MTU Auto
Discover: |
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Enabling this setting causes TCP to attempt to discover the Maximum Transmission Unit (MTU or largest packet size) over the path to a remote host. By discovering the Path MTU and limiting TCP segments to this size, TCP is supposed to be able to eliminate fragmentation at routers along the path that connect networks with different MTUs. This requires implementation of the corresponding server side algorithm, however, and presupposes all of the servers on the entire Internet only running MSFT server software with server-side optimization features accessible from MSFT web-browser client software. Needless to say, this is rather unlikely. |
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Nevertheless, it is not recommended to disable this setting as it would then cause an MTU of 576 bytes to be used for all connections that are not to machines on the local subnet. Disabling this setting can cause severe performance degradation because fragmentation may not be compensated for. |
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MTU Auto Discover is Enabled by Default. |
Black
Hole Detection: |
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Black Hole Detection specifies whether the stack will attempt to detect Maximum Transmission Unit routers that do not send back ICMP fragmentation-needed messages. Enabling black hole detection increases the maximum number of re-transmissions performed for a given segment. Setting this parameter 'enabled', when it is not needed, can cause performance degradation. If the router is not sending back the ICMP messages, then PMTU will not work. This can cause an even greater loss of performance. It is recommended that PMTU Black Hole Detect be disabled. |
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Black Hole Detect is disabled by default. |