tracepath and Path MTU Discovery on Linux
Small things work and big things hang. One unprivileged command finds the narrow link, and one iptables rule shows what a black hole looks like.
MTU
Packet size, and the failures that only show up on large transfers. Articles tagged MTU cover path MTU discovery, the DF bit, MSS clamping, and the ICMP filtering that turns a narrow link into a black hole.
Latest posts
Testing MTU With Ping and the DF Bit
Find the path MTU with nothing but ping, from Linux and IOS XE, against a real 1400-byte link. The 28-byte math and the PMTUD black holes that hang TCP.