[Ndn-interest] Issues in routing

[Tanusree Chatterjee]

Thanks a lot Klaus. In my previous email what I meant by* If the router is
temporarily down, it can resume to its normal operations sometime later *is
when the router resumes, what about the LSAs it had before going down?  Of
course for access router has to re-establish the tunnel for further
operations.

On Tue, Nov 20, 2018 at 3:03 AM Klaus Schneider <klaus at cs.arizona.edu>
wrote:

> > The nfd connection states that after installing NFD in a client machine,
> >> we can specify the IP address and port number of the remote NFD, so
> that
> >> NDN packets get encapsulated into UDP or TCP packets and sent to the
> >> remote NFD. e.g. nfdc create udp4://192.0.2.1:6363
>
> You are talking about running NDN over IP tunnels (here, UDP tunnels).
> However, these tunnels only exist for point-to-point communication
> between routers to make NDN run over IP networks. They could easily be
> replaced by an Ethernet face (if there was a direct Layer 2 connection
> between two routers).
>
> When using the word connection in your earlier sense ("and the
> connections [a router] holds", "take care the connections of the nodes")
> I assumed you are talking about a transport layer connection as it
> exists in TCP between client and server.
>
> However, this transport layer connection does not exist in NDN. A router
> does not maintain any connection state, thus nothing dramatic happens to
> the packet flow after a router goes down. You will lose a number of
> Interests/Data packets that would have gone through the router, but
> these can quickly be retransmitted, and will find a different path to
> the repository (if it exists).
>
> > when a
> >> new ndn node wants to enter in an existing network and establish a
> >> connection with a node of the network, it does the above thing, isn't
> >> it?
>
> This is different from the idea of a transport-layer connection, as
> described above. If your node could have a wired Ethernet connection to
> an NDN router, this step wouldn't be necessary. You could just send
> Interests to that router without needing an IP address.
>
> Moreover, I don't think it's related to routers going down, unless you
> are talking about your access router. In this case, you will (of course)
> need to re-establish the tunnel to the access router after it comes back
> up.
>
>
>
> Best regards,
> Klaus
>
>
>
>
> On 11/19/18 2:15 PM, Tanusree Chatterjee wrote:
> > Hello Klaus,
> >
> > Thank you. It cleared my doubts to some extent. But, you said that there
> > is no notion of connection in NDN and I did not understand what does it
> > exactly mean.
> > The nfd connection states that after installing NFD in a client machine,
> > we can specify the IP address and port number of the remote NFD, so that
> > NDN packets get encapsulated into UDP or TCP packets and sent to the
> > remote NFD. e.g. nfdc create udp4://192.0.2.1:6363
> > <http://192.0.2.1:6363/>  states the client machine wants to establish
> a
> > connection with 192.0.2.1:6363 <http://192.0.2.1:6363/>. Also as
> > Junaxio's explained in my last email answer that NDN-FCH service tells
> > us the IP of the routers near by. However, here I am a bit confused why
> > there is no notion of a connection. As my previous question was when a
> > new ndn node wants to enter in an existing network and establish a
> > connection with a node of the network, it does the above thing, isn't
> > it? Please tell me if I understood anything wrong.
> >
> > Thanks & Regards,
> > Tanusree Chatterjee
> >
> > On Nov 19, 2018 11:08 PM, "Klaus Schneider" <klaus at cs.arizona.edu
> > <mailto:klaus at cs.arizona.edu>> wrote:
> >
> >     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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> >
>


-- 
Tanusree Chatterjee
M:9836337175
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