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

[Brett Pentland <brett.pentland@eng.monash.edu.au>]

Bernard Aboba wrote:
>> 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.

OK.

>>> 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.

They might not need to be named that way either.  If there's some way
to select the network anchor then that device might be able to select
an identifier that is used for naming.  That way if the network anchor
goes away and is replaced by another, the name needn't go away with it.

> 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.

Decoupling DNA from both routers and prefixes has some attractions; 
stability of naming and reliance on routers, for example.  I guess we
need to look at the cost, and perhaps more importantly how a scheme
based on these network anchors would interoperate with devices/links
that don't have any support for such a scheme.

Brett.