supporting vcr-like operations in derivative tree-based p2p streaming systems
DESCRIPTION
Supporting VCR-like Operations in Derivative Tree-Based P2P Streaming Systems. Tianyin Xu , Jianzhong Chen, Wenzhong Li, Sanglu Lu Nanjing University Yang Guo Corporate Research, Thompson Mounir Hamdi Hong Kong University of Science and Technology. Outline. Background - PowerPoint PPT PresentationTRANSCRIPT
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Supporting VCR-like Operations in Derivative Tree-Based P2P Streaming Systems
Tianyin Xu, Jianzhong Chen, Wenzhong Li, Sanglu Lu
Nanjing University
Yang GuoCorporate Research, Thompson
Mounir HamdiHong Kong University of Science and Technology
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Nanjing University Thomson HKUST
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Outline
Background P2P media streaming, interactive streaming, VCR-like operations;
Motivation
Solutions Derivative tree; System overview; VCR-like operation support.
Performance Evaluation
Conclusions
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Nanjing University Thomson HKUST
Background
P2P media streaming Everyone can be a content producer/provider. Cache-and-relay mechanism: peers actively cache media contents and
further relay them to other peers that are expecting them.
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* P2P live streaming is very successful!- CoolStreaming
(INFOCOM’05),- PPLive, Joost
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Nanjing University Thomson HKUST
Background
P2P interactive streaming is challenging!1. Allow different users to watch different portions of the video
• Affects the efficiency of coordinating content delivery
2. Support user VCR-like operations
VCR-like (Video Cassette Recorder) operations random seek, pause, fast forward/backward (FF/FB) For VCR-like operations, “jump” process is the most important.
• Most VCR-like operations can be implemented by “jump”.– random seek & pause: 1 jump; FF/FB: series of jump;
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Nanjing University Thomson HKUST
Motivation
Frequent VCR-like operations lead to peer churn. Peers dynamically (often frequently) leave their current positions
and “jump” to new playback positions.• May severely deteriorate users’ perceived video quality
- e.g., playback freezing, long response latency, even blackout
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Nanjing University Thomson HKUST
Motivation
Example of VCR Impact
Tree-based Overlay
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Source
Impacted Nodes
Perform VCR-like Operations
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Nanjing University Thomson HKUST
Motivation
Example of VCR Impact
Mesh-based Overlay
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Perform VCR-like OperationsSource
Impacted Nodes
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Nanjing University Thomson HKUST
Question: How to reduce VCR impact?
Intuition behind our idea• A well structured overlay• Departure of leaf node does not impact the system performance.• Departure of non-leaf node can recover quickly.
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Perform VCR-like Operations
Source
Perform VCR-like Operations
Traditional data delivery tree Derivative treeSource
Perform VCR-like Operations
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Nanjing University Thomson HKUST
Derivative Tree Basic concepts
Split line Overlapping ratio Derivative
Construction rule: For each node in the tree, if it is
root or a left child, it may have a number of right children and no more than one left child;
If it is a right child, it cannot have children any more.
Properties: (Theorem 1) The number of nodes in the tree
Data range of a derivative tree is:
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a
a
A
B
C
a
a
D
E
F
Split Line
Split Line
H
Data range
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Nanjing University Thomson HKUST
Derivative Tree
Derivative tree has the following features:
Supports asynchronous user requests by using an overlapping buffer design.
Be well structured and controllable. • Can trade off the network latency and message overhead by adjusting the overlapping
ratio and the height of the tree.
Provides low cost VCR-like operations and quick streaming service reconstruction.
