocol (VOIP) is a set of protocols that enable us to make voice calls over the Internet.
• File Transfer Protocol (FTP) defines the set of rules for transferring large files on the Internet.
• The files required for a website are organised on a web server using FTP.
• Layering is when a complex process is broken into several processes or layers in a particular order.
• Layers help to solve a complex problem by dividing it into a set of simple layers.
• Interoperability is when layers permit different systems and software applications to communicate with each other.
• TCP/IP states the rules according to which data is formatted, segmented, addressed, routed and received.