Wireshark is a free and open-source network protocol analyzer. Its primary function is to capture network packets in real-time and display them in a human-readable format. It allows network administrators and security professionals to "see" the traffic on a network, inspect the contents of individual packets, and troubleshoot network problems. It deconstructs network protocols from the lowest layers (e.g., Ethernet) to the highest (e.g., HTTP), making it an indispensable tool for detailed network analysis.

A. Cisco AnyConnect is a unified security endpoint client that provides VPN access, not a tool for general packet analysis.

C. Oracle Database is a relational database management system (RDBMS) used for storing and managing data, unrelated to network traffic inspection.

D. Norton Antivirus is security software designed to detect and remove malware; its primary role is not packet analysis for troubleshooting.

1. Odom, W. (2019). CCNA 200-301 Official Cert Guide, Volume 1. Cisco Press. Chapter 2, "Fundamentals of Ethernet LANs," Section "Data-Link Frames," discusses using tools like Wireshark to view frame headers.

2. Wireshark Foundation. (n.d.). About Wireshark. Wireshark.org. Retrieved from https://www.wireshark.org/about.html. The first sentence states, "Wireshark is the world’s foremost and widely-used network protocol analyzer."

3. Kurose, J. F., & Ross, K. W. (2017). Computer Networking: A Top-Down Approach (7th ed.). Pearson. Chapter 1, Section 1.5.2, "Network Security," and various "Wireshark Labs" throughout the book demonstrate its use for packet sniffing and analysis.

4. McKeown, N. (2013). CS144: Introduction to Computer Networking. Stanford University. Lab 0, "Networking Basics," requires students to install and use Wireshark to capture and analyze HTTP traffic. Retrieved from https://cs144.github.io/assignments/lab0.pdf.