communications network including multicast services is described the module distributes the admission process between a centralized decision function and a distributed decision function in a fashion that solves admission control scaling problems the mechanism for interaction between the sac pdp and sac m is defined mechanisms are defined for the sac pdp to discover or learn the network capacity against which the admission control decisions will be made systems are also described for incorporating sac m in multicast replication points in the network allowing multicast replication points to participate in the admission control process application_number US 24628505 A description fig1 illustrates specific components of the session admission control system these include a sac m admission proxy node 1 this could be an external sac m or an application incorporating sac m functionality sac policy decision node 2 network capacity database 3 dimensioning learning function 4 discovery learning function 5 and an interface u2018 a u2019 designated by interfaces u2018 a 1 u2019 and u2018 a 2 u2019 the u2018 a u2019 interface is located between an application service requesting admission and the sac m node 1 or sac pdp policy decision node 2 which grants or denies that request the protocol for this interface is optionally based on sip session initiation protocol and uses extensions to its syntax for communication web services or other protocols may serve the same function there are two communicating entities the requester.