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

[Teng Liang]

Hi Mahyuddin,

Here is an example on how self-learning forwarding works: a device joins a
local network and it wants to find data under prefix '/A'. Assuming that
this local network is not running any routing protocols, there exists no
routes for '/A'. Using self-learning forwarding, the device first floods an
Interest with name '/A/0' to the network. Once the Data packet is found, it
will be sent back along a single path. The Data packet carries a prefix
announcement for '/A', so that nodes along the path can set up a FIB entry
for '/A'. As a result, a route is set up between the device and data host;
then subsequent Interests can be sent along the single path.

For more details of self-learning, you can read the paper (
https://named-data.net/publications/on_broadcast-based_self-learning_ndn/).

On Tue, Nov 28, 2017 at 2:32 AM, Mahyuddin Husairi <mahyuddin at gmail.com>
 wrote:

> During flooding (discovery and announcement), is there any specific
> broadcast suppression technique applied?
> If more than one consumer doing content discovery (interest packet
> flooding) or more than one producer doing content name prefix announcement
> (data packet flooding) using blind flooding, it will lead to flooding
> overhead and probably lead to broadcast storm (
> https://en.wikipedia.org/wiki/Broadcast_radiation) on the local network.
> The only control mechanism that i found in the source code and nfd dev
> guide is interest suppression which are design for different purposes.
>

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.

Teng


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