QWERTY9 et al,
I am well aware that it is in the ATCOs nature to climb aircraft - however it is in the ATCOs interest to control aircraft... if that means that traffic managers from one unit need to start imposing restrictions and telling offering units, then thats what should happen - thats part of what a good traffic manager should do.
Traffic managers form offering sectors then need to pass the message onto the tactical controllers and this needs to happen all the way down th eline - however there is other ways of doing this pre-tactically. It's not a difficult concept, however until ATCOs start to accept a bit of systemisation into their controlling, they are going to continue to continue to be 'overloaded'.
There are ways and means to ensure that specific routes or airlines or city pairs are presented to your sector in a specific manner - it can be done at unit level.
Personaly speaking, I think 'overload' is cried too often by some sectors, especially when upon checking the figures you discover that although they have one figure as a normal operating value, they often actually control 30% or 40% more traffic because they take it on i.e. if they worked the traffic they were meant to they would not be 'overloaded'.
Realistic figures are needed to run a sector correctly, then in conjunction with that aircraft should be controlled in accordance with their Flight Plan - that way aircraft enter the sectors that they are actually targetted for and that the traffic is counted in.
Traffic managers can only work on the figures they have to hand, which are based on flight plans - the FP is then targetetted to the appropriate sectors and the traffic count emerges from that - if controllers continually allow aircraft to differ wildly from their flight plan, then they cannot expect the traffic managers to protect them!