The original title is "TCP MSS Clamping: Fixing Path MTU Black Holes by Rewriting the SYN"

Short summary

A hands-on networking lab demonstrating TCP MSS clamping to fix Path MTU Discovery black holes. A router rewrites the MSS field in passing TCP SYNs so both endpoints agree to send segments that fit the narrowest link, eliminating reliance on PMTUD. The lab uses containerlab with Docker and includes step-by-step commands for deploying, testing, and tearing down the topology.

• •Router rewrites SYN MSS to match the smallest MTU link on the path
• •Eliminates dependency on PMTUD when ICMP is filtered
• •Hands-on lab using containerlab, Docker, and iptables TCPMSS --clamp-mss-to-pmtu

Generated with AI, which can make mistakes.