[Ndn-interest] Hop-by-Hop Flow Balance

Ravi Ravindran ravi.ravindran at gmail.com
Tue Mar 15 09:22:02 PDT 2016

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.


On Mon, Mar 14, 2016 at 4:09 PM, <Ignacio.Solis at parc.com> wrote:

> [ Disclaimer: CCN currently uses flow balance as well ]
> The current Hop-by-Hop Flow Balance is nonsense.
> On 3/10/16, 11:46 PM, "Ndn-interest on behalf of Alex Afanasyev" <
> ndn-interest-bounces at lists.cs.ucla.edu on behalf of aa at CS.UCLA.EDU> wrote:
> >[6] **Hop-by-Hop Flow Balance**:
> >    Over each link, one interest packet should bring back no more than
> one data packet.
> Seriously, who thinks this actually works?
> Let me quote the webpage (
> http://named-data.net/project/ndn-design-principles/ ):
> "[6] Hop-by-Hop Flow Balancing: Over each link, one interest packet should
> bring back no more than one data packet.
> 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.
> "
> Either there is a lot of information missing here to justify why this is
> so, or this is very naïve.
> 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.
> 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.
> Please explain why the 1-to-1 is good.
> 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?
> If this principle were to be re-written as:
> “Allow network nodes to participate in flow control” then the actual
> engineering solution might be able to achieve this.
> Finally, at least we should acknowledge the limitations this type of
> approach requires; like symmetrical forwarding.
> It would be awkward if the only way for NDN to work over Satellite links
> would be to break the principles.
> Nacho
> 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.
> --
> Nacho (Ignacio) Solis
> Protocol Architect
> Principal Scientist
> Palo Alto Research Center (PARC)
> +1(650)812-4458
> Ignacio.Solis at parc.com
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