1March-04 Proxy Cache Management for Fine-Grained Scalable Video Streaming Jiangchuan Liu The Chinese University of Hong Kong Xiaowen Chu and Jianliang Xu Baptist University of Hong Kong Infocom’04, March 2003

2March-04 Outline Introduction and Motivations Problem Settings and Solutions Performance Evaluation and Comparison Conclusion and Future Work

3March-04 Video Caching Proxy caching saving video objects at proxies close to clients Temporal locality Geographical locality

4March-04 Unique Features Video objects vs. Web objects High data rate, yet adaptive Long playback duration ► Various interactions: ־random access ־early termination ► Huge volume ־one-hour MPEG-1, about 675 MB

5March-04 Partial Caching Interval caching (Dan96, Tewari98…) Prefix caching (Sen99, Jin02…) Segment caching (Wu01, Miao02, Chae,Chen03…) r1r1 r2r2 r1r1 r2r

6March-04 Common Assumptions Continuous playback No interactions or premature termination Homogeneous segment access rate Homogeneous clients Identical access bandwidth Time partitioning only Non-adaptive caching Non-scalable single-rate video

7March-04 Our Assumptions and Objectives Assumptions User interactivity: early terminations Heterogeneous client access bandwidths Vehicle Fine-Grained Scalable (FGS) video Objectives Rate adaptive caching and streaming Understanding the benefits (?) of FGS caching ־Vs. Replication (Hartanto02), Transcoding (Tang02)

8March-04 Related Work and Differences Video staging (Zhang00) Quality adaptation (Yu00, Rejaie00) Adaptation per user basis Replacement Prefetching Blocking performance (Kangasharju02) Admission control Homogeneous access rate Caching for VCR-operations (Fahmi01) cut-off rate

9March-04 Outline Introduction and Motivations Problem Settings and Solutions Performance Evaluation and Comparison Conclusion and Future Work

10March-04 System Model and Operations

11March-04 Model Parameters

12March-04 Problem(1): Caching Strategy Explore the rate adaptability of FGS in caching Problem: Given cache size and client utility level, which portion of an FGS video should be cached Objective Min transmission cost Difficulty: Heterogeneous bandwidth demands Non-uniform segment access rate A 2-D space: time and rate ־Greedy is not optimal

13March-04 Problem(1): Solution 2-segment Exhaustive search Multi-segment Access probability – segment/rate

14March-04 Problem (2): Utility Assignment Explore the rate adaptability of FGS in both caching and streaming Problem Given cache size and backbone bandwidth limits, jointly decide the caching strategy and utility assignment of each client. Objective Max expected client utility,,,,

15March-04 Problem(2): Iterative Solution Difficulty Utility assignment  optimal caching strategy (problem 1) Caching strategy  optimal utility assignment (dynamic programming) Iterative optimization 2-Segment – exhaustive search on cache partition

16March-04 Optimization for Multiple Objects Heterogeneity of objects Access rate Access bandwidth Client distribution Cache partitioning Backbone Bandwidth partitioning 2-D Knapsack Pseudo-polynomial partitioning algorithm

17March-04 Outline Introduction and Motivations Problem Settings and Solutions Performance Evaluation and Comparison Conclusion and Future Work

18March-04 Sample Configuration Client Multiple classes Uniform, skewed Utility function Linear 2-segments: early termination Probability = 0.3 A conservative configuration !

19March-04 Backbone Bandwidth Reduction MaxLen: length first MaxRate: rate first

20March-04 Joint Optimal Caching & Utility Assignment

21March-04 Results for Multiple Videos Baseline uniform cache partition + proportional bandwidth partition

22March-04 Scalable Video or Replicated Video? Backbone bandwidth reduction with FGS Optimal caching for replicated video 1D knapsack

23March-04 Scalable Video or Transcoding ? Given a frame interval of 30 ms, our PC can support about 300 concurrent filter/assembler operations

24March-04 Outline Introduction and Motivations System Description Problem Settings and Solutions Performance Evaluation and Comparison Conclusion and Future Work

25March-04 Conclusion FGS-based proxy caching Key problems Optimal caching strategy Optimal utility assignment Optimization for multiple videos Performance Evaluation Backbone bandwidth reduction Utility improvement Comparision ־FGS caching vs. Replication caching ־FGS filtering vs. Transcoding

26March-04 Future Work Utility functions Tradeoff: accuracy/speed Multi-segments Fastforward, backward Practical issues Error control Synchronization Signaling

27March-04 Thanks Q & A

28March-04 Scalable Video or Replicated Video? Utility improvement with FGS