LOGO P2P & Multimedia Streaming NPUST-MINAR Professor : Sheau-Ru Tong Student : Yi-Chen Hsu 1

LOGO

P2P & Multimedia StreamingNPUST-MINAR

Professor : Sheau-Ru Tong Student : Yi-Chen Hsu

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Contents

Introduction1

P2P Network Streaming Architecture2

Stream Over P2P Neteork3

Issues In Multimedia P2P Streaming4

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1. Introduction

Introduction – 1.1

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A content delivery network or content distribution network (CDN) is a system of computers containing copies of data, placed at various points in a network so as to maximize bandwidth for access to the data from clients throughout the network. A client accesses a copy of the data near to the client, as opposed to all clients accessing the same central server, so as to avoid bottleneck near that server.

1. Content Delivery Net Work(CDN)

Content types include web objects, download-able objects (media files, software, documents), applications, real time media streams, and other components of internet delivery (DNS, routes, and database queries).

[Wikipedia]

YouTube is the most familiar solution for streaming video with client-server model over Internet


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IP-multicast-based techniques can efficiently share a single channel, but the server is only scoped at local networks.


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2. Streaming Proxy ServerIn computer networks, a proxy server is a server (a

computer system or an application program) that acts as an intermediary for requests from clients seeking resources from other servers. A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource, available from a different server. [Wikipedia]


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A caching proxy server accelerates service requests by retrieving content saved from a previous request made by the same client or even other clients. Caching proxies keep local copies of frequently requested resources, allowing large organizations to significantly reduce their upstream bandwidth usage and costs, while significantly increasing performance. [Wikipedia]


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Streaming Proxy Server Suffix-

Window Caching


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A peer-to-peer, commonly abbreviated to P2P, is any distributed network architecture composed of participants that make a portion of their resources (such as processing power, disk storage or network bandwidth) directly available to other network participants, without the need for central coordination instances (such as servers or stable hosts). Peers are both suppliers and consumers of resources, in contrast to the traditional client–server model where only servers supply, and clients consume.

[Wikipedia]

3. What is P2P?


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The Popular P2P ApplicationsP2P File System: open-after-downloading

• BitTorrent• BitComet • eDonkey• eMule

P2P Media Streaming System: play-while-downloading• KKBOX• ezPeer• Skype• PPStream• PPLive

• FOXY• Freenet• KazaA• WinMX

• Winny

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BitTorrent (protocol)A user playing the role of file-provider makes a file available to the network. This first user's file is called a seed and its availability on the network allows other users, called peers, to connect and begin to download the seed file.

As new peers connect to the network and request the same file, their computer receives a different piece of the data from the seed.

Once multiple peers have multiple pieces of the seed, BitTorrent allows each to become a source for that portion of the file. [Wikipedia]


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BitTorrent (Measurements)

The number of downloaders increases exponentially in a short period of time after the torrent’s birth (the flash crowd period), and then decreases exponentially, but at a slower rate.

The number of seeds also increases exponentially at first, and then decreases exponentially at a slower rate.


FROM: Measurements, Analysis, and Modeling of BitTorrent-like Systems

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P2P IPTV (PPStream)


FROM: A Measurement Study of PPStream

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P2P IPTV (PPStream)


FROM: Study of PPStream Based on Measurement

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P2P IPTV MeasurementIntroduction – 3.4

2006 FIFA World Cup

PPStream seems to get the data from many peers at the same time and its peers seem to have long session duration.

PPLive seems to get the data from only a few peers at the same time but its peers have not a long session duration.

SOPcast download policy looks like PPLive policy.

TVants download policy seems to mix PPStream and SOPcast policies.

FROM: P2P IPTV Measurement: A Comparison Study

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2. P2P Network Streaming Architecture

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Overlay NetworkP2P Network Streaming Architecture – 1

Overlay network is a computer network which is built on top of another network.

Nodes in the overlay can be thought of as being connected by virtual or logical links, each of which corresponds to a path, perhaps through many physical links, in the underlying network.

For example, distributed systems such as cloud computing, peer-to-peer networks, and client-server applications are overlay networks because their nodes run on top of the Internet. [Wikipedia]

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ChallengesP2P Network Streaming Architecture – 2

Dynamic uptime• Peers don’t always stay online in the system.

• Requesting peers need to find new supplying peers to replace the failed ones.

