What is the TCP/IP layer that includes the User Datagram Protocol (UDP)?

The User Datagram Protocol (UDP) operates at the Transport layer of the TCP/IP model. This layer is responsible for providing end-to-end communication services for applications. UDP offers a connectionless, unreliable datagram service, which is suitable for applications where speed is prioritized over reliability, such as video streaming or online gaming. It functions directly on top of the Internet Protocol (IP) to transmit datagrams between hosts. The Transport layer encapsulates application data into segments (for TCP) or datagrams (for UDP) and passes them down to the Internet layer for routing.

A. Application: The Application layer contains protocols that applications use to communicate (e.g., HTTP, DNS), but it relies on the Transport layer for data delivery.

B. Network or internet: The Network or Internet layer is responsible for logical addressing and routing using protocols like the Internet Protocol (IP), not for end-to-end data transport.

C. Physical or network access: This layer deals with the physical transmission of data over the network medium and hardware addressing (MAC addresses), not transport-level protocols like UDP.

1. Braden

R. (Ed.). (1989). Requirements for Internet Hosts -- Communication Layers. RFC 1122. Internet Engineering Task Force (IETF). Section 4

"TRANSPORT LAYER -- TCP and UDP

" explicitly defines both TCP and UDP as the primary protocols of the Transport Layer.

2. Postel

J. (1980). User Datagram Protocol. RFC 768. Internet Engineering Task Force (IETF). The document abstract describes UDP as a "datagram mode of packet-switched computer communication in the environment of an interconnected set of computer networks

" placing it as a transport mechanism above the Internet Protocol.

3. Kurose

J. F.

& Ross

K. W. (2021). Computer Networking: A Top-Down Approach (8th ed.). Pearson. Chapter 3

"Transport Layer

" Section 3.3

"Connectionless Transport: UDP

" details the function and placement of UDP within the Transport layer of the network stack.