Re: Preserving established communications (was RE: about draft-nordmark-multi6-noid-00)

[Erik Nordmark <Erik.Nordmark@sun.com>]

> To some extent I wonder how much of this is really a multi6 problem. As 
> you point out, we will never know how long ULP will continue to try 
> before giving up. This might render ULP hints useless in that 
> particular case. We also don't know what failure detection is in use 
> for the ULPs. More, if there is also a rerouting event causing 
> distribution of bad news, and perhaps a new set of locators, or the 
> signaling to move to new locators, this might trigger a "race-like" 
> condition, depending in what order the priorities are set and in which 
> order they arrive where, and then actually making the case worse - no? 

I think it makes sense to look for potential destructive interference.
It might be that we have to restrict some mechanisms (such as ULP
retransmit hints) from affecting the destination locator and others
to affect the source locator, and perhaps also specify a preference
between the different hints (for instance, the source locator in a
received packet might be a stronger indication of what to use
in destination packets than the ULP suggesting to use a particular
destination locator, or it might be the other way around).

But these types of policy considerations for selecting locators is
independent of the actual rehoming mechanisms I think.


> Would it not be better to simply say that survivability and 
> "restoration" time is due to these X factors, they can be influenced by 
> this - but they are not an issue per se for the multi6 layer. They 
> might depend on ULP signaling, BGP convergence, etc. But that is 
> another issue.
> 
> Am I making my life to easy here?

Perhaps a bit; but the policies can be worked on separately from the
mechanisms and the policies can evolve at a different rate in the future.

  Erik