We consider the problem of flow coordination in distributed multimedia applications. Most transport-level protocols are designed to operate independently and lack mechanisms for sharing information with other flows and coordinating data transport in various ways. This limitation becomes problematic in distributed applications that employ numerous flows between two computing clusters sharing the same intermediary forwarding path across the Internet. In this article, we propose an open architecture that supports the sharing of network state information, peer flow information, and application-specific information. Called simply the coordination protocol (CP) , the scheme facilitates coordination of network resource usage across flows belonging to the same application, as well as aiding other types of coordination. The effectiveness of our approach is illustrated in the context of multistreaming in 3D tele-immersion where consistency of network information across flows both greatly improves frame transport synchrony and minimizes buffering delay.

We consider the problem of applying aggregate congestion control to a class of distributed multimedia applications known as Cluster-to-Cluster (C-to-C) applications. Flows in such an application share a common intermediary path that is the primary source of network delay and packet loss. Using the Coordination Protocol (CP) architecture, we show how aggregate congestion control can be achieved with the following properties: Almost any rate-based, single-flow congestion control algorithm may be applied to make aggregate C-to-C traffic congestion responsive. C-to-C applications may use multiple flow bandwidth shares and still exhibit correct aggregate congestion responsiveness. C-to-C applications may implement complex, application-specific adaptation schemes in which the behavior of individual flows is decoupled from the behavior of the congestion responsive aggregate flow. Bandwidth filtered loss detection (BFLD) is presented as a technique for making single-flow loss detection algorithms work when aggregate traffic uses multiple flowshares. The approach is evaluated using both ns2 simulation and an experimental implementation in Free BSD and Linux. Results demonstrate its success for a wide range of network conditions.

This paper looks at the problem of multi-streaming in 3D tele-immersion and describes how a protocol architecture called CP (for Coordination Protocol) can be used to coordinate video frame transport between application clusters. CP provides application endpoints with information about current network conditions, and an open architecture for implementing application-specific coordination schemes. The scheme described in this paper apportions available bandwidth among flows such that frame transport synchrony, important for 3D reconstruction performance, is significantly enhanced.

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We study the effects of RED on the performance of Web browsing with a novel aspect of our work being the use of a user-centric measure of performance: response time for HTTP request-response pairs. We empirically evaluate RED across a range of parameter settings and offered loads. Our results show that: (1) contrary to expectations, compared to an FIFO queue, RED has a minimal effect on HTTP response times for offered loads up to 90% of link capacity; (2) response times at loads in this range are not substantially affected by RED parameters; (3) between 90% and 100% load, RED can be carefully tuned to yield performance somewhat superior to FIFO, however, response times are quite sensitive to the actual RED parameter values selected; and (4) in such heavily congested networks, RED parameters that provide the best link utilization produce poorer response times. We conclude that for links carrying only Web traffic, RED queue management appears to provide no clear advantage over tail-drop FIFO for end-user response times.

We study the effects of RED on the performance of Web browsing with a novel aspect of our work being the use of a user-centric measure of performance - response time for HTTP request-response pairs. We empirically evaluate RED across a range of parameter settings and offered loads. Our results show that: (1) contrary to expectations, compared to a FIFO queue, RED has a minimal effect on HTTP response times for offered loads up to 90% of link ca?pacity, (2) response times at loads in this range are not substantially effected by RED pa?rameters, (3) between 90% and 100% load, RED can be carefully tuned to yield performance somewhat superior to FIFO, however, response times are quite sensitive to the actual RED pa?rameter values selected, and (4) in such heavily congested networks, RED parameters that provide the best link utilization produce poorer response times. We conclude that for links carrying only web traf?fic, RED queue management appears to provide no clear advantage over tail-drop FIFO for end-user response times.