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FCS networks are presented with a new transport layer mechanism that, for transmitting multimedia, is markedly superior to transmission over UDP or TCP. SCTP's multistrearning provides an aggregation mechanism for transferring different objects belonging to the same logical application session; however, sharing the congestion state among the streams precludes efficient stream prioritization. We design an SCTP mechanism to provide the application with the service of being able to mark data such that different parts of a transfer (different streams) could be requested to receive preferential treatment from the network. The data flow within an association is divided into separate subassociation flows (SF), each SF having its own set of congestion control parameters. We implemented this design using an SCTP stack from Siemens. A number of experiments show that the streams marked with higher priority achieve much better throughput. We plan to investigate a layered congestion avoidance technique that uses state information from individual subflows to allow: dynamic addition of subflows without slow start; load balancing between paths and subflows; and using network state information to provide intelligent feedback to the application.