A system administrator is diagnosing severe packet loss and degraded throughput on a critical database server following an upgrade to a 10GBASE-SR fiber network interface card (NIC). According to the OSI bottom-up troubleshooting methodology, in what sequence should the administrator perform the following diagnostic steps to isolate the issue?
- 1Inspect the LC fiber optic patch cable connector tip with a fiber inspection scope and verify optical light levels using a power meter.
- 2Check the network interface counters for Frame Check Sequence (FCS) errors, cyclic redundancy check (CRC) errors, and run-length anomalies.
- 3Execute ICMP echo requests with varying payload sizes and the Don't Fragment (DF) bit set to determine the Maximum Transmission Unit (MTU) path path-MTU discovery status.
- 4Perform an end-to-end socket performance benchmark using iperf to measure TCP windowing negotiation and transport throughput across target ports.
Cevap
The correct sequence starts at Layer 1 (checking fiber optical power and physical cable connectors), proceeds to Layer 2 (checking NIC interface counters for FCS/CRC framing errors), moves up to Layer 3 (verifying IP layer MTU and ICMP packet fragmentation), and finishes at Layer 4 (testing TCP transport performance with iperf).
The standard OSI bottom-up troubleshooting methodology dictates verifying physical Layer 1 media (fiber optics/power levels) first. Next, Layer 2 data link integrity is assessed by inspecting NIC frame counters for CRC/FCS errors. Following frame verification, Layer 3 network layer metrics (IP fragmentation and path MTU) are diagnosed using ICMP. Finally, Layer 4 transport layer socket bandwidth and TCP windowing are benchmarked.
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OSI Model Bottom-Up Troubleshooting Methodology
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