Application-layer networks (ALN) are software architectures that allow the provisioning of services requiring a huge amount of resources by connecting large numbers of individual computers, e.g. Grids and P2P-Networks. Self-organization, like proposed by the Autonomic Computing concept, might be the key to controlling these systems. The CATNET project evaluates a decentralized mechanism for resource allocation in ALN, based on the economic paradigm of the Catallaxy. The economic model is based on self-interested maximization of utility and self-interested cooperation between software agents, who buy and sell network services and resources to and from each other.