Packet Level Diagnostics and Protocol Analysis Questions

Using packet capture and analysis to diagnose protocol level behavior and network faults. Skills include capturing traffic with tcpdump, analyzing capture files with Wireshark or tshark, applying capture and display filters, following protocol streams, and reconstructing exchanges. Candidates should understand Transmission Control Protocol handshake and sequence semantics, retransmissions and duplicate acknowledgement patterns, congestion and flow control signals, User Datagram Protocol characteristics, fragmentation and maximum transmission unit issues, checksum and format anomalies, and how to correlate packet level traces with application logs and metrics to attribute latency or failures. Also cover techniques for capturing at multiple points, interpreting timestamps, and using packet analysis to validate fixes.