[Nfd-dev] Broadcast suppression in Self Learning Forwarding Strategy

[Mahyuddin Husairi]

Thanks for the clarification related to broadcast storm effect on self
learning NDN during content discovery. I'm thinking to put that issue as
part of my research.

On Fri, Dec 1, 2017 at 10:46 PM, Junxiao Shi <shijunxiao at email.arizona.edu>
wrote:

> Hi Mahyuddin
>
>
>> During flooding (discovery and announcement), is there any specific
>> broadcast suppression technique applied?
>>
> The only suppression is Interest aggregation that aggregates multiple
> Interests with same name, selectors, and forwarding hint.
>
> If more than one consumer doing content discovery (interest packet
>> flooding)
>>
> Interest aggregation is effective for this, if the consumers are sending
> Interests with same name, selectors, and forwarding hint. It cannot help if
> the consumers are asking for different content.
>
>
>> or more than one producer doing content name prefix announcement (data
>> packet flooding) using blind flooding
>>
> This does not happen in self-learning. Producer cannot flood Data packets
> without first receiving an Interest.
>
>
>> it will lead to flooding overhead and probably lead to broadcast storm (
>> https://en.wikipedia.org/wiki/Broadcast_radiation) on the local network.
>>
> Yes, if the Interests are asking for different content, and they are all
> sent before the path is learned.
>
>
> Teng's answer:
>
>> For the self-learning, only the first Interest will be flooded;
>> subsequent Interests and Data packets are sent along a single path. If a
>> flooded Interest reaches a node that has a matching FIB entry, the flooded
>> Interest will not be flooded anymore. If multiple consumers send Interests
>> with the same name, NFD will do Interest aggregation instead of sending
>> redundant Interests out (this is a generic mechanism, not self-learning
>> specific). Thus the self-learning will not lead to broadcast storm, but to
>> avoid it.
>>
> This answer is correct. Broadcast storm does not occur if (1) flooded
> Interests have same name, selectors, and forwarding hint; or, (2) flooded
> Interests do not arrive at the same time, in which case only the first few
> would be flooded, and others are quickly converted into non-discovery
> unicast Interests as soon as they hit a node that knows the path.
> However, this answer fails to point out that: broadcast storm could occur
> if multiple consumers, at the same time, are flooding Interests with
> different name, selectors, or forwarding hint.
>
> Yours, Junxiao
>



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