The statement is incorrect. The "Protocol" field in the IPv4 header identifies the next-level protocol encapsulated within the IP datagram. According to the Internet Assigned Numbers Authority (IANA), the assigned protocol number for the User Datagram Protocol (UDP) is 17. The protocol number 6 is reserved for the Transmission Control Protocol (TCP). Therefore, if the transport-layer protocol is UDP, the value in the network layer's "Protocol" field must be 17, not 6.

This is a True/False question. The statement is factually incorrect as the protocol number for UDP is 17. The number 6 corresponds to TCP.

1. Postel, J. (1981). RFC 791: Internet Protocol. Internet Engineering Task Force. Section 3.1, "Header Format". This document defines the Protocol field in the IPv4 header.

2. Postel, J. (1980). RFC 768: User Datagram Protocol. Internet Engineering Task Force. This document defines UDP.

3. Internet Assigned Numbers Authority (IANA), "Protocol Numbers". The official registry lists UDP as protocol number 17 and TCP as protocol number 6.