The Swiss Exchange system (SWX system) was the first stock exchange system in service to be fully computerised. For high availability, the trading system is built as a replicated service based on Isis. For portability reasons, the SWX team has considered basing the next version of the trading system on CORBA. Despite the numerous advantages of a CORBA based solution, it was necessary not only to meet the functionality requirements of the system, but also to evaluate the performance of the chosen middleware. This paper describes a model that simulates the communication behavior of the trading system on Iona's Orbix and OrbixTalk. We have evaluated this model in order to illustrate some of the performance limitations of this communication infrastructure. We have also studied the fault-tolerance of the system and found that a key aspect in such a system is the state transfer. We have extended our model to support different schemes for state transfer. Measurements have shown us the conditions under which a state transfer could be performed in the background, concurrently with the normal operations.