Re: [DNA] Prefix information for link identification in DNA

[JinHyeock Choi <jinchoe@gmail.com>]

Dear Bernard

> >There are certainly adhoc networks in which there is no router.   However,
> >detecting attachment to such a network is quite difficult, because nodes
> >may join and leave and therefore there is no L3 invariant.  That is why the
> >DNAv4 reachability test cannot be used to detect attachment to adhoc
> >networks, but rather adhoc attachment is concluded after failiure of all
> >other approaches (reachability test, DHCPv4, etc.)
>
> James Carlson has recently pointed out that there really is no intrinsic
> reason why DNA cannot be applied to networks without a router, and has
> proposed modifications to DNAv4 to allow this. James has proposed that DNA
> be able to use any peer that is known to be stable as an indicator of
> network attachment.  This could be a router, or it could be another device.
> About the only fundamental limitation is that "network anchor" probably
> shouldn't obtain its address dynamically.

DNA aims to ascertain the validity of its IP configuration for
Internet connectivity, such as valid IP address or default router. So,
when a host's IP configuration is no longer valid, it can quickly
perform proper procedures, such as getting CoA and sending BU, to
re-establish IP connectivity.

However, in case of a link without a router, I wonder what IP
configuration parameter a host need to  verify for Internet
connectivity. Also I have difficulty finding out what is the use of
DNA in such a link.

> >>I would also agree that there are situations in which a network cannot be
> >>named using one of its prefixes.  In DNAv4, a private network is not
> >>suitable for identification because it is not unique.
>
> Along these lines, James has also proposed that confirmation of a "network
> anchor" enable the plumbing of all network configurations relating to that
> anchor.  The result of this is that networks are not named using their
> prefixes;  they are named based on the IP address/MAC address of the network
> anchor.

The notion of 'network anchor' is not clear to me yet. However, if we
ssume routers are network anchors, it may cause trouble to name a
network based on IP/ MAC address of routers, in case there are
multiple routers in a link.

Right now, CPL propose to name a link/ network with 'the set of all
prefixes on the link'. Similarly, we may name a link/ network with
'the set of all routers/ network anchors on the link'.

But it's difficult to identify a router in IP layer because there may
not be a global IP address for a router (interface).

> It seems to me that James' comments apply equally to both DNAv4 and DNAv6
> and call into question some of the fundamental assumptions that have been
> made relating to DNA.

According to DNA goals, RFC 4235,

   Detecting Network Attachment (DNA) is the process by which a host
   collects the appropriate information and detects the identity of its
   currently attached link to ascertain the validity of its IP
   configuration.

Do you want to re-investigate the above?

Thanks in advance for your kind consideration.

Best Regards

JinHyeock