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Network-supported Rate Control Mechanism for Multicast Streaming Media

This paper presents a sophisticated two-layered multicast rate control scheme for streaming media, integrating receiver-driven and network-supported methodologies. It highlights the challenges of existing receiver-driven approaches, particularly regarding congestion response and layer protection. The proposed Network-supported Layered Multicast scheme (NLM) uses routers for dynamic layer control based on bandwidth conditions, demonstrating improved session state consistency and rate adaptation. The performance of NLM is evaluated through simulations, showcasing its effectiveness in maintaining streaming quality under varying network conditions.

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Network-supported Rate Control Mechanism for Multicast Streaming Media

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  1. Network-supported Rate Control Mechanism for Multicast Streaming Media Kiyohide NAKAUCHI, Hiroyuki MORIKAWA, and Tomonori AOYAMA, School of Engineering, The University of Tokyo

  2. Outline • Tow layered multicast rate control scheme • Receiver-driven scheme (RLM) • Network-supported scheme • Network-supported layered multicast scheme(NLM) • Comparison

  3. Introduction • In general, rate control for layered multicast is classified into two classes • Receiver-driven scheme • Each receiver makes decisions to add or drop an enhancement layer • Network-supported scheme • Some of internal nodes such as routers or switches adopt priority dropping mechanism which drops lower priority packets belonging to a higher layer, and decide the number of received layers for each receiver

  4. Introduction(Cont.) • Receiver-driven scheme • Join-experiment • Upgrade the number of layer if no congestion occurs • Degrade the number of layer if congestion occurs • Congestion detection • Loss rate threshold

  5. Introduction (Cont.) • Drawbacks of receiver-driven scheme • No base layer protection • Receivers can’t respond to the congestion quickly because of both the delay for estimation network conditions and detecting congestion(estimation delay) and the delay for leaving a multicast group

  6. NLM Architecture • NLM system consists of a sender, receivers, and routers with rate control mechanisms. • Sender • A sender hierarchically encodes sending data of a session to several CBR streams, and sends all streams on a single multicast group • As routers and receivers cannot identify a layer from its multicast address, the number indicating a layer is filled in somewhere in a packet header

  7. NLM Architecture • Receiver • A receiver joins a single multicast session on which all the layers of the session are transmitted • Layered-Multicast –capable Router (LMR) • LMRS are strategically located at boundaries between the areas with rich bandwidth and those with poor bandwidth or at the points where congestion frequently occurs

  8. Overview of Network-supported Rate Control Session State Table oif: output interface Lcur(Ij, Si): the number of layers allowed to be transmitted for session Si at oif Ij Lmax(Si): the maximum number of layers allowed to be transmitted for session Si

  9. Overview of Network-supported Rate Control • Rate control for NLM consists of the following three key functions • Filtering: • A LMR decides which layer to filter based on the current bandwidth allocation or on the request from downstream LMRs • Signaling: • A LMR requests upstream ones to filter a needless layer or to transmit a layer without filtering

  10. Overview of Network-supported Rate Control • Session control: • LMRs keep consistency of session state tables with on another

  11. Overview of Filtering mechanism DROP ADD

  12. Overview of signaling protocol

  13. Filtering algorithm • A LMR conducts rate adaptation by filtering when it detects congestion occur or been solved at an oif • Whenever a LMR queues a packet at Ij, it calculates the current qlenj using both the current queue length( ) and previous qlenj as folllows

  14. In order to wait the effect of the DROP (ADD) to be reflected to qlenj and Lcur(Ij , Si ) > 1

  15. Signaling Protocol Oif(j) of this LMR received command DRPO_REQ(Si, L) Oif(j) of this LMR received command ADD_REQ(Si, L)

  16. Session control • The purpose of session control is to keep consistency of Lmax and Lcur among session state tables of LMRs and to keep correct PrevID • Consistency of session state tables enables a LMR to select the proper target layer of DROP or ADD

  17. Session control(Cont.) • A sender of Si periodically multicasts SESS(Si , L) at intervals of ss_intvl when the sender is transmitting L (L = Lcur(Ij, Si)) layers

  18. Extend mechanism • In NLM, a LMR changes add_intvl j adaptively to the network conditions in order to minimize the frequency of rate oscillation • A LMR changes add_intvl j according to the following algorithm • If a LMR detects that congestion occurs due to ADD conducted by the LMR at oif Ij, the LMR increases add_intvl j as follows: • Otherwise, the LMR decrease add_intvl j as follows: , >1, increase constant , <1, increase constant

  19. Extend mechanism(Cont.) • A LMR recognizes that ADD causes congestion when one of the following conditions is satisfied • The LMR detect congestion at Ij within detect_period • The LMR receives DROP_REQ(Si, Lcur(Ij, Si)) at Ij within detect_period (congestion at a downstream link) • The LMR does not receive SESS() after detect_period has passed since the last ADD (congestion at a upstream link)

  20. Simulations • Simulation parameters and topology The maximum number of layer : 5 The rate of each layer is CBR and 100, 100, 200, 400, 800[Kbps] from the base layer respectively

  21. S1 LMR1 LMR2 R1 Since B is not enough for 5 layers, LMR1 increases add_intvl jgradually up to add_intvl_max to decrease the frequency of rate oscillation Simulation results B = 1.5 Mbps

  22. S1 LMR1 LMR2 Joins session S1 Generate CBR cross traffic with 1.3 Mbps R1 Simulation results(Cont.) B = 1.6 Mbps

  23. S1 LMR1 LMR2 R1 Simulation results(Cont.) B = 1.7 Mbps Join S1 Join S2

  24. Simulation results(Cont.) B = 1.0*N [Mbps] Maximum Loss Rate (N)

  25. Conclusion • NLM can avoid packet losses on a lower layer and achieve fairness • Simulation results presented in this paper indicate that good responsiveness, fairness and stability of throughput of NLM compared with a receiver-driven scheme

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