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

Athreya Nagaraj indiathreya92 at gmail.com
Wed Jan 8 08:47:38 PST 2020


Hi

I'm not using fixed-size pipeline because it won't collect rtt information.
So I changed the cubic class such that if cwnd value goes over 15, it won't
increase further.

I'm using face type ethernet. I've pulled the latest code of ndn-cxx, NFD
and ndn-tools from git just a few days back and built it.

On Wed, 8 Jan 2020 at 9:50 PM, Davide Pesavento <davidepesa at gmail.com>
wrote:

> What do you mean by "limiting the value of interest pipeline"? Are you
> using the fixed-size pipeline with ndncatchunks?
>
> Also, what is the type of the face between the Pis? Ethernet or UDP?
> And what versions of ndn-tools and NFD are you using?
>
> Thanks,
> Davide
>
> On Wed, Jan 8, 2020 at 7:45 AM Athreya Nagaraj <indiathreya92 at gmail.com>
> wrote:
> >
> > Hello all
> >
> > I have got an update and another question on this topic. I have reduced
> the test-bed size to two RPis. one being the producer and the other being
> the consumer. I figured out that by limiting the value of interest pipeline
> to around 15, the RTT decreases substantially enough to match the
> performance of TCP (without reducing throughput). However, I'm curious as
> to why this might be happening and are there any changes I can do to the
> configuration to keep the interest pipeline value over 100 and still have
> the same performance.
> >
> > My wild guess about this might be due to the buffer size. So regarding
> this, I have a question. When the ndn-cxx library writes the segment to the
> NIC buffer, will it write the contents of the segment or does it store a
> pointer to it in the queue? It would be great if someone can point me
> towards where this is implemented in ndn-cxx library or NFD.
> >
> > Thanks in advance
> > Athreya H N
> >
> > On Thu, Jan 2, 2020 at 10:17 PM Athreya Nagaraj <indiathreya92 at gmail.com>
> wrote:
> >>
> >> No. I've not increased the interest lifetime. Is there any other
> possible cause of such a high max rtt value?
> >>
> >> On Thu, 2 Jan 2020 at 10:07 PM, Davide Pesavento <davidepesa at gmail.com>
> wrote:
> >>>
> >>> Actually, ndncatchunks does not take RTT measurements for
> >>> retransmitted segments. So a max RTT of more than 27 seconds looks
> >>> very suspicious to me, unless you also increased the Interest
> >>> lifetime.
> >>>
> >>> Davide
> >>>
> >>> On Thu, Jan 2, 2020 at 11:09 AM Lan Wang (lanwang) <
> lanwang at memphis.edu> wrote:
> >>> >
> >>> > 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.
> >>> >
> >>> > Lan
> >>> >
> >>> > On Dec 30, 2019, at 11:25 PM, Athreya Nagaraj <
> 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> wrote:
> >>> >>
> >>> >> How did you measure the RTT during the catchunks transfer?  Maybe
> you can send the catchunks output (or at least part of it)?
> >>> >>
> >>> >> Lan
> >>> >>
> >>> >> On Dec 29, 2019, at 9:58 PM, Athreya Nagaraj via Ndn-interest <
> 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> 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
> >>> >>
> >>> >> <Untitled
> Diagram.png>_______________________________________________
> >>> >> Ndn-interest mailing list
> >>> >> Ndn-interest at lists.cs.ucla.edu
> >>> >> http://www.lists.cs.ucla.edu/mailman/listinfo/ndn-interest
> >>> >>
> >>> >>
> >>> >
> >>> > _______________________________________________
> >>> > Ndn-interest mailing list
> >>> > Ndn-interest at lists.cs.ucla.edu
> >>> > http://www.lists.cs.ucla.edu/mailman/listinfo/ndn-interest
> >>
> >> --
> >> Regards,
> >> Athreya H N
>
-- 
Regards,
Athreya H N
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