What is passive and active measurement ?

Passive measurement refers to the collection of data without actively interacting with the system being measured. This can involve monitoring network traffic, collecting logs, or analyzing data that is already being generated by the system.

Active measurement, on the other hand, involves actively sending probes or test packets to measure the performance or behavior of a system. This can include sending ping requests, traceroute tests, or other types of active tests to gather data about the system's performance.

Both passive and active measurement techniques have their own advantages and limitations, and are often used in combination to provide a more comprehensive understanding of a system's behavior.

Passive Measurement

- Definition: Monitoring network traffic without interacting with it.
- Method: Sniffing or capturing packets using tools like Wireshark or tcpdump.
- Advantages:
- Unaffected by measurement process.
- Provides detailed insights into traffic patterns, performance, and security issues.
- Disadvantages:
- Only captures packets that the sensor can see.
- Difficult to capture traffic on all segments of a network.

Active Measurement

- Definition: Probing the network with test packets to measure performance metrics.
- Method: Sending ICMP echo requests (ping), traceroute, and bandwidth measurement tools.
- Advantages:
- Can measure performance metrics (e.g., latency, throughput) directly.
- Allows for comparison of different network paths.
- Disadvantages:
- Can affect network performance if too many probes are sent.
- May not capture real-world traffic conditions.