layered peer-to-peer streaming yi cui, klara nahrstedt department of computer science university of...
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Layered Peer-to-Peer Streaming
Yi Cui, Klara NahrstedtDepartment of Computer Science
University of Illinois at Urbana-ChampaignSource International Workshop on NOSSDAV’03, June, 2003
Outline
Problem addressingAsynchronousHeterogeneity
Layered peer-to-peer streaming solutionUnlimited number of supplying peersConstraint supplying peersLayered rate heterogeneity
Performance evaluation Conclusion
Problem addressing
AsynchronousUser request media data at different timeSolution: cache-and-relay approach
HeterogeneityRequest stream of different qualities due to
resource constraints such as network bandwidth
Solution: layer-encoded streaming approach
Problem addressing (cont.)
Layered peer-to-peer streaming
FeatureLimited inbound/outbound
bandwidth Goal
Maximize total qualities
Subject to
Qk: total receive layers of peer k
Ik: inbound bandwidth
Ok:outbound bandwidth
Hk:peers
Layered peer-to-peer streaming
lk: inbound bandwidth of Hk (# of layers) Ak: available layers at the cache of Hk
H0: server,
S = { H1, H2, …, HM } : set of hosts sorted by available layer number
i.e., A1≤ A2 ≤ … ≤ AM
Qkm: # of layers get from host m
Qk: streaming quality
Basic algorithm (cont.)
Basic algorithm
Available cache layers Outbound bandwidth
H1
H2
H3
H4
Hk
Get from server !
Allocate maximum # of layers for Hk
Enhanced algorithm
Ck: constraint on maximum # of supplying peers Qk*(M, Ck): optimal solution if Hk can only choose
Ck supplying peers from H1~HM
Qmax(Hm+1, …, HM):
best contributor in { Hm+1, …, HM } Maximize total receive data at Hk
DP implementation ─ O(CkM2)
Fault tolerance
Normal departureDue to user logout or quality degradationThe departure peer notifies Hk to reconfigure
FailDue to machine crash or network failureEither temporally request from server
or suffer from quality degradation
Fault tolerance (cont.)
Available cache layers Outbound bandwidth
H1
H2
H3
H4
Hk Access from server or degradation !
Layered rate heterogeneity
Layer rate allocation schemesNatural Number Scheme
l0 = r0, rk = k r‧ 0
Exponential Scheme rk = r0 2‧ k
Fibonacci Scheme r1 = 2r0, rk = rk-1 + rk-2
Layered rate heterogeneity (cont.) ri: streaming rate of layer I (Kbps)
Ik, Ok: inbound and outbound bandwidth (Kbps)
Performance evaluation
40000 peersModem/ISDN: 50%, 112Kbps (max) Cable Modem/DSL: 35%, 1Mbps (max)Ethernet peers: 15%, 10Mbps (max)
60-min video, which consists of 50 layers, with full quality streaming rate = 1Mbps
Run 24 hours
Overall streaming quality and scalability Streaming quality satisfaction = Qk/Ik
Tradeoff between overall quality & constrained supplying peers
Fairness
Robustness
Layer rate heterogeneity
Conclusion
Introduce a layered peer-to-peer streaming approach to optimize the streaming quality of heterogeneous peers, save server bandwidth.
Hope to make best use of bandwidth resource of supplying peers.
Evaluate the solution by: Test fairness among peers according to streaming
quality satisfaction and bandwidth contribution. Test robustness against unexpected departures/fails.
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