[Nsi-wg] New state machine with two phase reserve and modify

[Henrik Thostrup Jensen]

On Wed, 4 Jul 2012, Chin Guok wrote:

> Actually the IDCP has a single phase reservation workflow.

I stand corrected.

> That is the reason why it explicitly only supports the chain model.

(going off topic here)

Mmm... I do not see why that should restrict it to chain model. Sure tree 
will be somewhat oppertunistic, but as long as one can cancel the 
connections I do not see thep roblem. Could you eloborate?


Anyway, my point was that we should be careful about trading a simpler 
model for a more complex one in order to gain potentially better fault 
handling. 2PC has problems as well, the main ones being coordinator 
failures and added implementation complexity.

There is a middleground with oppertunistic methods (e.g., 3PC without the 
precommit - essentially pre-check + change without any blocking), which 
provide almost the same functionality but at a much lower implementation 
cost.

It feels a lot like we are using 2PC for the sake of using 2PC.


     Best regards, Henrik

  Henrik Thostrup Jensen <htj at nordu.net>
  Software Developer, NORDUnet