[Ndn-interest] Regarding RTT for ndncatchunks in raspberry pi

Lan Wang (lanwang) lanwang at memphis.edu
Thu Jan 2 08:09:09 PST 2020

I assume the min RTT 4.777ms is closer to the actual RTT.   The RTT measurements from catchunks include the timeouts and retransmissions, so you can see the average and max are much larger.


On Dec 30, 2019, at 11:25 PM, Athreya Nagaraj <indiathreya92 at gmail.com<mailto:indiathreya92 at gmail.com>> wrote:

Hi Lan

Thank you for your response.

Please find below the output of ndncatchunks during one of the experiments-

All segments have been received.
Time elapsed: 55.1154 seconds
Segments received: 23832
Transferred size: 104858 kB
Goodput: 15.220085 Mbit/s
Congestion marks: 69 (caused 5 window decreases)
Timeouts: 414 (caused 5 window decreases)
Retransmitted segments: 347 (1.43513%), skipped: 67
RTT min/avg/max = 4.777/144.127/27253.940 ms

On Mon, Dec 30, 2019 at 11:50 PM Lan Wang (lanwang) <lanwang at memphis.edu<mailto:lanwang at memphis.edu>> wrote:
How did you measure the RTT during the catchunks transfer?  Maybe you can send the catchunks output (or at least part of it)?


On Dec 29, 2019, at 9:58 PM, Athreya Nagaraj via Ndn-interest <ndn-interest at lists.cs.ucla.edu<mailto:ndn-interest at lists.cs.ucla.edu>> wrote:

Hi all

I have used the term 'bus topology', which is wrong. The topology I have used is 4 raspberry pi devices connected via 3 point-to-point links in a linear fashion. I've attached a representative topology diagram. I apologize for my mistake.

Thanks and Regards
Athreya H N

On Sun, Dec 29, 2019 at 10:39 PM Athreya Nagaraj <indiathreya92 at gmail.com<mailto:indiathreya92 at gmail.com>> wrote:
Hi all

I'm a student working on a testbed of NDN. The testbed consists of four raspberry pi connected in a bus topology. The two end devices act as producers and consumers for NDN data. The middle two devices act as routers. I use ndncatchunks to send a 100 MB file through the testbed. I observe that the RTT for this is significantly more (around 10 times more) than that for an FTP application on the same testbed. The throughput is also lesser compared to FTP (around 20% lesser for NDN). I was wondering what could cause this difference.

Also, another observation I made was that when I was testing the testbed setup with ndnping, the RTT was not so high.

I have also previously worked on similar topology with NDN and the machines used were desktop machines. In this case, NDN was better than FTP.

Any thoughts on what could be causing this?

Thanks and Regards
Athreya H N
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