<div dir="ltr">Another primitive that is missing in NDN/CCN is the need to PUSH content, most of the IoT and social networking applications requires this primitive. Today the solutions include using the long-lived interests or polling mechanisms which are not desirable, so if once such primitive is introduced this also questions the per-hop flow control objective.<div><br></div><div>Regards,</div><div>Ravi</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Mar 14, 2016 at 4:09 PM, <span dir="ltr"><<a href="mailto:Ignacio.Solis@parc.com" target="_blank">Ignacio.Solis@parc.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">[ Disclaimer: CCN currently uses flow balance as well ]<br>
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The current Hop-by-Hop Flow Balance is nonsense.<br>
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On 3/10/16, 11:46 PM, "Ndn-interest on behalf of Alex Afanasyev" <<a href="mailto:ndn-interest-bounces@lists.cs.ucla.edu">ndn-interest-bounces@lists.cs.ucla.edu</a> on behalf of <a href="mailto:aa@CS.UCLA.EDU">aa@CS.UCLA.EDU</a>> wrote:<br>
>[6] **Hop-by-Hop Flow Balance**:<br>
> Over each link, one interest packet should bring back no more than one data packet.<br>
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Seriously, who thinks this actually works?<br>
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Let me quote the webpage ( <a href="http://named-data.net/project/ndn-design-principles/" rel="noreferrer" target="_blank">http://named-data.net/project/ndn-design-principles/</a> ):<br>
"[6] Hop-by-Hop Flow Balancing: Over each link, one interest packet should bring back no more than one data packet.<br>
Hop-by-hop flow balancing enables each node to control load over its links. By deciding to sending interest over a link, router commits bandwidth for the returned data. By limiting the number of interests sent, each router and client node in the network control how much data it will receive.<br>
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Either there is a lot of information missing here to justify why this is so, or this is very naïve.<br>
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First, if what you want to do is limit the number of content objects (or packets) returned, you don’t need to send one interest. _Specially_ for NDN, which has prefix matching, you could send one interest with a count number (10) and expect to receive 10 content objects back. There is no reason why I need to send 10 exact copies of the same interest. Even if the interests had small variations, why send 10? Why not send 1 + the 10 deltas? I guess it’s possible you may call that part of the “network adaptation layer”, who knows.<br>
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Also by requiring 1-to-1, you are always requiring an overhead (on the requester side) that is quite high. If you think of today’s type of networks, where a packet (internet sized) is around 1500 bytes, that means that even if we send interests of 30 bytes, we are incurring quite a bit of overhead in the upstream. This becomes considerable when doing high bandwidth video.<br>
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Please explain why the 1-to-1 is good.<br>
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Second, NDN allows very large packet sizes. So, when I send 1 interest, I don’t now if what I’m going to get back is 1 byte or 18 exabytes. How do routers use this information to control how much data they’re going to receive? Are they going to reserve 18 exabytes of traffic time?<br>
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If this principle were to be re-written as:<br>
“Allow network nodes to participate in flow control” then the actual engineering solution might be able to achieve this.<br>
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Finally, at least we should acknowledge the limitations this type of approach requires; like symmetrical forwarding.<br>
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It would be awkward if the only way for NDN to work over Satellite links would be to break the principles.<br>
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Nacho<br>
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PS. Yes, there are people in this community who have looked at other ways to do flow-balance and flow-control. Maybe we should be learning from those and not just claiming as principle what we do today because we don’t want it questioned.<br>
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--<br>
Nacho (Ignacio) Solis<br>
Protocol Architect<br>
Principal Scientist<br>
Palo Alto Research Center (PARC)<br>
+1(650)812-4458<br>
<a href="mailto:Ignacio.Solis@parc.com">Ignacio.Solis@parc.com</a><br>
<br>
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