ITU-T Q.3313 PDF

This Recommendation provides the signalling format and procedures for the flow state aware (FSA) transfer capability in a bounded subnetwork of a next generation network (NGN). The FSA transfer capability provides QoS controls that operate on a per-flow basis, allowing flows within a bounded subnetwork of an NGN to receive different treatments depending on signalled parameters. These parameters are requested using in-band signalling. The parameters contained in these signals are included in the "flow state" maintained on each flow (or each aggregate flow), at each FSA node.

Out of scope are any FSA edge functions at the network domain boundaries needed for interworking between two FSA networks, where one uses in-band signalling exclusively for all FSA service support and the other uses both out-of band signalling (for resource reservation and clear down) and in-band signalling (to establish the agreed flow state). FSA signalling must not be used in the core network as it impacts on the scalability.