[Ndn-interest] Issues in routing
Klaus Schneider
klaus at cs.arizona.edu
Tue Nov 20 07:45:58 PST 2018
On 11/19/18 11:58 PM, Tanusree Chatterjee wrote:
> 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?
I would assume it behaves the same way as any other link-state routing.
Why should it be any different?
Best regards,
Klaus
>
> On Tue, Nov 20, 2018 at 3:03 AM Klaus Schneider <klaus at cs.arizona.edu
> <mailto: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
> <http://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>
> > <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>
> <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>
> > <mailto: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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