schedules and overlays: interactions between information scheduling and topology management in p2p...
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Schedules and Overlays: Interactions Between Information Scheduling and Topology Management in P2P Streaming
Renato Lo CignoUniversity of Trento (UNITN)
Torino, 21th January 2011
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Agenda
Selecting peers and planning transfers: topology management or information scheduling?
Scheduling in structured systems: What is the freedom?
The NAPA-WINE architecture: a reprise An approach based on offer/trade protocol Analysis of Push based scheduling on quasi-
random topologies
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Structures or Swarms
Structured systems follow regular topologies Imply a (relatively) small number of contacts Restrict freedom in scheduling information Simplify scheduling choices (if any)
Swarms do not have a regular topology Large number of neighbors Reduced sensitivity to topology changes (churn) Multiple choices for information exchange Resilient but … can they perform?
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Structured systems: Scheduling follows topology Trees & Multi-Trees The burden or
performance is entirely on the tree maintenance algorithm
Non bandwidth-optimal (trees)
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Structured systems: Scheduling follows topology
Regular trees (and forests) Suffer from heterogeneity
Trees & Multi-Trees The burden or
performance is entirely on the tree maintenance algorithm
Non bandwidth-optimal (trees)
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Structured systems: Scheduling follows topology
Uneven/unbalanced treesare hard to manage/predict
Trees & Multi-Trees The burden or
performance is entirely on the tree maintenance algorithm
Non bandwidth-optimal (trees)
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Structured systems: Scheduling follows topology
Leaves do not contribute (trees)Multi-trees are hard to match
Trees & Multi-Trees The burden or
performance is entirely on the tree maintenance algorithm
Non bandwidth-optimal (trees)
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Structured systems: Scheduling follows topology Hypercubes Bandwidth-optimal in
homogeneous settings Minimum delivery delay when
bandwidth=stream rate What if nodes are not 2N ? What if resources are not
homogeneous? Even more complex than
trees to manage
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Unstructured systems:Scheduling decisions are required The information flow does not follow the
structure of the topology Peers have a neighborhood, not parents &
children ¿ What chunk to send / request ? ¿ To / From which peer ? ¿ When ?
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Unstructured systems:Random Topologies & Blind Selection Normally based on Pull
Blind Push is too wasteful Derived from file-sharing and BitTorrent
Choose neighbors at random (nearly/biased) Often following a selfish utility function
Search in neighborhood the information (chunks) more needed from the peers that gives them fast Bad Neighborhood?
Sorry, watch TV next time … or try to change it Inefficient Neighborhood?
The networks (and other peers) will suffer … who cares!
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Unstructured systems:Random Topologies & Blind Selection
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NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Unstructured systems: Beyond Random Pull Required functionalities
A Peer discovery protocol If good gives a random topology (may include a tracker)
A chunk exchange protocol Includes decisions on When / Who / What and Pull / Push
Additional (useful) functionalities A Topology Management protocol
Obtains topologies with given characteristics May make use of ALTO-like oracles
A robust, efficient, chunk/peer scheduler Must be coupled to the Topology Management Requires knowledge (signaling overhead) Can be Pull/Push or mixed
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Unstructured systems:Random Topologies & Useful Selection
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NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Unstructured systems:Random Topologies & Useful Selection
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Unstructured systems:Random Topologies & Useful Selection
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Unstructured systems:Random Topologies & Useful Selection
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
NAPA-WINE architecture
Scheduler layer
Overlay Layer
Active peers’InfoBase
Chunk buffer
PeerSelection
TradingLogic
Neighbourset
Topologycontroller
Peer-Rep
Net-Rep
Ext-Rep
REPcontroller
Video Source(s) Display(s)User Layer
ContentIngestion
Player ControlInterface
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Messaging Layer + NAT/FW traversal
Monitoring layer
MonitoringController
Pasv. meas Act. meas
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Monitoring layer
MonitoringController
Topology; Scheduling and Monitoring
Scheduler
Overlay Management
Active peers’InfoBase
Chunk buffer
PeerSelection
TradingLogic
Neighbor set
Topologycontroller
To/FromALTO
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Monitoring layer
A more abstract view
The T-Man offers a set of peers
The Scheduler feedbacks good ones / bad ones
T-Man offers more & merge based on feedbak
Neighbors
T-ManT-Man
SchedulerScheduler
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
NAPA-WINE architecture: Flexibility at Work Different implementations of
Topology Controller Peer Selection Trading Logic
Give rise to different architectures and interaction models of Topology Management and Scheduling Random Topology with Offer/Trade Random Topology with Deadline Based Chunk Push and
Earliest/Latest Peer selection (DLc/ELp … more later) ALTO-based Topology and Offer/Trade ...