Basic Operations Join Departure
10Dislab, NJU CS
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Node Join
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aS T U VWX Y ZRQPONMLK
a Video SegmentsI SRQPONMLKJ T U VWX Y ZHGFEDC …A B
aS T U VWX Y ZRQPONMLK
I RQPONMLKJHGFEDC
Case 1: join as a right child
I RQPONMLKJHGFEDC
a YaS T U VWX Y ZRQPONMLK
a Y
Theorem 3: Operation overhead: O(1)
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Node Join
12
aS T U VWX Y ZRQPONMLK
a Video SegmentsI SRQPONMLKJ T U VWX Y ZHGFEDC …A B
aS T U VWX Y ZRQPONMLK
I RQPONMLKJHGFEDC
Case 2: join in a left subtree
I RQPONMLKJHGFEDC
aS T U VWX Y ZRQPONMLK
aO
I JHGFEDCA B
Theorem 3: Operation overhead: O(2) (with central index in the root)
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Node Departure
13
aS T U VWX Y ZRQPONMLK
a Video SegmentsI SRQPONMLKJ T U VWX Y ZHGFEDC …A B
aS T U VWX Y ZRQPONMLK
I RQPONMLKJHGFEDC
I RQPONMLKJHGFEDC
I JHGFEDCA B
Case 1: leaf node leaving
A B
Theorem 4: Operation overhead: 0
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Node Departure
14
aS T U VWX Y ZRQPONMLK
a Video SegmentsI SRQPONMLKJ T U VWX Y ZHGFEDC …A B
aS T U VWX Y ZRQPONMLK
I RQPONMLKJHGFEDC
I RQPONMLKJHGFEDC
I JHGFEDCA B
Case 2: non-leaf node leaving (with right children)
A B
Theorem 4: Operation overhead: O(1)
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Node Departure
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aS T U VWX Y ZRQPONMLK
a Video SegmentsI SRQPONMLKJ T U VWX Y ZHGFEDC …A B
aS T U VWX Y ZRQPONMLK
I RQPONMLKJHGFEDC
I RQPONMLKJHGFEDC
I JHGFEDCA B
Case 3: non-leaf node leaving (without right children)
A B
Theorem 4: Operation overhead: O(H)
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Nanjing University Thomson HKUST
System Overview
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Three components
- Media servers · Simply provide media streaming
service (do not provide any VCR
function)
- Sessions · Formed as derivative trees
- SessionCircle · Connects the root nodes of all
sessions to form a DHT ring.
· Session discovery service (SDS)
is implemented for fast session
location.Theorem 5: It takes at most hops to locate the desired sessions using SDS, where is the number of sessions.
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Nanjing University Thomson HKUST
VCR-like Operation Support
The jump process caused by VCR-like operations: (Theorem 6)
• Case 1. Jump in the local session
=> Performs a departure and a join in the local session
overhead = 1 departure + 1 join
= T(leave) + T(join) =
• Case 2. Jump to another session
=> Performs a departure, followed by a SDS search operation, and then a
join operation to the new session.
overhead = 1 departure + 1 SDS search + 1 join
= T(leave) + T(SDS search) + T(join)
=
• Case 3. Jump nowhere
=> Departs the current session, and after a search failure, initiate a new session.
overhead = 1 departure + 1 SDS search
= T(leave) + T(SDS search) =
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Nanjing University Thomson HKUST
Simulation Settings
The simulation is built on top of a topology of 5000 peer nodes based on the transit-stub model generated by GT-ITM.
The default size of the playback buffer is 30Mbytes, i.e., each peer can cache 120 second recent stream.
The default overlapping ratio α of DT-based scheme is ½.
The arrival of peers follows the Poisson Process with λ = 5.
We compare some simulation results with RINDY(ICC’07) and DSL(TPDS’07).
• The three systems use similar buffer management (sliding buffer window) without setting dedicated disk storage.
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Nanjing University Thomson HKUST
Performance Evaluation
19Dislab, NJU CS
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Nanjing University Thomson HKUST
Performance Evaluation
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Nanjing University Thomson HKUST
Performance Evaluation
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Nanjing University Thomson HKUST
Performance Evaluation
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Nanjing University Thomson HKUST
Performance Evaluation
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Nanjing University Thomson HKUST
Performance Evaluation
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Nanjing University Thomson HKUST
Conclusions
We introduce Derivative Tree, a novel distributed overlay structure with inherent ability to organize dynamic and asynchronous peers while bring high resilience to peer churn. Thus, it effectively reduces the impact of dynamic node join and departure with low network overhead.
We propose VCR-like operation implementation in the P2P streaming system. The overhead of VCR-like operations is proved to be in O(log N)
The efficiency of the proposed scheme is confirmed using extensive simulations. The result show that our scheme outperforms the existing representative systems in terms of VCR impact.
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Nanjing University Thomson HKUST
26Dislab, NJU CS
The End