UNIT 11
Introduction to Application Layer
The top most layer of OSI Model is application layer. Manipulation of data (information) in many ways is done in application layer which enables users or software’s to get access to any of the network. Some of the services provided by the application layer which includes: E-Mail, transferring files, distributing the results to user, directory services, network resources, and many more.
The Application Layer contains many protocols that are basically used by users. One of the widely-used application protocols is HTTP (Hypertext Transfer Protocol), which is the basis for the World Wide Web. When a browser wants a web page to come, it sends the name of the page it wants then the server using HTTP. The server then sends the page back to the users.
Some of the other application protocols that are used are: File Transfer Protocol (FTP), and Trivial File Transfer Protocol (TFTP), and Simple Mail Transfer Protocol (SMTP), andTELNET, andDomain Name System (DNS) etc.
Functions of Application Layer
- Mail Services: It is the basis for E-mail forwarding and storage of the mail.
- Network Virtual Terminal: It allows different user to log on to a remote host. This application creates the software emulation of a terminal at the remote host end. User's computer talks to the software terminal which in turn again talks to the host and vice versa. Then the remote host believes that it is communicating with one of its own terminals and then allows user to log on.
- Directory Services: This layer provides access for global information about many services.
- File Transfer, Access and Management (FTAM): It is a standard mechanism to access files and to manage it. Users can access files in the remote computer also and manage it. They can also retrieve files from that of the remote computer.
TCP/IP means Transmission Control Protocol and Internet Protocol. It is the network model which is used in the current Internet architecture also. Protocols are the set of rules which govern every possible communication aspects over a network. These protocols describe the movement of data between the source and the destination or that of the internet. They also offer very simple name and addressing schemes.
Protocols and networks in the TCP/IP model:
Overview of TCP/IP reference model
TCP/IP that is Transmission Control Protocol and Internet Protocol was developed by Department of Defence's Project Research Agency (ARPA, later DARPA) as a part of a research project of network interconnection to connect remote machines.
The features that come out during the research, which lead to making the TCP/IP reference model, were as shown below:
- It supports for a very flexible architecture. It was easy to add more machines.
- It was a robust network, and connections remained intact until the source and destination machines were functioning together.
The overall idea was to allow one application on any one of the computer to talk to (send data packets) another application which was running on different computer.
References:
- Data Communication & Networking by Forouzan, Tata McGraw Hill.
- Computer Network, 4e, by Andrew S. Tenenbaum, Pearson Education/ PHI.
- Data Communication and Computer Networks, by Prakash C.Gupta, PHI.
- Networking Ali-in-one Desk Reference by Doug Lowe, Wiley Dreamtech
- Computer Networking: A Top-Down Approach featuring the Internet, 3e by James F.Kurose.
- Computer Network by Godbole, Tata McGraw Hill.
- Computer Networking, by Stanford H. Rowe, Marsha L. Schuh
UNIT 11
Introduction to Application Layer
The top most layer of OSI Model is application layer. Manipulation of data (information) in many ways is done in application layer which enables users or software’s to get access to any of the network. Some of the services provided by the application layer which includes: E-Mail, transferring files, distributing the results to user, directory services, network resources, and many more.
The Application Layer contains many protocols that are basically used by users. One of the widely-used application protocols is HTTP (Hypertext Transfer Protocol), which is the basis for the World Wide Web. When a browser wants a web page to come, it sends the name of the page it wants then the server using HTTP. The server then sends the page back to the users.
Some of the other application protocols that are used are: File Transfer Protocol (FTP), and Trivial File Transfer Protocol (TFTP), and Simple Mail Transfer Protocol (SMTP), andTELNET, andDomain Name System (DNS) etc.
Functions of Application Layer
- Mail Services: It is the basis for E-mail forwarding and storage of the mail.
- Network Virtual Terminal: It allows different user to log on to a remote host. This application creates the software emulation of a terminal at the remote host end. User's computer talks to the software terminal which in turn again talks to the host and vice versa. Then the remote host believes that it is communicating with one of its own terminals and then allows user to log on.
- Directory Services: This layer provides access for global information about many services.
- File Transfer, Access and Management (FTAM): It is a standard mechanism to access files and to manage it. Users can access files in the remote computer also and manage it. They can also retrieve files from that of the remote computer.
TCP/IP means Transmission Control Protocol and Internet Protocol. It is the network model which is used in the current Internet architecture also. Protocols are the set of rules which govern every possible communication aspects over a network. These protocols describe the movement of data between the source and the destination or that of the internet. They also offer very simple name and addressing schemes.
Protocols and networks in the TCP/IP model:
Overview of TCP/IP reference model
TCP/IP that is Transmission Control Protocol and Internet Protocol was developed by Department of Defence's Project Research Agency (ARPA, later DARPA) as a part of a research project of network interconnection to connect remote machines.
The features that come out during the research, which lead to making the TCP/IP reference model, were as shown below:
- It supports for a very flexible architecture. It was easy to add more machines.
- It was a robust network, and connections remained intact until the source and destination machines were functioning together.
The overall idea was to allow one application on any one of the computer to talk to (send data packets) another application which was running on different computer.
References:
- Data Communication & Networking by Forouzan, Tata McGraw Hill.
- Computer Network, 4e, by Andrew S. Tenenbaum, Pearson Education/ PHI.
- Data Communication and Computer Networks, by Prakash C.Gupta, PHI.
- Networking Ali-in-one Desk Reference by Doug Lowe, Wiley Dreamtech
- Computer Networking: A Top-Down Approach featuring the Internet, 3e by James F.Kurose.
- Computer Network by Godbole, Tata McGraw Hill.
- Computer Networking, by Stanford H. Rowe, Marsha L. Schuh