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Random Topology and Offer Trade T-Man try to build a random graph with high
connectivity (Nn neighbors) The scheduler
Offers buffermaps with owned chunks to Np<<Nn peers
Answer FIFO to requests selecting chunks from the buffermao
Modify Np to keep a small stable queue of chunk transmissions
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
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Predictive trading
timeChunk #1 to Peer 2
Chunk #1 to Peer 5
Chunk #2to Peer 1
New Chunk Arrival
Receive SelectSend Offer
Chunk Transmission
Tdiff is the time between a new chunk arrival and the moment in which the tx queue becomes empty.
Toffer is the time between a new chunk arrival and the moment in which starts a new offer session.
Tqueue is the interval that runs from the reception of last select message until the moment in which the tx queue becomes empty.
Np is the number of neighbors that a peer contacts in every offer session.
Tdiff
Toffer Tqueue
Np
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
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The Adaptative Signaling Protocol Crucial parameters
Np should match peer upload capacity If Np is too small
Peers’ upload bandwidth is not exploited at best The transmission queue empties quickly Long periods of inactivity
If Np is too large Transmission queue becomes too long Large delivery delays and, possibly, losses A lot of signaling overhead is produced
Tdiff should match the minimum RTT among neighbors to avoid long idle periods (this means Toffer = Tqueue = 0)
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
[email protected] 2525
Comparison with fixed Np schemes
Chunk loss probability varying ρ.
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Offer/Trade scheduling
A form of Random Peer selection Bias towards peers that are closer & with more
bandwidth (faster to answer) Blind, or with explicit preference for peers with
higher upload (must be diffused with signaling) Chunk selection left to the destination
Selfish – does not take into account further distribution chances
Random Useful (results shown) or Latest Useful
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
More on Scheduling Lots of works done
Most ignore interaction with topology, assuming either full mesh or random with high connectivity
Most ignore difference between Pull (the receiver decides what to receive and from whom) Push (the sender decides what to send and to whom)
Explored in NAPA-WINE Push/Pull differences; Mixed schemes Chunk or Peer First strategies One distributed scheme, based on “Push, Chunk First”
has been proven optimal
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Scheduling Chunks and Peers Chunks
Random Useful (RU) Latest Useful (LU) – found fragile for pushing Earliest Useful (EU) DeadLine (DL), updated dynamically
Peers Random Useful (RU) Most Deprived (MD) Earliest Latest (EL)
DLc/ELp Proven Optimal
All can be combined with “network awareness” (bandwidth, delay, ...) thus interacting with and modifying the topology
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
DLc/ELp (push, chunk first) DLc: select the chunk i with the minimum deadline di
di = chunk emission time + T’ Ntx T’: any time larger than the chunk duration T Ntx: number of times this copy or the chunk has been
retransmitted by any peer Intuition: the smallest deadline identifies a chunk that is old
AND has not diffused in the system ELp: select the Peer which has the oldest most
recent chunk It is the peer which is distributing the oldest information Intuition: it is the peer that will be the first to start
distributing the chunk we give it
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
DLc/ELp (push, chunk first) Distributed, but requires buffermap diffusion Robust to small neighborhoods Sensitive to stale buffermaps
Confirmation before sending? OPTIMAL
Uniform scenario with bandwidth = streaming rate All peer receive all stream with delay td
td < log N + 1
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DLc/ELp: Worst case delay comparison
DLc/ELp and LUc/ELp are optimal, but ...
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
DLc/ELp: Worst case delay comparison
... LUc/ELp is fragile in face of neighborhood
reduction
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
More on Scheduling The goals we have are three
1. Minimize delays: Can we do better than offer/trade?
2. Minimize bandwidth wastes: No wrong decisions
3. Be Network-Aware: refine and optimize topology
DLδc/BAβELP δ is the postponing delay and can be used also
for priorities (embedded in chunks – see the presentation on QoS for that)
β is a weight for the bandwidth parameter
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Bandwidth-Aware ELp Algorithm
weighted combination Maximize:
t − L(Pj , t) + β (s(Pj)/s(Pi)) Where β is a weight assigned to the bandwidth
component L(Pj , t) is the expected arrival of the chunk to Pj,
through the bandwidth of the sender s(Pi)
Redistribution potential of Pj
through the bandwidth of the target peer s(Pj).
