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Songqing Chen, Bo Shen, Yong Yan, Sujoy Basu, and Xiaodong Zhang

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1 Songqing Chen, Bo Shen, Yong Yan, Sujoy Basu, and Xiaodong Zhang
SRB: Shared Running Buffers in Proxy to Exploit Memory Locality of Multiple Streaming Media Sessions Songqing Chen, Bo Shen, Yong Yan, Sujoy Basu, and Xiaodong Zhang IEEE Proceedings of the 24th International Conference on Distributed Computing Systems (ICDCS’04) July 13th, 2006 Seo, Dongmahn

2 Contents Introduction
Shared Running Buffers (SRB) Media Caching Algorithm Performance Evaluation Conclusion Presenter’s Opinion Media Service Team

3 Contents Introduction
Shared Running Buffers (SRB) Media Caching Algorithm Performance Evaluation Conclusion Presenter’s Opinion Media Service Team

4 Introduction Web content delivery network
Server-proxy-client system proxy reduce network load and end-to-end latency cache, static The delivery of streaming media content larger size continuous and timely delivery a lot of resources have to be reserved high bandwidth of disk and network Media Service Team

5 Related works Partial caching Dynamic caching of streaming data
cache either a prefix or segments of a media object in the disk storage of the proxy Dynamic caching of streaming data memory-based running buffer based caching tech. the fixed-sized running buffer caching fixed-sized buffer to cache media data fetched by the proxy hoping that subsequent requests could reuse the interval caching consider the arrival intervals of all request pairs The smaller intervals, the more requests with given memory Media Service Team

6 Related works (cont.) Above both
do NOT take consideration of user access patterns Media Service Team

7 Related works (cont.) Other related works patching algorithms
take advantage of the client-side storage resource the greedy patching patch to the existing complete stream the grace patching restarts a new complete stream at some appropriate points in time the optimal patching consider how to reuse the limited storage on the client side to receive as many data as possible while listening to as many channels as possible Media Service Team

8 Works of this paper propose Shared Running Buffers (SRB)
a new memory-based caching algorithm for streaming media objects based on user access patterns and the requested media objects different buffers are fully shared useful when requests are highly temporally localized efficiently reclaim the idle memory space efficient near-optimal buffer replacement at runtime when requests are terminated propose Patching SRB (PSRB) improves the performance of the media data delivery without the necessity of caching Media Service Team

9 Contents Shared Running Buffers (SRB) Media Caching Algorithm
Introduction Shared Running Buffers (SRB) Media Caching Algorithm Performance Evaluation Conclusion Presenter’s Opinion Media Service Team

10 SRB Media Caching Algorithm
SRB (Shared Running Buffer) Motivation the limits of current memory buffering approaches based caching algorithm for streaming media with the aim to maximize the memory utilization Media Service Team

11 SRB Related Concepts Concepts
Interval Series Average Request Arrival Interval (ARAI) three buffer states and three timing concepts Construction State & Start-Time Running State & Running-Distance Idle State & End-Time Media Service Team

12 SRB Algorithm working flow
If the latest running buffer of the object i is caching the prefix of the object i, the request will be served directly from all the existing running buffers of the object Otherwise If there is enough memory, a new running buffer of a predetermined size T is allocated If there is no enough memory, the SRB buffer replacement algorithm is called to either re-allocate an existing running buffer to the request or serve this request without caching Update the End-Times of all existing buffers of the object i Media Service Team

13 SRB Algorithm (cont.) SRB Buffer Lifecycle Management
Starting from the Construction State a three-state lifecycle management process Case 1 : in the Construction State. The proxy makes a decision at the end of T If ARAI = ∞, initial buffer enters the Idle State (case 3) immediately If In (waiting time) > ARAI, the initial buffer is shrunk If In ≤ ARAI, the initial buffer maintains the construction state and continues to grow buffer expansion is bounded by the available memory Media Service Team

14 SRB Algorithm (cont.) Case 2 : in the Running State. Case 3 : in the Idle State. When a buffer enters the Idle State, it is ready for reclamation. time span T (the initial buffer size) is determined buffer has upper bound and lower bound Media Service Team

15 SRB Algorithm (cont.) SRB Buffer Dynamic Reclamation
Two types of session termination the complete session termination If the resident buffer is the only running buffer for the media object, the resident buffer enters the idle state If the resident buffer is not only running buffer, the buffer enters the idle state and maintains its content until its End-Time the premature session termination If one request is served from the middle of it resident buffer, the resident buffer maintains its current state and the request get deleted from all its associated running buffers. If one request is served from the head of its resident buffer, the request is deleted from all of its associated running buffers. If one request is served at the tail of a running buffer, deleting the request from the request list of its resident buffer, if the request list is not empty, do nothing If the request is at the tail of the last running buffer, the buffer will be shrunk to the extent that previous R is the last request served from the buffer. Media Service Team

16 SRB Algorithm (cont.) SRB Buffer Replacement Policy
propose popularity based replacement policies for the SRB media caching algorithm basic idea ordering on-going streams according to their popularities calculated in a certain past time period if demanded object has a higher popularity that the least popular object, deallocated and re-allocated Media Service Team

17 Patching SRB (PSRB) Media Delivering Algorithm
SRB is extended to a PSRB for sharing of such sessions using more client-side storage to maximize the data sharing among concurrent sessions to minimize the server-to-proxy traffic Media Service Team

18 Contents Performance Evaluation Introduction
Shared Running Buffers (SRB) Media Caching Algorithm Performance Evaluation Conclusion Presenter’s Opinion Media Service Team

19 Performance Evaluation
event-driven simulator to model a proxy’s memory caching behavior Both synthetic workloads and a real workload from enterprise media server logs real workload as REAL HP Corporate Media Solutions April 1 to April 10, 2001 403 total objects unique object size accounts to 20G 9000 requests, run for seconds 83% requests only view the objects for less than 10 minutes 56% requests only view the objects for less than 10% Only about 10% requests view the whole objects Media Service Team

20 Evaluation Metrics the server traffic reduction HP workstation x4000
neither object hit ratio nor hit ratio measure the traffic between proxy and clients HP workstation x4000 with 1GHz CPU and 1GB memory running Linux Redhat 7.1 simulation a set of seven algorithms in three groups buffering schemes the running buffer caching and the interval caching patching algorithms the greedy patching, the grace patching and the optimal patching two shared running buffer algorithms proposed in this paper Media Service Team

21 Performance Results Media Service Team

22 Performance Results (cont.)
Media Service Team

23 Performance Results (cont.)
Media Service Team

24 Performance Results (cont.)
Media Service Team

25 Performance Results (cont.)
Media Service Team

26 Contents Conclusion Introduction
Shared Running Buffers (SRB) Media Caching Algorithm Performance Evaluation Conclusion Presenter’s Opinion Media Service Team

27 Conclusion propose two new algorithms for efficiently delivering streaming media objects Shared Running Buffers (SRB) caching algorithm to dynamically cache media objects in the proxy memory Patching SRB (PSRB) algorithm to enhance the memory utilization in the proxy show simulation results Media Service Team

28 Contents Presenter’s Opinion Introduction
Shared Running Buffers (SRB) Media Caching Algorithm Performance Evaluation Conclusion Presenter’s Opinion Media Service Team

29 Presenter’s Opinion in the paper How about to study
Server-Proxy-Client system model simulation VS implementation media data characteristics server topology How about to study adapt to VCR-like functions Fast Forward, Fast Rewind, Pause, Resume and so on Media Service Team

30 Thank you! Media Service Team


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