Re: [DNA] DNA BCP Submission

[JinHyeock Choi <jinchoe@gmail.com>]

Dear Sathya

> > "An RA with its current active prefix" can't represent a link
> > change
> > properly. Hence, it can't be a link identifier, unless a host
> > adopts CPL
> > technique. I am afraid we have a different notion about what link
> > identifier is.
> 
> Arrival of an RA validating the current active prefix or a timeout without such an arrival can not
> be used for link change identification? Please correct me if I am wrong here. The timeout value may
> be 3 time MaxRtrAdvInterval, but this should still
> work.

I agree that 'RA with current active prefix' can be used for link 
identity detection but kindly take notice an adverb 'PROPERLY'. 
That's why I wrote that it can't be a link identifier, NOT it can't 
do link identity detection. 

As I wrote before, we have a different notion about 'link identifier'.
We expect 'link identifier' to EXPLICITLY represent a link identity
and have the following two properties. 
1) When the same link identifer arrives, it means the same link.
2) When a different link identifer arrives, it means a different link.

If a host receives an RA with its current active prefix, it means it still 
remains at the same link. However, if a host receives 'an RA with 
a different prefix', it can't check for link change with it. 

In this framework, because current active prefix doesn't satisfy
2), it can't be a link identifier, though I agree that it can be used 
to check for link change. 

In CPL or LinkID (by Brett), a link change can be detected instantly, 
when a host get a different link identifier, such as the complete 
prefix list in CPL or LinkID option in LinkID.  
 
> > We wrote, in "DNA solution framework" draft,
> >
> >   ............................... Each link has its unique Link
> > Identifier and all
> >   routers in the link advertise the same Link Identifier in RAs.
> 
> I DISAGREE with the requirement of a 'unique link identifier' agreed among all the routers and the nodes in the link as the ONLY way to do this. The current active prefix in each node is also an acceptable identifier for the link even though it will not be the same in every node and every router. If a node can determine whether its current prefix is supported or not, it has determined link change - it may not be fast but it will still work. Again, I building this argument on my statement above - please correct me if I am wrong.

I guess this disagreement results from the disagreement on 
the link identifier definition. I wrote the above only to illuminate 
what I mean by the term 'link identifier', not to insist that is the
only way for link identity detection. 

We expect 'link identifier' to EXPLICITLY represent a link identity
and have the following two properties. 
1) When the same link identifer arrives, it means the same link.
2) When a different link identifer arrives, it means a different link.

To have the above properties, all the nodes adopting the same 
link identifier method, whether it be CPL or LinkID, should agree 
on the same, hence unique, link identifier. For example, if in a 
link, a node use CPL and the other use LinkID, then they may 
have different link identifers. However, among the nodes using CPL,
or any other link identifier, there can be only one link identifier
for a link. Otherwise 2) can't be satisfied.      

> > The main issue should be whether the draft deals with DNA
> > adequately
> > or not. If so, either way is ok for me about whether to include
> > other
> > stuffs or not. If not, the draft would better work on DNA proper,
> > instead
> > of payint too much attention on secondary stuffs.
> 
> Again, this is a very valid comment. With your input we will try to improve sections 4, 5  & 6 in -02.

ok. 

Thanks for your kind consideration.

Best Regards