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</b></span><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif;" class="">Klaus Schneider <<a href="mailto:klaus@cs.arizona.edu" class="">klaus@cs.arizona.edu</a>><br class="">
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</b></span><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif;" class=""><b class="">Re: [Ndn-interest] Issues in routing</b><br class="">
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<span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif; color:rgba(127, 127, 127, 1.0);" class=""><b class="">Date:
</b></span><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif;" class="">November 19, 2018 at 11:38:10 AM CST<br class="">
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</b></span><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif;" class="">Tanusree Chatterjee <<a href="mailto:tnsr.chatterjee@gmail.com" class="">tnsr.chatterjee@gmail.com</a>>,
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Hey Tanusree,<br class="">
<br class="">
I think it's useful to distinguish between 3 logical entities:<br class="">
<br class="">
1. Router -- forwards packets towards a storage location<br class="">
2. Content Store -- a temporary storage location (can be cleared at any time)<br class="">
3. Content Repository -- a permanent storage location (in the same sense as today's web servers are "permanent")<br class="">
<br class="">
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.<br class="">
<br class="">
Now to answer your questions:<br class="">
<br class="">
<blockquote type="cite" class="">So, if a router is down for some reason, what about the data it
<br class="">
<blockquote type="cite" class="">stores in its CS and the connections it hold?<br class="">
</blockquote>
</blockquote>
<br class="">
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.<br class="">
<br class="">
<blockquote type="cite" class="">If the router is <br class="">
<blockquote type="cite" class="">temporarily down, it can resume to its normal operations sometime later<br class="">
</blockquote>
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Sure. Why not?<br class="">
<br class="">
<blockquote type="cite" class="">But if the router is permanently down and there are several data
<br class="">
<blockquote type="cite" class="">it produce and there are no more copies of all the data.<br class="">
</blockquote>
</blockquote>
<br class="">
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).<br class="">
<br class="">
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.<br class="">
<br class="">
NDN, however, can help with the scalability: it reduces the load on the content repository when its content objects become more popular.<br class="">
<br class="">
<br class="">
Best regards,<br class="">
Klaus<br class="">
<br class="">
<br class="">
<br class="">
On 11/19/18 2:32 AM, Tanusree Chatterjee wrote:<br class="">
<blockquote type="cite" class="">Hello all,<br class="">
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?<br class="">
-- Thanks & Regards,<br class="">
Tanusree Chatterjee<br class="">
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