+------+                              +------+
|Client|                              |Server|
+------+                              +------+
   |=========UPDATE(Requested CPD)======>|
   |<============PROCESSING==============|
   |<=========OFFER(Updated CPD)=========|
   |=============PROCESSING=============>|
   |==========ACCEPT(Updated CPD)=======>|
   |<==========ACK(Updated CPD)==========|
   |                                     |