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
90th percentile as a function of heterogeneity with 3 classes of users
Bandwidth-Aware ELp Algorithm:Sample results
600 peers Nn 20
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Selected Literature (from NAPA-WINE)
C. Kiraly, R. Lo Cigno, and L. Abeni, “Deadline-based Differentiation in P2P Streaming,” in IEEE GLOBECOM 2010, Miami, Florida, USA, Dec. 2010
A. Carta, M. Mellia, M. Meo, and S. Traverso, “Efficient Uplink Bandwidth Utilization in P2P-TV Streaming Systems,” in IEEE GLOBECOM 2010, Miami, Florida, US), Dec. 2010
J. Seedorf, S. Niccolini, M. Stiemerling, E. Ferranti, and R. Winter, “Quantifying operational Cost-Savings through ALTO-Guidance for P2P Live Streaming,” in 3rd Workshop on Economic Traffic Management (ETM 2010), Sept. 2010
R. Fortuna, E. Leonardi, M. Mellia, M. Meo, and S. Traverso, “QoE in Pull Based P2P-TV Systems: Overlay Topology Design Tradeoffs,” in Proceedings of the 10th International Conference on Peer-to-Peer Computing 2010 (P2P'10), Delft, The Netherlands, August 2010
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Selected Literature (from NAPA-WINE)
A. Russo and R. Lo Cigno, “Delay-Aware Push/Pull Protocols for Live Video Streaming in P2P Systems,” in IEEE ICC 2010, Cape Town, South Africa, May 2010
L. Abeni, C. Kiraly, and R. Lo Cigno, “Robust Scheduling of Video Streams in Network-Aware P2P Applications,” in IEEE ICC 2010, Cape Town, South Africa, May 2010
C. Kiraly, L. Abeni, and R. Lo Cigno, “Effects of P2P Streaming on Video Quality,” in IEEE ICC 2010, Cape Town, South Africa, May 2010
A. Couto da Silva, E. Leonardi, M. Mellia, and M. Meo, “Chunk Distribution in Mesh-Based Large Scale P2P Streaming Systems: a Fluid Approach,” IEEE Transactions on Parallel and Distributed Systems, To appear
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Selected Literature (from NAPA-WINE)
R. Birke, E. Leonardi, M. Mellia, A. Bakay, T. Szemethy, C. K. amd R. Lo Cigno, F. Mathieu, L. Muscariello, S. Niccolini, J. Seedorf, and G. Tropea, “ Architecture of a Network-Aware P2P-TV Application: the NAPA-WINE Approach,” IEEE Communication Magazine, To appear
A. Couto da Silva, E. Leonardi, M. Mellia, and M. Meo, “Exploiting Heterogeneity in P2P Video Streaming,” IEEE Transactions on Computers, vol. To appear
F. Mathieu and D. Perino, “On resource aware algorithms in epidemic live streaming,” in 22nd International Teletraffic Congress (ITC22), Amsterdam, NL, 2010
M. Stiemerling and S. Kiesel, “A System for Peer-to-Peer Video Streaming in Resource Constrained Mobile Environments,” in CoNext U-NET Workshop, Rome, IT, Dec. 2009
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Selected Literature (from NAPA-WINE)
L. Abeni, C. Kiraly, and R. Lo Cigno, “Scheduling P2P Multimedia Streams: Can We Achieve Performance and Robustness?,” in IMSAA 2009, Bangalore, India, Dec. 2009
L. Abeni and A. Montresor, “Scheduling in P2P Streaming: from Algorithms to Protocols,” in IWSOS 2009, Zurich, CH, Dec. 2009
J. Seedorf, S. Kiesel, and M. Stiemerling, “Traffic Localization for P2P-Applications: The ALTO Approach,” in IEEE P2P 2009, Seattle, OR, USA, Sept. 2009
L. Abeni, C. Kiraly, and R. Lo Cigno, “SSSim: a Simple and Scalable Simulator for P2P Streaming Systems,” in 14th IEEE CAMAD, Pisa, Italy, June 2009
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
Selected Literature (from NAPA-WINE)
R. Lobb, A. P. Couto da Silva, E. Leonardi, M. Mellia, and M. Meo, “Adaptive Overlay Topology for Mesh-Based P2P-TV Systems,” in ACM NOSSDAV 2009, Williamsburg, VA, USA, June 2009
C. Kiraly and R. Lo Cigno, “On the Effects of Overlay Localization on P2P Networks,” in IEEE Infocom 2009 Student Workshop, Rio de Janeiro, BR, Apr. 2009
A. Russo and R. Lo Cigno, “Push/Pull Protocols for Streaming in P2P Systems,” in IEEE Infocom 2009 Student Workshop, Rio de Janeiro, BR, Apr. 2009
L. Abeni, C. Kiraly, and R. Lo Cigno, “On the Optimal Scheduling of Streaming Applications in Unstructured Meshes,” in IFIP Networking, Aachen, DE, May 2009
NAPA-WINE Final Workshop – Torino 20-21 Jan 20-21, 2011
THE END
Thank you!
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