Application Layer Protocols in Internet

The Internet Protocol Suite consists of four layers, namely, application layer, transport layer, internet layer, and link layer. The application layer is the topmost layer that interacts with the end-users and provides services for communication over the network. It includes various protocols that enable different applications to communicate with each other. Some of the popular application layer protocols used in the internet are:

1. Remote Procedure Call (RPC): It is a protocol that allows a program to execute a subroutine or procedure on a remote computer or server. It is used for distributed computing and enables different applications to communicate with each other across the network.

2. Internet Relay Chat (IRC): It is a protocol used for real-time internet chat and messaging. It allows users to communicate with each other in real-time and participate in group chats or channels.

3. Resource Reservation Protocol (RSVP): It is a protocol used for reserving network resources for specific data flows or applications. It enables the network to reserve bandwidth, delay, and other parameters to ensure quality of service (QoS) for the application data.

4. Hypertext Transfer Protocol (HTTP): It is a protocol used for transferring hypertext documents, such as HTML pages, over the internet. It enables the communication between web servers and web browsers and forms the backbone of the World Wide Web.

Not an Application Layer Protocol Used in Internet

The correct answer to the given question is option 'C', Resource Reservation Protocol (RSVP). Although RSVP is an application layer protocol, it is not widely used in the internet. It was initially developed as a QoS protocol for Integrated Services Model (ISM) networks, but later replaced by Differentiated Services (DiffServ) architecture. DiffServ is a more scalable and flexible approach for providing QoS in the internet, and it does not require explicit resource reservation like RSVP. Therefore, RSVP is not considered as a standard application layer protocol used in the internet.