[Ndn-interest] Problem of PIT not aggregating Interests
shijunxiao at email.arizona.edu
Thu Apr 25 07:01:23 PDT 2019
Thanks for complete information and packet capture. This behavior is by
You are using the best-route v5 strategy. For this strategy, after
forwarding an Interest, if another Interest with same Name+CBP+MBF arrives,
it may choose to either retransmit or aggregate. As you see in the pcap,
the strategy has chosen to retransmit the Interest.
decides between retransmit and aggregate. It gives every PIT entry a
"suppression duration". If a subsequent Interest arrives within the
suppression interval, the decision is "aggregate"; if a subsequent Interest
arrives past the suppression interval, the decision is "retransmit". This
happens at PIT entry granularity. The configuration is: initial suppression
interval is 10 milliseconds, and it doubles every time the Interest is
retransmitted, up to 250ms.
As pcap shows, the first Interest arrived at 1556172304.931403000, the
second Interest arrived at 1556172304.949144000. The interval between these
two Interests is 16ms that is greater than the initial suppression
interval. Therefore, the strategy decides to retransmit.
I wish there's a way to change suppression settings via strategy
parameters, but there isn't. I've entered NFD Feature 4924
<https://redmine.named-data.net/issues/4924> to add this feature.
If you just want to see Interest aggregation in action, time your consumers
better so that the Interests arrive within 10ms of each other.
If it's a real problem affecting your application, you may "watch" this
feature on Redmine to get updates, or contribute code to that feature
following contribution guidelines.
On Thu, Apr 25, 2019 at 2:58 AM yjinking at mail.ustc.edu.cn <
yjinking at mail.ustc.edu.cn> wrote:
> Hi, Junxiao,
> Sorry, on previous email I only attached the pcap files when two Interests
> were issued from the same consumer node. Here are the the pcap files when
> two Interests were issued from two different consumer nodes.
> NFD is the original one. We only added some codes in forwarder.cpp to
> print some information on the screen.
>> On Mon, Apr 22, 2019, 22:16 yjinking at mail.ustc.edu.cn <
>> yjinking at mail.ustc.edu.cn> wrote:
>>> 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
>>> 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
>>> 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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