Re: comments/questions on draft-yegin-dmm-ondemand-mobility-00

Hi Pete,

>>>> Alper,
>>>> 
>>>> I read the draft and have few quick comments and questions.
>>>> Interesting draft by the way. In Section 3.1. it says:
>>>> 
>>>> "- Access Network Anchored Address
>>>>  This type of IP address provides IP session continuity but not IP
>>>>  address reachability."
>>>> Why is that? What makes IP(v6) address unreachable (I assume from
>>>> Internet side)? I would like to see the rationale described here
>>>> for this reachability assertion.
>>>> 
>>> 
>>> 
>>> IP Address Reachability is defined as follows:
>>> 
>>>   IP address reachability: The ability to maintain the same IP address
>>>   for an extended period of time.  The IP address shall stay the same
>>>   across independent IP sessions, and even in the absence of any IP
>>>   session.  The IP address may be published in a long-term registry
>>>   (e.g., DNS), and it shall be available for serving incoming (e.g.,
>>>   TCP) connections.  IP address reachability is essential for mobile
>>>   hosts to use specific/published IP addresses.
>> 
>> 
>> I can read that from the draft but it still does not answer my question.
>> Say, I get an ANAA and the either the MN or the AN does dynamic DNS
>> update. Assuming the AN does not intentionally block incoming
>> connections for ANAAs the MN can be reachable. What is the rationale to
>> rule out incoming connections? I recon you also mix the "IP address
>> shall stay the same across independent IP sessions" with your definition
>> but IMHO that has very little to do with reachability.
> 
> I see Jouni's point, and I think the distinctions between different types
> of addresses and their capabilities is a bit artificial in both the Yegin
> draft and the prefix coloring approaches.
> 
> I think that any given address may change its type and function over its
> lifetime.  An address that was originally assigned as "Unanchored" could
> be promoted to "Access Network Anchored" if needed by the MN,

That's right.
But that's the only transition possible.

> and as Jouni
> notes an "Access Network Anchored" address could be registered in DNS to
> provide reachability, and then you just need to make sure you maintain
> that address for as long as the DNS entry exists + TTL.

It's a different type of reachability, with very distinct characteristic. Please see my response to Jouni.


>  A static coloring
> of prefixes at the time they are assigned is not good enough.  We really
> need to know how many references to an address are outstanding everywhere
> in the system, and garbage collect old addresses when these reference
> counts go to zero.  Of course, we cannot hope to keep track of all the
> places throughout the Internet that have cached a given IP address associated
> to an MN, but we can at least attempt to provide an approximation to this
> abstract idea.
> 
> Also, I take issue with the use of "anchored" to distinguish address types.
> It is possible for an address to be persistently assigned without being
> "anchored" on any one given endpoint, especially if we use routing instead
> of tunneling to maintain the connectivity.
> 

If one can propagate host routes across the Internet, then the anchor aspect disappears. 

Alper




> -Pete
> 
> 
>