[ndnSIM] Missing HopCountTag in Data Packets

Alex Afanasyev aa at CS.UCLA.EDU
Wed Feb 8 20:21:15 PST 2017


FYI.  Susmit sent me his code and after a bit of deep debugging, I discovered that this problem was actually caused by a small bug in ndnSIM.  I just pushed a fix to our code review system and it should be merged as soon as all sanity checks passed.

--
Alex

> On Feb 8, 2017, at 11:59 AM, Susmit <susmit.shannigrahi at gmail.com> wrote:
> 
> Hi All,
> 
> I have an ndnSIM topology with one producer, multiple consumers and
> intermediate nodes.  I am trying to get the hop count for incoming
> data packets at the consumers.
> 
> Below are the code and the trace for a single Interest packet.
> I confirmed that I am getting data from a different node (node 64)
> than the consumer (node 54), so the reply is not from local
> cache/local producer.
> 
> This is my code  for consumer::onData
> 
> ________________________ Code  ______________________________________
> 
>    void
>    onData(const ndn::Interest& interest, const ndn::Data& data)
>    {
>        auto ID = ns3::Simulator::GetContext();
>        auto now = ns3::Simulator::Now().To(ns3::Time::S);
> 
>         int hopCount = 0;
>         auto hopCountTag = data.getTag<ndn::lp::HopCountTag>();
>         if (hopCountTag != nullptr) {
>            hopCount = *hopCountTag;
>            std::cout << "Hop count: " << *hopCountTag << std::endl;
>          }
>        else {
>            std::cout << "Packet tag doesn't exist for " <<
> data.getName() <<  std::endl;
>        }
>        std::cout << "Time: " << now << ",node:" << ID  <<  "
> Consumer:onData"   << ",Data Name "  << data.getName() << ",Hop Count
> " << hopCount << std::endl;
> 
>        ..............
>    }
> __________________________ Trace ____________________________________
> 
> 
> 
> 
> 1. Scheduling /cmip5/app/zg_Amon_EC-EARTH_rcp45_r6i1p1_200601-205012.nc/%00%00
> at node 54 at time 1446227878 nonce 1495198176
> 
> 2. Time: +1.44622787799999999995,node:54, Consumer:delayedInterest,
> Interest Name /cmip5/app/zg_Amon_EC-EARTH_rcp45_r6i1p1_200601-205012.nc/%00%00
> 
> 3. Time :+1.44635877299999999996 node:64, Producer::OnInterest,
> Received interest:
> /cmip5/app/zg_Amon_EC-EARTH_rcp45_r6i1p1_200601-205012.nc/%00%00 Nonce
> : 1495198176
> 
> 4. Packet tag doesn't exist for
> /cmip5/app/zg_Amon_EC-EARTH_rcp45_r6i1p1_200601-205012.nc/%00%00/1495198176
> 
> 5. Time: +1.57473100799999999997,node:54, Consumer:onData, Data Name
> /cmip5/app/zg_Amon_EC-EARTH_rcp45_r6i1p1_200601-205012.nc/%00%00/1495198176,Hop
> Count 0
> 
> 
> I am not sure if I am missing something.
> 
> Thanks for your help.
> 
> -- 
> Regards,
> Susmit.
> _______________________________________________
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> ndnSIM at lists.cs.ucla.edu
> http://www.lists.cs.ucla.edu/mailman/listinfo/ndnsim




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