Each component, except Aries, whenever they are started notifies the other components about its presence. The only component that takes notice of it this is Hermes. Hermes, being the load balancer needs to know the whole set of network components.
The method by which the components find out about each other presence is by using Jini technology - mainly leveraging the multicast request protocol as described in Jini(TM) Architecture Specifications [22]. The method by which a component announces its presence is by locating the lookup services (which are native to Jini), download code to control the lookup service, use that code to register itself (and also upload its own code) and then periodically renew the registration. The code that is uploaded includes simple information that can be modified and queried - mainly the count of users, the maximum amount of users that can be handled, and the address of the system. This information is used in finding the load and availability of the system, which is explained in the next section.
All of these components: Hermes, Mors, Nemesis and Demeter are services (in Jini terminology), while Ares is the client. All the services are using Jini to announce their presence and find, if needed, the other components (Nemesis looks for Mors using Hermes' knowledge). Ares on the other hand, being a client doesn't announce its presence - it searches for the services it requires.