1march-04 proxy cache management for fine-grained scalable video streaming jiangchuan liu the...
Post on 18-Dec-2015
217 Views
Preview:
TRANSCRIPT
March-04 1
Proxy Cache Management for Fine-Grained Scalable Video Streaming
Jiangchuan LiuThe Chinese University of Hong Kong
Xiaowen Chu and Jianliang XuBaptist University of Hong Kong
Infocom’04, March 2003
March-04 2
Outline
Introduction and Motivations Problem Settings and Solutions Performance Evaluation and Comparison Conclusion and Future Work
March-04 3
Proxy
Proxy
Video Server
Backbone Network
Video Caching
Proxy caching
saving video objects at proxies close to clients
Temporal locality Geographical locality
March-04 4
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
March-04 5
Partial Caching Interval caching (Dan96, Tewari98…)
Prefix caching (Sen99, Jin02…)
Segment caching (Wu01, Miao02, Chae,Chen03…)
1 4 5 6 7 8 9 3 4 5 6 7 8 9
r1r2 r1r2
1 2
2 3
March-04 6
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
March-04 7
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)
March-04 8
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
March-04 9
Outline
Introduction and Motivations Problem Settings and Solutions Performance Evaluation and Comparison Conclusion and Future Work
March-04 10
System Model and Operations
FGSstream
(bi)
ClientRequest
(ci)
ProxyRequest
UncachedPortionFilter
VideoRepository
Video Server Video Proxy
Monitor
Fil
ter/
Ass
embl
er
ProxyManager
BackboneNetwork
Cache
t i mebase l ayer
Enh l ayer
rate
March-04 11
Model Parameters
L Length of the video, t sL L L= +
tL Length of the prefix
sL Length of the suffix
ETp Probability of early terminations
H Proxy cache size for the video
baser Base layer rate of the video
l Client request rate for the video
M Number of client classes
ip Probability that a client is in class i , 0ip >
ic Client bandwidth of class i
ib Streaming rate for a class i client ( base i ir b c£ £ )
ia Utility of a client in class i , /i i ib ca =
March-04 12
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
March-04 13
Problem(1): Solution
2-segment Exhaustive search
Multi-segment Access probability – segment/rate
March-04 14
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
max
, 1
MH i ii
U ph l a=
= å
,
. .st
/ 1base i ir c a£ £ , 1,2,...,i M=
,
1 1i i i ic ca a- - £ , 2,3,...,i M=
ˆHB Bh£
March-04 15
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
March-04 16
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
March-04 17
Outline
Introduction and Motivations Problem Settings and Solutions Performance Evaluation and Comparison Conclusion and Future Work
March-04 18
Sample Configuration
Client Multiple classes Uniform, skewed
Utility function Linear
2-segments: early termination Probability = 0.3 A conservative configuration !
March-04 19
Backbone Bandwidth Reduction
0
10
20
30
40
50
60
0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
Normalized Cache Size
Bac
kbon
e B
andw
idth
Red
uctio
n (%
)
Compared to MaxLen
Compared to MaxRate
MaxLen: length first MaxRate: rate first
March-04 20
Joint Optimal Caching & Utility Assignment
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
Normalized Backbone Bandwidth
Exp
ecte
d U
tility
CacheSize = 0.1
CacheSize = 0.3
CacheSize = 0.5
March-04 21
Results for Multiple Videos
0
3
6
9
12
15
0 0.2 0.4 0.6 0.8 1
Skew Factor
Util
ity Im
pro
vem
en
t (%
) x
Joint OptimalBand OptimalCache Optimal
Baseline uniform cache partition + proportional bandwidth partition
March-04 22
Scalable Video or Replicated Video?
Backbone bandwidth reduction with FGS
0
10
20
30
40
50
60
70
80
0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
Normalized Cache Size
Ba
ckb
on
e B
an
dw
idth
Re
du
ctio
n (
%)
UniformS-narrowS-wide
Optimal caching for replicated video 1D knapsack
March-04 23
Scalable Video or Transcoding ?
1
10
100
1000
10000
FGS
Filter
FGS
Assembler
SFD
Filter
FD-DC
Filter
RQ
Filter
Co
mp
uta
tion
Tim
e x
x (
μs/
fra
me
)
Given a frame interval of 30 ms, our PC can support about 300 concurrent filter/assembler operations
March-04 24
Outline
Introduction and Motivations System Description Problem Settings and Solutions Performance Evaluation and Comparison Conclusion and Future Work
March-04 25
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
March-04 26
Future Work
Utility functions Tradeoff: accuracy/speed
Multi-segments Fastforward, backward
Practical issues Error control Synchronization Signaling
March-04 27
Thanks
Q & A
March-04 28
Scalable Video or Replicated Video?
0
10
20
30
40
50
0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
Normalized Backbone Bandwidth
Util
ity I
mpr
ovem
ent
(%)
'
Cache Size = 0.1
Cache Size = 0.3
Cache Size = 0.5
Utility improvement with FGS
top related