network latency time

Hi,
I need to measure the latency time of a zigbee network. The network has an end node that sends data to the coordinator through three routers. I thought about making a software to send data to the end node through the uart, the end node then send this data to the coordinator that to send the data back to the end node.
My software records the time that the data was sent and the time it was received.
The problem is that I don’t know how to configure the endpoint to send the data received from the the uart and how to configure the coordinator to send the received data back to the endpoint.
I found this tutorial (http://www.digi.com/support/kbase/kbaseresultdetl.jsp?kb=188 ) in site of the digi, but it was made to xbee series 1. I am using xbee series 2.

Can someone help me?

This sounds like something you could do in a way similar to a range test. So, instead of sending a packet to an end node, then the end node sending a packet back, put a loopback plug in the end node and just measure the time it takes for the packet to be sent then echo back.

This article might give you some ideas:
http://www.digi.com/support/kbase/kbaseresultdetl.jsp?id=2194