Tag Archive for HTTP

How does Email work?

Protocols used in email transfer

This post gives a basic overview of the theory of operation of Electronic Mail (Email). It also explains the different components of an electronic mail system like User Agents (UAs), Mail Transfer Agents (MTAs) and Mail Access Agents (MAAs).

Role and Types of Application Layer Protocols

Two broad categories of application layer protocols based on whether they use TCP or UDP

This post gives a brief overview of the role of application layer protocols. It also gives a brief overview of the different methods of classification of application layer protocols like network service based classification or peer relationship based classification.


It consists of a set of hardware components and a suite of Network software protocols
Basic building blocks of a computer networks

Basic building blocks of a computer networks

Hardware components consists of End Nodes (sending/receiving computers), Intermediate Nodes (Routers/Switches/hubs etc. that are part of the data exchange) and telecommunication links (wired/wireless media, cables, connectors etc.).
End Nodes:
  • Computer or any embedded system with Network Hardware and Software.
  • Hardware typically consists of add-on-cards called Network Interface cards (NICs). The NICs implement some of the communication protocols in hardware, so as not overburden the main CPU. The NICs also interfaces  to the   telecommunication links, that connect the end nodes to the network.
  • While certain lower layer protocols are implemented in hardware, lots of higher layer protocols like TCP, IP, FTP, HTTP etc. are implemented in software.
  • Actual communication of meaningful data happens between a sending computer and a receiving computer.
  • Data is split into smaller units called packets by the sending computer and then handed over to the data exchange devices, to be carried over to the receiving computer
Examples of End Nodes in a Computer Network

Examples of End Nodes in a Computer Network

  • These are special purpose computers/embedded systems used  only for data transfer between end nodes
  • These devices are part of the data exchange and are used to route data packets between the sending and receiving computers.
  • E.g.: Packet Switches (Routers/Switches), Hubs, Repeaters, Modems, Satellites etc.
Examples of Intermediate nodes in a computer Network

Examples of Intermediate nodes in a computer Network

Telecommunication Links
  • Consists of Wired and wireless medium that actually carries the electrical/optical/electromagnetic signals. 
  • Just like vehicles need roads to move, computers require wired/wireless telecommunication links to carry the signals between them.
  • Includes cables (e.g. twisted pair copper, coaxial etc.) and connectors (e.g. RJ-11, RJ-45 etc.) for wired media
  • Includes different types of antennae for wireless media
Examples of Wired and Wireless Communication links

Examples of Wired and Wireless Communication links

Network Software
  • Wide range of protocols developed specifically for computer communication (E.g. IP, TCP, UDP etc.)
  • A protocol is a set of rules developed for a very specific purpose
  • Consists of core communication protocols (like IP, TCP, UDP etc.) and also application specific protocols (like HTTP, FTP, SMTP etc.)
  • Includes device drivers written for specific hardware (E.g. Ethernet device drivers)