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Calculating the Merged Round-Trip Time

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[The TCP chimney offload feature is deprecated and should not be used.]

An offload target calculates the Merged Round-Trip Time (MRTT) as follows:

MRTT = ( NicTime+ NicDelta) - TsEchoed

This equation contains the following:

  • NicTime is the offload target's current time.

  • NicDelta is the offload target's timestamp delta.

  • TsEchoed is the timestamp that is echoed in the acknowledgement from the remote TCP peer.

The host stack calculates the MRTT in a similar way: it adds its timestamp delta to its current time and, from this sum, subtracts the timestamp that is echoed by the remote TCP peer.