RE: [RRG] Will the flat ID and its corresponding resolution infrastracture be practicable? [RRG] Renumbering...

["Rolf Winter" <Rolf.Winter@nw.neclab.eu>]

Hi,

> Agree.  However, if the IDs are not allocated in any 
> hierarchy and they are randomly scattered across the DHT 
> overlay, the lookup speed will be decreased heavily. 

In general it has to be noted that in a DHT the number of lookup hops is a function of the number of nodes participating in the DHT not a function of the ID space.  

> Of 
> course, the tree-like mapping system like DNS or ALT has the 
> same issue. So no matter DNS like mapping system or DHT, to 
> make it scale better(in aspect of lookup speed) , the id 
> should be allocated in some geographically aggregatable 
> manner. Strict hierarchy is not flexible to support ID 
> roaming since it may require some renumbering work, while the 
> full flat structure is also not feasible. It's better to make 
> some tradeoff.

I am not sure I follow you here. A geographic allocation of IDs would increase the look-up speed, that is what you are saying right? What are the underlying assumptions of this? If look-ups have an inherent locality property maybe. That is, end-host communicate with higher probability with nodes that are geographically close AND the node that is responisble for the lookup is in the same geographic region AND the underlying network topology follows this geographic constraints ONLY then this statement it true. Considering a popular application such as BitTorrent which also opens many connections simulatneously (i.e. would trigger numberous lookups), my personal experience is that locality does not impact the peer choice an awful lot. To deal with non-locality today we employ caches and CDNs (that's at least partly why we do it). And I think in general it is safe to say that we will continue to do it. 

	Rolf



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