1 Threshold-Based Multicast for Continuous Media Delivery Lixin Gao, Member, IEEE, and Don Towsley, Fellow, IEEE IEEE TRANSACTION ON MULTIMEDIA

2 Outline INTRODUCTION INTRODUCTION THRESHOLD-BASED MULTICAST THRESHOLD-BASED MULTICAST OPTIMAL THRESHOLD OPTIMAL THRESHOLD SIMULATION STUDY SIMULATION STUDY CONCUSION CONCUSION

3 INTRODUCTION Four types of multicast approaches Four types of multicast approaches Server-initiated Server-initiated Broadcast video every t minutes Broadcast video every t minutes Server-initiated-with-prefetching (SIWP) Server-initiated-with-prefetching (SIWP) PB, PPB … PB, PPB … Client-initiated Client-initiated Similar to Batch Similar to Batch Client-initiated-with-prefetching (CIWP) Client-initiated-with-prefetching (CIWP) Similar to Patch Similar to Patch

4 Server-initiated No Prefetch No Prefetch guarantee a maximum service latency guarantee a maximum service latency Waiting time independent to the number of request Waiting time independent to the number of request With Prefetch (SIWP) With Prefetch (SIWP) reduce the server network-I/O resources required reduce the server network-I/O resources required Reduce the waiting time more Reduce the waiting time more Good for hot video Good for hot video

5 Client-initiated No Prefetch No Prefetch batching reduces demand for server network-I/O bandwidth, but it does so at the cost of introducing service latency and there is no maximum service latency guarantee batching reduces demand for server network-I/O bandwidth, but it does so at the cost of introducing service latency and there is no maximum service latency guarantee With Prefetch (CIWP) With Prefetch (CIWP) Save server network-I/O bandwidth Save server network-I/O bandwidth Reduce waiting time (in Client-initiated) Reduce waiting time (in Client-initiated) Good for cold and lukewarm video Good for cold and lukewarm video

6 THRESHOLD-BASED MULTICAST

7 Motivation The Server network-I/O bandwidth The Server network-I/O bandwidth Basic CIWP ： a linear function of the request rate Basic CIWP ： a linear function of the request rate threshold-based ： a linear function of the square root of the request rate threshold-based ： a linear function of the square root of the request rate a hybrid of CIWP and SIWP scheme a hybrid of CIWP and SIWP scheme Cold and lukewarm Video Hot Video

8 Video delivery system architecture Low Bandwidth And Reliable Complete video stream Partial video stream

9 Interaction among client, data server, scheduler MG c ： complete stream MG p ： partial stream VLength ： the number of packets that receive from partial channel

10 Client Algorithm

11 Server Scheduler Algorithm 1) Batch the request with a complete stream of video that is scheduled to start later. 1) Batch the request with a complete stream of video that is scheduled to start later. 2) Prefetch from an ongoing complete stream of video and batch a partial stream of video scheduled to start later by expanding the partial stream. 2) Prefetch from an ongoing complete stream of video and batch a partial stream of video scheduled to start later by expanding the partial stream. 3) Prefetch from an ongoing complete stream of video and schedule a partial stream of video at the earliest possible time. 3) Prefetch from an ongoing complete stream of video and schedule a partial stream of video at the earliest possible time. 4) Schedule a complete stream of video at the earliest time 4) Schedule a complete stream of video at the earliest time

12 1. Batch a complete stream 2. <threshold Prefetch a complete stream Batch a partial stream 3. <threshold Prefetch a complete stream Schedule a partial stream 4.schedule a complete stream

13 Data Server Algorithm

14 OPTIMAL THRESHOLD requests for video are generated by a Poisson process with mean interarrival time requests for video are generated by a Poisson process with mean interarrival time We Assume the buffer size is not a constraint We Assume the buffer size is not a constraint min{ B, L i -B } min{ B, L i -B } ： denote the time at which the system schedules a complete stream for video (renewal point) ： denote the time at which the system schedules a complete stream for video (renewal point)

15 OPTIMAL THRESHOLD t i-1 t i

16 OPTIMAL THRESHOLD : the average server bandwidth : the average server bandwidth Poisson process K ： the number of arrivals in T i

17 OPTIMAL THRESHOLD Minimizes the expression Other Case

18 Server bandwith versus request rate

19 SIMULATION STUDY

20 Expected waiting time versus number of server channels.

21 Expected waiting time versus buffer size

22 Expected waiting time versus request arrival rate Reduces the expected waiting time Reduces the expected waiting time over 4.5 min compared to FCFS batching over 4.5 min compared to FCFS batching over 3.3 min compared to the basic CIWP over 3.3 min compared to the basic CIWP Even when the request rate increases to 100 requests per minute, the expected waiting time is still less than 1 min in threshold-based multicast. Even when the request rate increases to 100 requests per minute, the expected waiting time is still less than 1 min in threshold-based multicast.

23 Conclusion This paper presents a novel multicast technique that significantly reduces the demand on the server network-I/O band- width This paper presents a novel multicast technique that significantly reduces the demand on the server network-I/O band- width Unlike existing CIWP schemes, threshold- based multi-cast uses a threshold to control the frequency that a complete video stream is multicasted Unlike existing CIWP schemes, threshold- based multi-cast uses a threshold to control the frequency that a complete video stream is multicasted