RFC 2638 from the IETF defines the entity of the Bandwidth Broker (BB) in the framework of differentiated services (DiffServ).
Admission control is one of the main tasks that a Bandwidth Broker has to perform, in order to decide whether an incoming resource reservation request will be accepted or not.
The BB acts as a Policy Decision Point (PDP) in deciding whether to allow or reject a flow, whilst the edge routers acts as Policy Enforcement Points (PEPs) to police traffic (allowing and marking packets, or simply dropping them).
[2] AF provides a better-than-best-effort service, but is similar to best-effort traffic in that bursts and packet delay variation (PDV) are to be expected.
Bandwidth Brokers only need to establish relationships of limited trust with their peers in adjacent domains, unlike schemes that require the setting of flow specifications in routers throughout an end-to-end path.