[Nfd-dev] NDN Traceroute

[Dehart, John]

All:

After our recent discussions about ndn traceroute, I was tasked with
describing my view of what an ndn traceroute capability would be like.
I will try to find some time to review all the current and past traceroute
designs, but for now, this email will serve to keep the conversation going.

Keep in mind that I have not been involved in nfd development so
I won’t be getting in to the details of what all this means for nfd code.
Also, my terminology might not agree with the offical terminology.

My immediate goal is to understand how interests are routed in the NDN
Testbed at any given time. For example, I have a simple test that I have 
been running lately where I run 'ndnping /ndn/edu/ucla’ on the WU node 
and I see RTT’s bouncing around between 80ms and 1000ms
and at times ndnping timeouts. 

For me, an ideal first step for an ndn traceroute capability would
be to augment ndnping, ndnpingserver and nfd so that the ndnping interests
would be augmented at each forwarder with a tag for that node. Then
ndnpingserver could take those tags and return them in the data packet
sent back to ndnping. ndnping could then report the RTT and the path.

I understand that this would not test the possibility of finding application
data in a Content Store along the path. But for me, that is fine. I’m not
looking right now to test the intricate data flow of a multi-party application.
Perhaps there is a better way to collect and return the path data to
the source, something that would make it possible for a future version
to include Content Store hits.

I also believe that this will be an important tool for Jeff Burke’s group in the
application testing they are trying to do. It may not be 100% of what they
want and need, but I believe it will be a good start.

In working with Jeff and Peter on ndnrtc testing, I came across my WU to
UCLA ndnping test results.  Without an actual ndn-traceroute, I built my
own with the capabilities I have as manager of the NDN Testbed. I set the
US nodes up with nfd running in DEBUG, ran my ndnping test, collected
nfd log files and wrote some scripts to parse them and find the path that
my ndnpings were taking. Not exactly something that any user or app
developer could do. I could only do it because I have privileged access
to all the NDN Testbed nodes.

John