PeertoPeer Live Video Streaming on the Internet Issues, Existing Approaches, and Challenges - PowerPoint PPT Presentation

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PeertoPeer Live Video Streaming on the Internet Issues, Existing Approaches, and Challenges

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Title: PeertoPeer Live Video Streaming on the Internet Issues, Existing Approaches, and Challenges


1
Peer-to-Peer Live Video Streaming on the Internet
Issues, Existing Approaches, and Challenges
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2
Introduction (i)
  • Live video streaming is still a controversial
    issue, because it can play a best-effort and the
    ultimate realization of Internet service quality
    and customer satisfaction expectations.
  • Many challenges were identified and pursued in
    the design of video streaming systems, such
    packet loss, network congestion, stream
    synchronization, and lack of service guarantee.

3
Introduction (ii)
  • From the encoding perspective there were also
    many proposals on error-resilient codec in
    attempts to deal with packet loss using error
    concealment techniques.
  • There are two categories of proposals, one
    offering multicast at the native IP layer.
  • The other, called end system multicast, pushing
    multicast functionality to the edge of the
    network, that is, at the application level.

4
Introduction (iii)
  • Content distribution network (CDN) providers that
    strategically place a large number of video
    servers around the Internet.
  • End users to obtain streaming video from one of
    the nearby servers, thus reducing the end-to-end
    delay and overall network congestion.
  • Our study also revealed that multi-segment and
    multi-path routing can help to reduce the
    connection time while exhibiting little impact on
    video playback quality.

5
Introduction (iv)
  • One of the key features in a P2P system is that
    each node contributes resources including
    bandwidth, storage space , and the total system
    capacity can actually increase as more nodes join
    a system.
  • It overcame some of the fundamental limitations
    in classical IP multicast protocols

6
Introduction (v)
  • It demonstrated that an overlay architecture can
    be effectively constructed in the dynamic and
    heterogeneous Internet environment.
  • In this article, we examine the P2P streaming
    technology to determine what shapes the current
    system design and what are the limitations and
    challenges in the current systems.
  • Coolstreaming system, we provide observations on
    possible future development.

7
Multi-Rate Multicast (i)
  • The earlier Internet video streaming system was
    largely built on the IP multicast model.
  • The key innovation is to ensure simultaneous
    dissemination of packets to a set of destinations
    traversing each link only once without
    duplication.
  • There are primarily two issues within the IP
    multicast framework (Fig.1)
  • Heterogeneity in that each receiver differs in
    its computing capability and access bandwidth.
  • Dynamic in that video playback quality varies in
    the best-effort Internet.

8
Fig.1
9
Multi-Rate Multicast (ii)
  • IP multicast encountered the following problems
    in the deployment
  • Scalability in that there are potentially a large
    number of multi-cast groups that must be managed
    in a large network.
  • A requirement for coordination of dynamic
    spanning tree(s) construction at routers across
    different autonomous subnets.
  • Routers must maintain the state, which violates
    the principles and creates difficulty in the
    design of high-level functions

10
P2P File Distribution Protocols (i)
  • P2P applications describe a class of applications
    that take advantage of often untapped resources
    storage, cycles, and content such as file, audio,
    and video.
  • We examine the basic architecture in one of the
    most popular P2P file distribution protocols,
    BitTorrent or BT.

11
P2P File Distribution Protocols (ii)
  • BitTorrent consists of two major components, one
    is the creation of torrent files and the other is
    the mechanism associated with downloading files.
  • The torrent contains metadata about a file that
    must be shared and the host information.
  • BitTorrent protocol is used for actual file
    transmission. The group of peers sharing a
    particular torrent is usually referred to as a
    swarm.

12
P2P File Distribution Protocols (iii)
  • There are two issues associated with this the
    first is the order in which a client should
    request the chunks from a file.
  • The second issue is with whom a peer should send
    and receive the data.
  • There could be many incentive-based schemes with
    the objective of optimizing download and upload
    performance.

