The Differentiated Services (DiffServ) architecture for the Internet implements a scalable mechanism for qualityof-service (QoS) provisioning. Bandwidth brokers represent the instances of the architecture, that automate the provisioning of a DiffServ service between network domains. Although several bandwidth broker implementations (e.g. [1]) have been proposed, the alternatives and trade-offs of the different viable approaches of inter-broker communication were not studied up to now. This paper presents the broker signaling trade-offs considered in the context of a DiffServ scenario used by the Swiss National Science Foundation project CATI [8], and it presents results gathered by simulations.