Network Protocol Internals and Edge Cases Questions
Deep understanding of how protocols work internally (TCP congestion control, IP fragmentation, DNS resolution under failure, IPv6 transition), edge cases that cause problems, and protocol troubleshooting.
MediumTechnical
20 practiced
In a Kubernetes cluster, pods intermittently experience connection resets when calling an external API. Describe how you would triage across layers: pod network namespace, CNI plugin, kube-proxy/iptables or IPVS, node networking, and cloud VPC. Include commands and observability checkpoints you would use.
HardTechnical
25 practiced
Out-of-order packets are causing excessive retransmissions and application timeouts on some flows. Describe kernel and application-level knobs to tolerate packet reordering (for example Linux reorder thresholds and PAWS), and discuss fallback strategies such as application-level sequencing or NACK-based protocols. Evaluate trade-offs for each approach.
HardBehavioral
21 practiced
You're the on-call SRE lead during an incident where a PMTU black hole caused 30% of client traffic to fail for a critical API. Describe how you would lead the incident: initial triage steps, communication cadence to stakeholders, short-term mitigations to restore service, the post-incident review plan, and how you would prioritize technical fixes versus process changes.
MediumTechnical
24 practiced
Implement exponential backoff with jitter for DNS retry logic in Python. Requirements: configurable base interval, exponent/backoff factor, maximum backoff cap, max retries, support for full and half jitter modes, and a pluggable predicate to decide whether to retry. Provide code or clear pseudocode.
HardTechnical
22 practiced
You suspect a transit provider is using transparent TCP proxies that strip or modify TCP options, leading to degraded performance. Describe active and passive detection techniques you would execute from endpoints and management hosts, and propose mitigation strategies (routing changes, encapsulation, or negotiating with the provider).
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