Which component helps diagnose performance issues within a network?

The network sniffer is the correct choice for diagnosing performance issues within a network because it captures and analyzes data packets traveling across the network. This tool provides insight into the traffic patterns, bandwidth usage, and potential bottlenecks by allowing administrators to see detailed information about the data being transmitted. By monitoring the network in real-time, a network sniffer can help identify issues such as high latency, packet loss, or network congestion, enabling more effective troubleshooting.

In contrast, while a router directs data packets between different networks and plays a crucial role in overall network functionality, it does not provide the detailed analysis of traffic patterns that a sniffer does. An access point primarily serves to connect wireless devices to a wired network and does not diagnose performance issues directly. A firewall is designed to monitor and control incoming and outgoing network traffic based on predetermined security rules, but it does not focus on the performance metrics or network health necessary for diagnosing issues. Each of these components serves important functions within a network, but the network sniffer stands out specifically for performance diagnostics.