What is a characteristic of IPv4 addresses?

An IPv4 (Internet Protocol version 4) address is a numerical label assigned to each device participating in a computer network that uses the Internet Protocol for communication. The defining characteristic of an IPv4 address is its length: it is a 32-bit number. This 32-bit address space allows for 2^32 (approximately 4.3 billion) unique addresses. The address is typically represented in human-readable dot-decimal notation (e.g., 192.168.1.1).

B. 128 bits is the length of an IPv6 address, the successor to IPv4, designed to overcome IPv4 address exhaustion.

C. 12 hex-digit notation is commonly used to represent a 48-bit MAC (Media Access Control) address, not an IPv4 address.

D. The zero compression rule, which allows consecutive fields of zeros to be abbreviated with a double colon (::), is a feature of IPv6 addressing.

1. Postel, J. (1981). Internet Protocol. RFC 791. Section 3.2 "Addressing" states, "A 32-bit address is used as a source and destination address."

2. Deering, S., & Hinden, R. (2017). Internet Protocol, Version 6 (IPv6) Specification. RFC 8200. Section 3 "IPv6 Header Format" specifies the 128-bit source and destination addresses.

3. MIT OpenCourseWare. (2018). 6.033 Computer System Engineering, Spring 2018. Lecture 13: The Network Layer. This lecture material details the 32-bit structure of IPv4 addresses.