[ndnSIM] initial RTO value

[yao hu]

Hi Alex,

Thanks for explanation. I understand. But every intermediate router also
maintains the estimate of the RTT for each interface to retrieve data,
right? This RTT estimate is used in setting up a retry-timer. Then what
happens if the timer expires and the router does NOT receive a NACK? It
still does not retry alternative faces?

Regards,
huyao



2013/5/30 Alex Afanasyev <alexander.afanasyev at ucla.edu>

> Hi huyao,
>
> This RTO refers only to retry for end-user retransmission.  Intermediate
> nodes, at least in the currently implemented strategies in ndnSIM, don't
> retry alternative faces, unless they receive a retransmitted interest from
> the end-user (retransmitted interest = interest for which there is an
> existing PIT entry, and interest is received from the face, from which the
> node already received the interest for the same name before).
>
> ---
> Alex
>
> On May 29, 2013, at 7:38 AM, yao hu <huyao at goto.info.waseda.ac.jp> wrote:
>
> Hi Alex and Yaogong,
>
> Thanks for your both explanations. For my understanding, this RTO is used
> in setting up a retry-timer. But I am a little confused by the word "retry"
> in "retry-timer". This "retry" refers to the retransmission for end users
> for sure, but it also refers to the retry for intermediate nodes (retry
> other alternative faces than failed one)?
>
> Regards,
> huyao
>
>
>
> 2013/5/29 Alex Afanasyev <alexander.afanasyev at ucla.edu>
>
>> Hi Yaogong,
>>
>> Thanks for opening an issue and finding the problem!  I just incorporated
>> your commit that fixes the incorrect initialization of attributes.
>>
>> As of now, the initial RTO is 1 second, and later cannot become smaller
>> than the minimum, which is by default set to 200ms.
>>
>> ---
>> Alex
>>
>> On May 28, 2013, at 8:21 AM, Yaogong Wang <ywang15 at ncsu.edu> wrote:
>>
>> Hi Alex,
>>
>> I believe the initial RTO should not be 200ms. According to the code, RTO
>> is set to m_currentEstimatedRtt + 4 * m_variance bounded by minRto and
>> maxRto. By default, m_currentEstimatedRtt is initially set to 1s (
>> InitialEstimation) and m_variance to 0. Hence, the initial RTO should be
>> 1s which is within minRto=200ms and maxRto=200s.
>>
>> The current code does set initial RTO to 200ms due to a bug that sets
>> m_currentEstimatedRtt to 0 initially. I have reported the bug here:
>> https://github.com/NDN-Routing/ndnSIM/issues/40
>>
>> Thanks,
>> Yaogong
>>
>>
>> On Wed, May 22, 2013 at 4:40 PM, Alex Afanasyev <
>> alexander.afanasyev at ucla.edu> wrote:
>>
>>> Hi huyao,
>>>
>>> Yes. There is an initial RTO value and it is 200ms.  You can control
>>> this value by setting "ns3::ndn::RttEstimator::MinRTO" value.  ndnSIM uses
>>> a modified version of RTT estimator, originally in Internet module:
>>> https://github.com/NDN-Routing/ndnSIM/blob/master/utils/ndn-rtt-estimator.cc
>>> .
>>>
>>> --
>>> Alex
>>>
>>> On May 22, 2013, at 10:52 AM, yao hu <huyao0107 at gmail.com> wrote:
>>>
>>> Hi Alex,
>>>
>>> Is there a default initial RTO value for consumer node? RTO should be
>>> calculated based on the observed RTT samples, but how about the first
>>> Interest timeout for some reason? If there is a default initial value, is
>>> it 200ms?
>>>
>>> Thanks for your explanation~
>>>
>>> Regards,
>>> huyao
>>>
>>>
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>>
>>
>> --
>> ============================
>> Yaogong Wang, PhD Candidate
>> Department of Computer Science
>> North Carolina State University
>> http://www4.ncsu.edu/~ywang15/
>> ============================
>>
>>
>>
>
>
> --
> **************************************************
> 早稲田大学 基幹理工学研究科 情報理工学専攻
> 後藤滋樹研究室
> 胡 曜 (HU Yao)
> E-mail : huyao at goto.info.waseda.ac.jp
> **************************************************
>
>
>
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