Re: [DNA] Issue 3: Remove Subsection 3.2 - Inadequacies in RAinformation

[JinHyeock Choi <jinchoe@samsung.com>]

Dear Brett

Thanks for your helpful feedback that clarified my thoughts.  

> > The paragraph is intended to present the limitation of prefix list based 
> > approach at current stage. It's not my intention to suggest prefix list 
> > based approach as the solution.  
> > 
> The previous paragraph already states that RAs don't necessarily carry a
> complete list of prefixes.  This paragraph seems out of place to me.

'Omission of prefix' is not the only limitation of prefix based approach. 
Moreover I found that 'the omission of prefix' is about not so much 
'detect link identity' as 'validate IP address'. So I incorporate the last 
two paragraphs to update the 3.2. as below. 

Kindly give your opinions. 

Best Regards

JinHyeock 

------------------------------------------------------------------------
3.2  Link identity detection with a single RA
 
Usually a host gets the information necessary for IP configuration from 
RA messages. Based on the current definition [ND], it's difficult for 
a host to check for link change upon a single RA reception. 

To detect link identity, a host may compare the informations in an RA, 
such as router address or prefixes, with the existing ones.
 
The host may use a router address to try to check for link change. 
The router address in the source address field of an RA is of link-local 
scope, however, so its uniqueness is not guaranteed outside of a link. 
If it happens that two different router interfaces on different links
have the same link-local address, the host can't detect that it has 
moved from one link to another by checking the router address in 
RA messages.

The set of all the global prefixes assigned to a link can represent 
a link identity. The host may compare the prefixes in an incoming 
RA with the currently stored ones. An unsolicited RA message, 
however, can omit some prefixes for convenience [4] and it's not 
easy for a host to attain and retain all the prefixes with certainty. 
Hence, neither the absence of a previously known prefix nor 
the presence of a previously unknown prefix in the RA guarantees 
that link change has occurred.