13
Application-Layer Multicast (i)
  • There have been many proposals in the framework
    of so called application-layer multicast or
    overlay multicast.
  • The construction of a multicast tree was
    performed using an overlay network, that is, a
    virtual topology over the unicast Internet.
  • This demonstrated the feasibility of implementing
    multicast functions at the end system while
    keeping the core functionality of the Internet
    intact.

14
Application-Layer Multicast (ii)
  • In Sripanidkulchai used a large set of traces to
    validate the following important requirements
  • Sufficient resources for an overlay network
    construction
  • Inherent stability
  • Can an potentially support large scale.
  • Rao et al. evaluated a multi-tree framework and
    proposed a contribution awareness index as the
    incentive to enable better contribution from peer
    nodes .

15
Application-Layer Multicast (iii)
  • In general, overlay multicast has not been
    adopted in real commercial systems.

16
Coolstreaming (i)
  • Coolstreaming is based on a data-centric design,
    in which the key novelty is that every peer node
    periodically exchanges its data availability
    information with a set of partners.
  • The fundamental advantage of such a data-centric
    approach is that it eliminates the requirement
    for constructing and maintaining any specific
    overlay network.

17
Coolstreaming (ii)
  • This also offers the following unique advantages
  • Easy to deploy
  • Efficient
  • Robust and resilient
  • Figure 2 depicts the system diagram. There are
    three basic modules in the CoolStreaming system
  • Membership manager, which helps peers to maintain
    a partial view of other overlay nodes.
  • Partnership manager, which establishes and
    maintain partnership with other peer nodes.
  • Scheduler, which is responsible for the
    transmission schedule of the video segment.

18
Fig.2
19
Coolstreaming (iii)
  • Membership Manager each node has a unique
    identifier, such as its IP address and maintains
    a membership cache (mCache)
  • In a basic node joining algorithm, a newly joined
    node first contacts the origin node.
  • It randomly selects a deputy node from its mCache
    and redirects the new node to the deputy.
  • The new node can obtain a list of partner
    candidates from the deputy and contacts these
    candidates to establish its partners in the
    overlay.

20
Coolstreaming (iv)
  • Partnership Management a video stream is divided
    into segments of a uniform length, and the
    availability of the segments in the buffer of a
    node can be represented by a buffer map (BM).

21
Coolstreaming (v)
  • Scheduler Given the BM of a node and its
    partners, a schedule is to be generated for
    fetching the expected segments from the partners.
  • The scheduling algorithm must meet two
    constraints the playback deadline for each
    segment and the heterogeneous streaming bandwidth
    required from the partners

22
  • There have been many studies on the overlay
    topology.
  • There are two primary measurements of interest
    one is the overlay efficiency, and the other is
    the stability.

23
Topology
  • From our experience with Coolstreaming, we
    present the following observations
  • On a small timescale, the data-centric approach
    does not seem to lead to any specific topology
    given the random assignment of peer partnership
  • On a large timescale, there is strong evidence
    that the overlay architecture converges to a
    tree-like topology, especially for each
    sub-stream.

24
Traffic Engineering And Scalablity (i)
  • P2P streaming applications gain popularity
    largely due to their cost-effectiveness and easy
    deployment.
  • Longer start-up time or channel-switching time.
    In a client and server system, the availability
    of servers ensures that a client can easily
    locate the service.
  • The P2P approach, however, relies on availability
    of peers and content given the dynamics of the
    system, it usually takes a longer time to locate
    the service in a P2P system.

25
Content Distribution Networks
  • Content distribution networks (CDN) strategically
    place a large number of servers around the
    Internet.
  • These collaboratively deliver content to end
    users transparently.
  • The existence of CDN might well complement P2P
    streaming in two ways
  • One major problem of current P2P streaming
    systems is that the content is retrieved from a
    random set of peer nodes in the network.

26
Content Distribution Networks
  • It is difficult for a P2P network to provide the
    same level of service guarantee comparable with
    that of an infrastructure-based network.

27
Conclusion
  • In this article, we provided an overview of the
    state-of-the-art P2P streaming technologies.
  • We summarized the main innovations in the
    Coolstreaming system and described the main
    challenges.
  • Our intuition is that for a large system, the
    combination of P2P and CDN might well be the
    solution.
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