he pre-existing conditions contained within the SIP request. This will allow richer and more flexible services. Service access management. It should be possible for the service orchestration function to authorize or control the access between different enablers or service capabilities. Network policies should be used to prevent unauthor- ized access to particular services' capabilities. Only authenticated and autho- rized use of the network's services should be allowed, even between different services. Minimize session setup delay. The SCIM should take advantage of offline con- flict detection in order to reduce the processing time needed to establish ses- sions. It should not get involved in the signaling path unless it is necessary. For example, the SCIM should not be invoked for an ordinary voice call between two parties. 8.3.4 Existing Research The study concluded by the 3GPP proposed three categories of network architec- tures for Service Brokers (SBs). These are the centralized, distributed, and hybrid approaches. The centralized architecture has one Service Broker (SB) that commu- nicates with and controls multiple AS. In this approach, the SCSCF treats the SB as another AS. The SB can be integrated with the SCSCF or it can be a stand-alone entity. The interfaces between the SB, the SCSCF, and the AS are all SIP-based interfaces. The distributed approach contains multiple SBs that each communicate with a single AS (Figure 8.3). Here, the SB can be integrated into the AS or it can be a stand-alone entity. As in the previous architecture, the SCSCF treats the SB as an AS, and the interfaces between the SCSCF and AS are SIP based. The SCSCF needs to ensure that all the appropriate messages are passed in a chain from SB to SB, until they have all finished executing their services. With the hybrid approach, the number of SBs and their connections to the various AS are not defined as strictly. It is possible to have a SB that acts both as a centralized and distributed SB Service Delivery Platforms SIP AS SIP AS 