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
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22. Performance Results (cont.)
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23. Performance Results (cont.)
Media Service Team

24. Performance Results (cont.)
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25. Performance Results (cont.)
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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