Limited and dynamic peer bandwidth• Unlike powerful video servers, peers have limited bandwidth capacities.

• The available bandwidth of supplying peers might fluctuate unexpectedly.

FROM: Challenges and Approaches in Large-Scale P2P Media Streaming

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Locating supplying peersP2P Network Streaming Architecture – 3.1

Centralized directory• EX: PPStream, PPLive• The simplest and most commonly used method


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P2P Network Streaming Architecture – 3.2

Hierarchical overlay structure• Peers are organized into a hierarchical overlay structure such as an overlay tree.• The new client probes each peer in the list and finds out the most suitable peer Px .


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DHT-based approach• Each peer is assigned a peer ID by hashing its own IP address using a common known hash function.

• Each object is also associated with a key in the same space of peer IDs by hashing the object itself.

• The peer with an ID equal to the hashed key is responsible for storing the object’s location (or the actual object).


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EX: BitTorrent (Kademlia) Third generation peer-to-peer networks use Distributed hash tables(DHT) to look up files in the network.

Kademlia uses a "distance" calculation between two nodes. This distance is computed as the exclusive or of the two node IDs, taking the result as an integer number.

The node ID is typically a large random number that is chosen with the goal of being unique for a particular node (see GUID). It can and does happen that nodes from Germany and Australia are "neighbours"; they have chosen similar random node IDs.

A basic Kademlia network with 2n nodes will only take n steps (in the worst case) to find that node. [Wikipedia]


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EX ： P2P-over-SIPAdditionally, implement P2P using SIP messaging

P2P-SIPoverlay Alice

128.59.19.194

REGISTERINVITE alice

65a1fc

d13da3

d4213f

d462bad467c4

d471f1

d46a1c

Route(d46a1c)

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14

21

3238

58

47

10

24 30

54

38

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Use DHT in server farm

Use DHT for all clients - but some are resource limited

Use DHT among super-nodes

Hierarchy Dynamically adapt

servers

clients

1

10

24 30

54

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http://www.cs.columbia.edu/IRT/p2p-sip

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Gossip-basedDepth-first search (DFS) is an algorithm for traversing or

searching a tree, tree structure, or graph. One starts at the root (selecting some node as the root in the graph case) and explores as far as possible along each branch before backtracking

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3. Stream Over P2P Network

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1. Content delivery path maintenance

Stream Over P2P Network– 1.1

Tree-based multicast

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SplitStream: High-Bandwidth Multicast in CooperativeEnvironments

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Topology Optimization in Multi-Tree Based P2P Streaming System

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In PROMISE, we represent the segment goodness as a function of the loss rate and available bandwidth because these two metrics: (1) can be measured segment wise, and (2) are the most influential on the receiving rate, and hence on the quality. A segment with high available bandwidth and low loss is unlikely to introduce high jitter or long queuing delay.

PROMISE: PeertoPeer Media Streaming

2. Content delivery path selection


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CoolStreaming/DONet: A Data-Driven OverlayNetwork for Efficient Live Media Streaming

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Inbound/outbound

Local rarest first (LRF) scheduling

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Optimal scheduling

Optimizing the Throughput of Data-Driven Peer-to-Peer Streaming

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Optimizing the Throughput of Data-Driven Peer-to-Peer Streaming

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On Peer-to-Peer Media Streaming

Out-bound bandwidth

0.5

0.25

0.125

0.125

Buffer delay

Optimal media data assignment algorithm OTSp2p

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Optimal media data assignment algorithm OTSp2p

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Distributed differentiated admission control protocol DACp2p

Average waiting time

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Distributed differentiated admission control protocol DACp2p

Average waiting time

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R2: Random Push with Random Network Coding in Live Peer-to-Peer Streaming

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4. Issues In Multimedia P2P Streaming

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Appropriate video coding scheme

Issues In Multimedia P2P Streaming – 1

Directed acyclic dependency graph representation for a typical MPEG layered-encoded video sequence (one network packet per layer, with IPBPB

format).

Each packet pnPacket size sn

Decoding timestamp tdn

Weight wn

The successful decoding of one packet is contingent on the successful decoding of some other packets, called ancestors of pn.

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LOGO P2P & Multimedia Streaming NPUST-MINAR Professor : Sheau-Ru Tong Student : Yi-Chen Hsu 1