Fragmentation considered harmful
SIGCOMM '87 Proceedings of the ACM workshop on Frontiers in computer communications technology
Measuring interactions between transport protocols and middleboxes
Proceedings of the 4th ACM SIGCOMM conference on Internet measurement
Over-Zealous Security Administrators Are Breaking the Internet
LISA '02 Proceedings of the 16th USENIX conference on System administration
Inferring and debugging path MTU discovery failures
IMC '05 Proceedings of the 5th ACM SIGCOMM conference on Internet Measurement
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Path MTU Discovery (PMTUD) is widely believed to be unreliable because of firewalls that discard ICMP "Packet Too Big" messages. This paper measures PMTUD behaviour for 50,000 popular websites and finds the failure rate in IPv4 is much less than previous studies. We measure the overall failure rate between 5% and 18%, depending on the MTU of the constraining link. We explore methods webserver operators are using to reduce their dependence on PMTUD, and find 11% limit themselves to sending packets no larger than 1380 bytes. We identify a number of common behaviours that seem to be software bugs rather than filtering by firewalls. If these are corrected PMTUD failures could be reduced by 63%. We further find the IPv6 failure rate is less than the IPv4 rate even with more scope for failure in IPv6.