[Nfd-dev] Redundant data transmissions on error-prone links

[Gusev, Peter]

Hi Philipp,

On related note - I used forward error correction in NDN-RTC and published redundant data under “_parity” namespace for every video frame. This is not related to the problem with Interests you described, but relates to lossy links and retransmission/redundant data trade off.

Thanks,

--
Peter Gusev

peter at remap.ucla.edu<mailto:peter at remap.ucla.edu>
+1 213 5872748
peetonn_ (skype)

Software Engineer/Programmer Analyst @ REMAP UCLA

Video streaming/ICN networks/Creative Development

On Nov 27, 2016, at 11:35 PM, Philipp Moll <philipp.moll at itec.aau.at<mailto:philipp.moll at itec.aau.at>> wrote:




Dear NDN Developers,

I’m currently thinking of methods for redundant data transmission for real-time applications. In the case of (some) real-time applications a retransmission of lost packets is not reasonable. Therefore I would like to investigate redundant data transmission over multiple links. I think this could be useful especially in wireless access networks with higher loss rates.

My idea is, to duplicate Interests and send them out over multiple faces (similar to Multicast). This duplication means, that the same Interest will also arrive over multiple faces on some hosts. In order to achieve a redundant data transmission, it is necessary that the Interest is registered in the PIT from all in-faces.

I recognized, that the design of the Interest processing pipeline only allows that one Interest arrives from one face. If it arrives from two or more faces, only the first is processed, the others are classified as looping Interests, what is disadvantageous for my intent.

I was thinking and testing a lot in order to understand this pipeline design, but I can’t see, why Interests with the same nonce are classified as looping if they arrive over different faces. In my opinion, a loop can only occur if two Interests with the same nonce arrive over the same face.

This behavior also brings disadvantages in other cases. Imagine two nodes are connected over two links, a low latency low-bandwidth link, and a high latency high-bandwidth link. If a forwarding strategy like Multicast is used, only the low bandwidth link would be used because the Interest is faster at the receiver at this link. The Interest which traveled over the high bandwidth link is classified as looping, which means that the high-bandwidth link is not used, even if there are congestions on the low-bandwidth link.

I would like to ask, if anyone can explain the reason for this pipeline design or could give me advices for implementing redundant data transmissions.

Best regards,

Philipp Moll

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