[ih] IP addresses are not phone numbers, was Some Questions over IPv4 Ownership

[Miles Fidelman]

Scott Brim wrote:
> On 10/17/2010 12:43 PDT, Miles Fidelman wrote:
>    
>> I guess I should also add the case of roaming, where one wants to
>> maintain TCP sessions while handing off link-level connectivity across
>> assets owned by multiple carriers.
>>      
> When multiple carriers are involved, why does the hand-off have to be at
> (so-called) link-level?
>    
Well... for current software to work right, maintaining a TCP connection 
requires that the underlying IP addresses remain the same (at least I 
think it does).  So somehow the IP numbers have to stay the same, while 
the underlying network connection changes.

It's not necessarily a link-layer function to do the handoff, but what 
is actually changing is happening at the link layer - one physical link 
is dropping, and a new one is coming up.

The hand-off is really a routing function - changing the mapping between 
a specific IP address and a specific physical link.  That shouldn't be 
too hard to do if one carrier is handing things from one asset to 
another, seems a bit more difficult when two carriers are involved - and 
brings us back to the original question of who "owns" the IP address 
when more than one carrier is involved. :-)

Miles



-- 
In theory, there is no difference between theory and practice.
In<fnord>  practice, there is.   .... Yogi Berra