Advanced Options
Session Keep Alive:
Specifies how often to send session keep alive packets on active sessions. This will keep connections that have stalled during a particular download session from timing out.
Windows default value is 60 minutes, we recommend to set it to 10 minutes.
NDI Cache:
NDI Cache is the size of the cache used to store source routing paths. It has a very large effect on the performance of your TCP connection.
If your MAXMTU is set to 576 or below, it’s recommended to set the NDI Cache to 16.
If your MAXMTU value is greater than 576 set your NDI Cache to 32.
Maximum Sessions Allowed:
Windows limits connections to a single HTTP 1.0 server to four simultaneous connections. Connections to a single HTTP 1.1 server will be limited to two simultaneous connections. The HTTP 1.1 specification (RFC2068) mandates the two connection limit while the four connection limit for HTTP 1.0 is a self-imposed restriction which coincides with the standard used by a number of popular Web browsers.
Use this option in order to increase the number of simultaneous downloads from the same web site.

MTU Auto Discover:
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.
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.
MTU Auto Discover is Enabled by Default.
Black Hole Detection:
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.
Black Hole Detect is disabled by default.