ble bounds for either service. For example, if a particular service modifies a header that another service requires to function correctly, the conflict resolution system can restore the original value before invoking the second service. This needs to be tightly controlled however, and requires significant intelligence to identify which parameters are core to a service's operation. 8.3.3 Requirements Several requirements for the success of a service orchestration system can be identified: Should not require large modifications to existing architecture. Any enhance- ments to the core of the IMS network should not require large modifications to the existing architecture or to existing services. It should allow for back- wards compatibility with existing services, while providing a smooth transi- tion should developers wish to utilize additional functionality. Flexible enough to handle new services. As many services will be designed by a wide range of developers on an ongoing basis, the SCIM should be able to adapt to the addition of new services without requiring large amounts of maintenance. Service Orchestration in the IP Multimedia Subsystem Support existing control protocols. SIP is used extensively throughout the IMS as the control protocol, while Diameter is used to convey information in a more secure manner. As the SCIM will need to interface with the SCSCF as well as the AS it is necessary to support SIP. The SCIM will also need to pull information from the HSS and to access information stored in the user's pro- file. This information can be used to determine what services the end user is allowed to access, as well as the manner in which these services should be accessed. Intelligent conflict detection and resolution. Negative service interactions have been a problem in numerous network architectures, and the IMS is expected to exacerbate this situation by greatly increasing the number of services and developers. The SCIM should be able to make intelligent decisions based on external factors in addition to t