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Traditional (RFC1191) Path MTU Discovery

RFC 1191 rfc1191 describes a method for a sender to detect the Path MTU to a given receiver. (RFC 1981 rfc1981 describes the equivalent for IPv6.) The method works as follows:

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This method is widely implemented, but is not robust in today's Internet because it relies on ICMP packets sent by routers along the path. Such packets are often suppressed either at the router that should generate them (to protect its resources) or on the way back to the source, because of firewalls and other packet filters or rate limitations. These problems are described in RFC 2923 rfc2923. When packets are lost due to MTU issues without any ICMP "Too Big" message, this is sometimes called a (MTU) black hole. Some operating systems have added heuristics to detect such black holes and work around them. Workarounds can include lowering the MTU estimate or disabling PMTUD for certain destinations.

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A user-space implementation over UDP is included in the VFER bulk transfer tool.

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-- HankNussbacher - 2005-07-03
– SimonLeinen - 2006-07-19 - 20172018-1207-0802