_______ is an application layer protocol while _______ is internet layer protocol in TCP/IP reference model.

Question

Accepted Answer

The correct option is (1):
RTP, or Real-time Transport Protocol, is correctly classified as an **Application Layer** protocol within the TCP/IP model. While it often works closely with UDP at the Transport layer, RTP's primary function is to provide end-to-end network transport capabilities for applications transmitting real-time data, such as audio and video streaming, ensuring timely delivery and handling issues like jitter. ICMP, or Internet Control Message Protocol, is an integral part of the **Internet Layer** (or Network Layer in OSI) of the TCP/IP suite. Its vital role is to send error messages and operational information, typically related to a failed delivery of a datagram. For example, the "ping" utility relies on ICMP messages to determine if a host is reachable and calculate the round-trip time. Therefore, the pair RTP (Application Layer) and ICMP (Internet Layer) perfectly satisfies the criteria of the question.

The incorrect option is (2):
The pairing DSL, IP is incorrect because DSL (Digital Subscriber Line) is not an Application Layer protocol. DSL is a set of technologies used to transmit digital data over local telephone lines, operating primarily at the Physical and Data Link layers of the TCP/IP model. Its function is hardware-based data transfer, not application-level messaging. While IP (Internet Protocol) is correctly placed at the Internet Layer, the first component, DSL, fails to meet the requirement of being an Application Layer protocol.

The incorrect option is (3):
The option SONET, DSL is incorrect as neither term is classified as a protocol operating at the Application or Internet layers. SONET (Synchronous Optical Networking) is a physical layer standard that defines the transmission of a large amount of data over optical fiber. As established, DSL is a Physical/Data Link layer technology for local loop transmission. Both SONET and DSL describe lower-layer physical media or standards rather than the higher-level protocols needed for the specified layers.

The incorrect option is (4):
The pairing DNS, TCP is incorrect because while DNS (Domain Name System) is accurately an **Application Layer** protocol, the second protocol, TCP (Transmission Control Protocol), is classified at the **Transport Layer**, not the Internet Layer. The Transport Layer is responsible for segmenting and reassembling data and providing reliable, connection-oriented communication between applications. The Internet Layer, where IP resides, is concerned only with host-to-host packet delivery across network boundaries and does not include TCP's functionality.