[Ndn-interest] Questions about broadcasting an interest

Laqin Fan (lfan1) lfan1 at memphis.edu
Thu Dec 15 10:58:49 PST 2016

Hi Marc,

Thank you for your response.
My understanding is there will be a Data object implosion problem when many other nodes have a Data to satisfy the interest. PIT entry can filter the multiple response, but it will be expensive. And data broadcast traffic will make router (in the LAN) run much slower.
And I also wanna know if NFD uses unicast or broadcast the response Data. ☺


From: Marc.Mosko at parc.com [mailto:Marc.Mosko at parc.com]
Sent: Thursday, December 15, 2016 1:56 AM
To: Laqin Fan (lfan1) <lfan1 at memphis.edu>
Cc: ndn-interest at lists.cs.ucla.edu
Subject: Re: [Ndn-interest] Questions about broadcasting an interest

Unless some extra mechanism is used, one could have a Data object implosion problem when many other systems have a Data to satisfy the interest.  The sender’s PIT will filter out multiple responses, but it is expensive network-wise.  I am not sure if NFD will unicast or broadcast the response Data.

The old CCNx 0.8 forwarder would apply a randomized delay before answering a broadcast and if it saw another response during that period, it would suppress its transmission.  This is like a gossip style suppression sometimes used in MANETs.  It does rely on the response Data being broadcast too so everyone else sees it.  In a high-speed LAN, using this kind of broadcast-broadcast communications is pretty inefficient as a large switch often runs much slower with broadcast traffic.  Over other styles of networks, like wifi, it might make sense, though one would lose RTS-CTS and ACKs, which introduces other problems.

Personally, I think broadcasts should be use sparingly, such as for initial discovery or to elect a cluster head, etc., and then use unicast.


On Dec 14, 2016, at 10:34 PM, Laqin Fan (lfan1) <lfan1 at memphis.edu<mailto:lfan1 at memphis.edu>> wrote:

Hello all,

I have questions about broadcasting an interest, if a consumer asks for content by broadcasting its interest over all available connectivity, any node hearing the interest and having the satisfied data will respond with a data packet, the consumer will receive the first data packet? and how? what about the others? And if there are two data packets arriving at the consumer at the same time, what happens?
Could anyone please make me clear? I really appreciate it.

Laqin Fan
Ndn-interest mailing list
Ndn-interest at lists.cs.ucla.edu<mailto:Ndn-interest at lists.cs.ucla.edu>

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