[Ndn-interest] Question regarding consistency

[Wentao Shang]

> On Aug 24, 2015, at 6:12 AM, aniesh chawla <chawla.aniesh at gmail.com> wrote:
> 
> Hello Everyone,
> 
> I have a very basic doubt which I could not resolve while reading documentation of NDN. I would like to also take this as research topic if my doubt is valid.
> 
> The question is:
> How is the consistency of data maintained in the network? Since, NDN is "pull" based networking and lets say there is change in file version at one of the node and not in other nodes. I can see the this can be achieved through NDNFS, but still the other nodes will not have change in version of the file. So, how will the new node who is requesting for that file will get to know which version to ask for?

Hi Aniesh,

As Lixia said in her reply, NDN is a layer-3 protocol. While it moves some of the application layer functionalities into the network layer, it cannot solve every problem the application faces.

NDNFS is a piece of software that demonstrates the idea of integrating application data unit (i.e., file blocks) with network data unit (i.e., NDN data packets). It was originally designed to be a local file system without any remote replication. Therefore the data consistency issue was conveniently ignored.

If you need synchronization across multiple copies of the data, you may run your application on top of ChronoSync, which gives you some form of eventual consistency.

Best,
Wentao

> If we use NDNS to resolve every such query and we use time stamp as version then also it should be propagated throughout the network? I also see that Chrono-sync does something like this but it has waiting timer for propagation delays. So either NDNS is talking to every node in the whole network or some other way.
> 
> Is my understanding correct or am I missing something here?
> 
> Thanks a lot
> 
> Regards
> Aniesh
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