RTT Calculations at a Node

["Jeremy Ethridge" <jethridg@nortelnetworks.com>]

Hi,

I have added a Queue object to ns to handle scheduling packets in a
particular way.  I want to implement functionality that requires dynamically
calculating RTT times for a TCP flow passing through that node.  I cannot
make use of the TCP Agent's RTT data, since the node in question can be an
intermediate node in a data path, without a TCP Agent associated with it.  I
want to calculate the RTT between that node and the destination, ignoring
any previous nodes in the data path.

I would like to monitor sample TCP data packets and their corresponding ACKs
passing through the node.  However, I cannot do this with a Queue object,
since such an object is associated along a unidirectional link.  If my Queue
object is associated with a link in the sender-to-receiver direction, it
will see the data packets, but not the ACKs.

So, I'm not sure how to solve the problem of calculating a TCP flow's RTT
between a given node and the flow's destination.  If anyone has any
suggestions, the help would be appreciated greatly.

Thanks,
Jeremy Ethridge.