ISSN 2320-5407 International Journal of Advanced Research (2016), Volume 4, Issue 6, 51-63 51 Journal homepage: http://www.journalijar.com INTERNATIONAL JOURNAL Journal DOI: 10.21474/IJAR01 OF ADVANCED RESEARCH RESEARCH ARTICLE COMPUTER NETWORK -- APPLICATION LAYER PROTOCOL. Rajesh Kumar 1 , Vivek Kumar Vaidya 2 . 1. Senior Lecturer, Department of Computer Science and Engineering, Govt. Polytechnic College, Ujjain-456001 (M.P.)-India. 2. Senior Lecturer, Department of Computer Science and Engineering, Jija Mata Govt. Polytechnic College, Burhanpur-450331 (M.P.)-India Manuscript Info Abstract Manuscript History: Received: 12 April 2016 Final Accepted: 19 May 2016 Published Online: June 2016 Key words: HTTP, DNS, TELNET, FTP, SMTP. *Corresponding Authors Rajesh Kumar, Vivek Kumar Vaidya. A majority of the internet uses a protocol suite called the Internet Protocol Suite also known as the TCP/IP protocol suite. This suite is a combination of protocols which encompasses a number of different protocols for different purpose and need. Because the two major protocols in this suites are TCP (Transmission Control Protocol) and IP (Internet Protocol), this is commonly termed as TCP/IP Protocol suite. This protocol suite has its own reference model which it follows over the internet. In contrast with the OSI model, this model of protocols contains less layers. An application layer is an abstraction layer that specifies the shared protocols and interface methods used by hosts in a communications network. The application layer abstraction is used in both of the standard models of computer networking; the Internet Protocol Suite (TCP/IP) and the Open Systems Interconnection model (OSI model). There are several protocols which work for users in Application Layer. Application layer protocols can be broadly divided into two categories. Copy Right, IJAR, 2016,. All rights reserved. Introduction:- An application layer is an abstraction layer that specifies the shared protocols and interface methods used by hosts in a communications network. The application layer abstraction is used in both of the standard models of computer networking; the Internet Protocol Suite (TCP/IP) and the Open Systems Interconnection model (OSI model). Although both models use the same term for their respective highest level layer, the detailed definitions and purposes are different. In TCP/IP, the application layer contains the communications protocols and interface methods used in process-to- process communications across an Internet Protocol (IP) computer network. The application layer only standardizes communication and depends upon the underlying transport layer protocols to establish host-to-host data transfer channels and manage the data exchange in a client-server or peer-to-peer networking model. Though the TCP/IP application layer does not describe specific rules or data formats that applications must consider when communicating, the original specification (in RFC 1123) does rely on and recommend the robustness principle for application design. [1] In the OSI model, the definition of the application layer is narrower in scope. The OSI model defines the application layer as the user interface responsible for displaying received information to the user. In contrast, the Internet Protocol model does not concern itself with such detail. OSI also explicitly distinguishes additional functionality below the application layer, but above the transport layer at two additional levels; the session layer and