[Ndn-interest] Problem of PIT not aggregating Interests

Wed Apr 24 04:17:51 PDT 2019

Hi, Junxiao,
Thanks for your reply. Here are some information you mentioned.
Today, We added some codes in forwarder.cpp to print some information when Interests passing and reconfigure the Producer's execution time. We found,  two Interest packets with same name from one node will have the same Nonce, then forwarder will forward just one Interest. 
And two Interest packets with same name from two different nodes will have different Nonce. Then forwarder will forward both them and Producer responded twice. Unlikely the previous time, two consumers received the same Data, which is exactly what procurer first replied.

"Aggregation vs retransmission depends on exact timing". Does that mean the possibility of aggregation is quite low?

From: Junxiao Shi
Date: 2019-04-23 10:52
To: yjinking
CC: ndn-interest
Subject: Re: [Ndn-interest] Problem of PIT not aggregating Interests
Hi yjinking

Aggregation vs retransmission depends on exact timing.
Can you capture traffic on the forwarder node as a pcap file with tcpdump? I can have a look.
Also paste the output of 'nfdc status' and 'nfdc face' and 'nfdc strategy' commands.

Yours, Junxiao

On Mon, Apr 22, 2019, 22:16 yjinking at mail.ustc.edu.cn <yjinking at mail.ustc.edu.cn> wrote:

Hi,all:
We encountered a problem that PIT can not aggregate two Interest packets with same name from two different nodes, but it can aggregate two Interest packets with same name from one nodes. 
We run NFD on 4 physical nodes consisting "Y"-shape topology(central node is forwarder, one Producer, two Consumers). Then two experiment were conducted:

1. We run ./examples/producer on producer node. We extended Producer's execution time to 5 seconds when Producer receives Interest. Then two Interest packets with same name from two different nodes were issued nearly at the same time. After about 5 second and 10 second, two Consumers received their Data packets subsequently. And two Data packets' timestamp were different. Producer responded twice.  

2. In another experiment, all is same with the first experiment, except that we only use one consumer node. Two Interest packets with same name from one nodes were issued nearly at the same time. After about 5 seconds, the consumer node received 2 Data packets with same timestamp subsequently. Producer responded once. 

According to the process of NDN, the result of the first experiment is very strange. Why didn't PIT aggregate the second Interest? Does NFD build PIT for each face separately? or maybe is there anything wrong in our experiment?

Plus, how can I print the content of FIB/CS/PIT on real time? Does NFD provide any interfaces?

Thank you!

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