[Ndn-interest] Issues in routing

[Klaus Schneider]

Hey Tanusree,

I think it's useful to distinguish between 3 logical entities:

1. Router -- forwards packets towards a storage location
2. Content Store -- a temporary storage location (can be cleared at any 
time)
3. Content Repository -- a permanent storage location (in the same sense 
as today's web servers are "permanent")

These can all be on the same machine or on a different machine. For 
example, a core NDN router will probably have a content store, but not a 
content repository.

Now to answer your questions:

> So, if a router is down for some reason, what about the data it 
>> stores in its CS and the connections it hold?

Well, the content store will be unreachable. There is usually no notion 
of a "connection" in NDN, so other routers should be able to fetch the 
data from somewhere else.

> If the router is 
>> temporarily down, it can resume to its normal operations sometime 
>> later

Sure. Why not?

> But if the router is permanently down and there are several data 
>> it produce and there are no more copies of all the data.

That only matters if the last content repository is down. In this case 
the data might become unavailable, if all the content stores have 
cleared the data as well (which they are free to do).

NDN does not have the goal to permanently replicate every content piece 
inside the network. The content provider is still responsible for 
keeping their content repository up and running, and likely wants to 
provide some redundancy here.

NDN, however, can help with the scalability: it reduces the load on the 
content repository when its content objects become more popular.


Best regards,
Klaus



On 11/19/18 2:32 AM, Tanusree Chatterjee wrote:
> Hello all,
> 
> In NDN the routers are the busiest and most responsible entity in the 
> network. So, if a router is down for some reason, what about the data it 
> stores in its CS and the connections it hold? If the router is 
> temporarily down, it can resume to its normal operations sometime 
> later.  But if the router is permanently down and there are several data 
> it produce and there are no more copies of all the data. Can there be 
> any network administrator which can have the copies of the data of a 
> router when it is down? If it is a high connectivity node, can network 
> administrator can play a vital roll to take care the connections of the 
> nodes?
> 
> -- Thanks & Regards,
> Tanusree Chatterjee
> 
> 
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