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This article walks through a real‑world case where an app’s content loading fails due to MTU/MSS mismatches, explains how packet captures reveal retransmissions and missing ACKs, demonstrates ping‑based MTU probing, and shows how oversized request parameters in a new version caused the issue.
The investigation used Wireshark captures to uncover that a new app version sent oversized TCP segments—due to altered MSS and path‑MTU mismatch—causing unacknowledged retransmissions, which were diagnosed with ping‑do‑not‑fragment tests and resolved by trimming the request parameters and confirming via TLS key logging.
When running Jenkins inside a Docker container on a VM, HTTPS requests to accounts.google.com time out due to an MTU mismatch between the host and the container, which can be resolved by adjusting the MSS via iptables or setting a lower MTU for Docker interfaces.
This article explains the structure of Linux network I/O by detailing the OSI seven‑layer model, the role of each layer, MTU/PMTU concepts, IP fragmentation and reassembly, and key TCP mechanisms such as MSS, flow control, and congestion control, providing a comprehensive foundation for studying zero‑copy networking.
This article explains why the Ethernet maximum transmission unit (MTU) settled on 1500 bytes, covering early hardware constraints, cost considerations, the emergence of jumbo frames, modern traffic analysis, and why changing this long‑standing value remains difficult.