COMMUNICATION PROTOCOL

A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications. A protocol may have a format description. Protocols may includes signaling, authentication and error detection or connection capabilities. A protocol definition defines the syntax, semantics and synchronization of communications; the specified behavior is typically independent of how it is to be implemented. A protocol can therefore be implemented as hardware or software or both.

TCP/IP

~TCP/IP is the communication protocol for communication between computers on the 

  Internet.

~TCP/IP stands for Transmission Control Protocol / Internet Protocol.

~TCP/IP defines how electronic devices (like computers) should be connected to the 

   Internet, and how data should be transmitted between them.

Hart communication protocol

HYPERTEXT TRANSFER PROTOCOL

~ The Hypertext Transfer Protocol (HTTP) is an application protocol for distributed, 

   collaborative, hyper media information systems. HTTP is the foundation of data 

   communication for the World Wide Web.

~  Hypertext is a multi-linear set of objects, building a network by using logical links 

   (the so-called hyperlinks) between the nodes (e.g. text or words). HTTP is the 

   protocol to exchange or transfer hypertext.

~ The standards development of HTTP was coordinated by the Internet Engineering 

   Task Force (IETF) and the World Wide Web Consortium (W3C), culminating in the 

   publication of a series of Requests for Comments (RFCs), most notably RFC 2616 

   (June 1999), which defines HTTP/1.1, the version of HTTP in common use.

SIMPLE MAIL TRANSFER PROTOCOL (SMTP)

~ Simple Mail Transfer Protocol (SMTP) is an Internet standard for electronic mail (e-mail) transmission across Internet Protocol (IP) networks. SMTP was first defined by RFC 821 (1982, eventually declared STD10), and last updated by RFC 5321 (2008) which includes the extended SMTP (ESMTP) additions, and is the protocol in widespread use today. SMTP uses TCP port 25. The protocol for new submissions (MSA) is effectively the same as SMTP, but it uses port 587 instead. SMTP connections secured by SSL are known by the shorthand SMTPS, though SMTPS is not a protocol in its own right.

While electronic mail servers and other mail transfer agents use SMTP to send and receive mail messages, user-level client mail applications typically only use SMTP for sending messages to a mail server for relatying. For receiving messages, client applications usually use either the Post office Protocol  (POP) or the Internet Message Access Protocol (IMAP) or a proprietary system (such as Microsoft Exchange or Lotus Notes/Domino) to access their mail box accounts on a mail server.

 Mail processing model

POST OFFICE PROTOCOL (POP)

~ In computing, the Post Office Protocol (POP) is an application-layer Internet standard protocol used by local e-mail clients to retrieve e-mail from a remote server over a TCP/IP connection. POP and IMAP (Internet Message Access Protocol) are the two most prevalent Internet standard protocols for e-mail retrieval. Virtually all modern e-mail clients and servers support both. The POP protocol has been developed through several versions, with version 3 (POP3) being the current standard. Most webmail service providers such as Hotmail, Gmail and Yahoo! Mail also provide IMAP and POP3 service.