p2p Streaming Short Mcomp (1)

8/8/2019 p2p Streaming Short Mcomp (1)

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Dr. Sumi Helal & Dr. Choonhwa LeeComputer & Information Science & Engineering Department

University of Florida, Gainesville, FL 32611{helal, chl}@cise.ufl.edu


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Slide courtesy:Prof. Darshan Purandare at University of Central Florida, USADr. Meng ZHANG, Dyyno Inc., USA

Jan David Mol, Delft University of Technology, The Netherlands


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` Introduction` Video Streaming Approaches

IP MulticastContent Distribution Network

Application Layer MulticastPeer-to-Peer Swarming Protocol

` Noteworthy P2P Streaming SystemsBT-Based Protocols

CoolStreaming, GridMedia, PPLive` Mobile P2P Streaming


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P2P Protocols:` 1999: Napster, End System Multicast (ESM)` 2000: Gnutella, eDonkey

` 2001: Kazaa` 2002: eMule, BitTorrent` 2003: Skype` 2004: Coolstreaming, GridMedia, PPLive` 2005~: TVKoo, TVAnts, PPStream, SopCast,

` Next: VoD, IPTV, Gaming


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Internet video is ~1/4 of consumer Internet traffic not including P2PAll forms of video ~90%by 2012

TV, VoD, Internet, andP2P

Mobile data traffic willdouble every year fromnow though 2012


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` Large-scale video broadcast over InternetReal-time video streamingLarge numbers of viewersx AOL Live 8 broadcast peaked at 175,000 (July 2005)x CBS NCAA broadcast peaked at 268,000 (March 2006)x NFL Superbowl 2007 had 93 million viewers in the U.S.

(Nielsen Media Research)

Very high data ratex TV quality video encoded with MPEG-4 would require 1.5Tbps aggregate capacity for 100 million viewers


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` I lti t` t t i tri ti t r

Expens i e

Akama i, ime li t, e t` App li a ti n aye r lti as t

Alte r na ti e t I lti as t

` P ee r-t -P ee r B ased

Sc a lab leNo se t p c os t

iab le


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` Network layer solution` Internet routers responsible for

multicasting

Group membership: remember groupmembers for each multicast sessionMulticast routing: route data tomembers

` Efficient bandwidth usageNetwork topology is best known innetwork layer


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` Per-group state in routersHigh complexity, especially in core routersScalability concernViolation of the end-to-end design principle:

c

statelessd

` Slow deploymentChanges at infrastructural levelIP multicast is often disabled in routers

`

Difficult to support higher layer functionalityE.g., error control, flow control, and congestion control


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` CDN nodes deployed at strategic locations` These nodes cooperate with each other to satisfy an

end users request` User request is forwarded to a nearest CDN node,

which has a cached copy` QoS improves, as end user receives best possible

connection`

Akamai, Limelight, etc

10


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Origin server (www.foo.com)

` distributes HTML` replaces:

http://www.foo.com/sports.ruth.gif

withhttp://www.cdn.com/www.foo.com/sports/ruth.gif

HTTP request for www.foo.com/sports/sports.html

DNS query for www.cdn.com

HTTP request for www.cdn.com/www.foo.com/sports/ruth.gif

1

2

3

origin server

CDNsauthoritative

DNS server

CDN server near client

client

CDN company (cdn.com)

` d istributes gif files` uses its authoritative

DNS server to routere d irect requests


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` Application layer solutionMulticast functionality in end systemsEnd systems participate in multicast via anoverlay structure

Overlay consists of application-layer links Application-layer link is a logical linkconsisting of one or more links inunderlying network

` Most ALM approaches form tree-based

topologyTree construction & maintenanceDisruption in the event of churn and nodefailures


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` Easy to deployNo change to network infrastructure

` Programmable end hosts

Overlay construction algorithms at end hosts can be easily applied Application-specific customizations

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` Data-driven/swarming protocolMedia content is broken down in smallpieces and disseminated in a swarmNeighbor nodes use a gossip protocol toexchange their buffer mapNodes trade unavailable pieces

` BitTorrent

` CoolStreamingPPLive, SopCast, Fiedian, and TVAnts are derivates of CoolStreamingProprietary and working philosophy not publishedReverse engineered and measurement studies released


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` Pull-based/mesh-basedRedundant chunk avoidance

` Robustness and simplicityData availability information rather than an explicit structure toguide data flow (i.e., no need for streaming tree construction)Periodical exchange of data availability with random partners andsubsequent retrieval of missing data (i.e., minimal impact fromupstream node failures)

` Higher overhead and longer streaming delayReal-time scheduling constraints (i.e., need for good peer andchunk selection algorithms)


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` Tree BasedContent flows from server to nodes along the treeNode failures affect a complete sub-treeLong recovery time

` Mesh BasedNodes maintain state information of neighbor nodesResilient to node failureHigh control overhead


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W hy Is P2P Streaming Hard?

` Real-time constraintsPieces needed in a sequential order and on time

` Bandwidth constraintsDownload speed >= video speed

` High user expectationsUsers spoiled with low start-up time and no/little loss

` High churn rateRobust network topology to minimize churn impact

` Fairness difficult to achieveHigh bandwidth peers have no incentive to contribute


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BT-Based P2P Streaming

` BitTorrento Meta data (.torrent file)o Download policy (piece selection: rarest first)o Upload policy (peer selection: Tit-for-tat)


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New Download Policy

` Request highest priority pieces` High prio: download in-order ` Mid/low prio: download rarest-first` Effect:

dl speed = video speed: peer stays in high priodl speed > video speed: peer is often in mid/low prio


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` BitTorrent adapted for video streaming` Changes to BitTorrents piece selection algorithm


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` Video file is chopped and disseminated in a swarm` Node upon arrival obtains a list of 40 peers from the

server ` Node contacts these peers to join the swarm` Every node has typically 4-8 neighbors, periodically

sharing its buffer map with them` Node exchanges missing chunks with its neighbors` Deployed in the Internet and highly successful


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` Membership Manager Maintains a list of members in the groupPeriodically generates membership messagesDistributes it using Scalable Gossip Membership Protocol (SGAM)

` Partnership Manager Partners are members that have expected data segmentsExchanges Buffer Map (BM) with partnersBuffer Map contains availability information of segments

` Scheduler

Determines which segment should be obtained from which partner Downloads segments from partners and uploads their wanted segments


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` Designed to support large-scale live video streamingover the Internet

` The first generation: Gridmedia IMesh-based multi-sender structureCombined with IP multicastFirst release: May 2004

` The second generation: Gridmedia IIUnstructured overlay

Push-pull streaming mechanismFirst release: Jan. 2005


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` Original GridMedia` Overlay construction

Peers self-organize into a richly connected random mesh

`

Video deliveryPeers periodically notifies its neighbor of what packets they holdin the current window of interestEach peer randomly chooses a neighbor to request missingpackets

If a packet does not arrive (i.e., timeout), it is repeatedlyrequested from a randomly selected neighbor until the packetslides out of the window


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` Pull-based protocol has trade-off betweencontrol overhead and delay

To minimize the delayx Node notifies its neighbors of packet arrivals immediatelyx Neighbors also request the packet immediatelyx large control overheadTo decrease the overheadx Node waits until a group of packets arrive before informing

its neighborsx Neighbors can also request a batch of packets at a timex considerable delay


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Pull mechanism as startupSuccessful pulls trigger packet pushes by the neighborsEvery node subscribes to pushing packets from the neighborsLost packets during the push interval are recovered by pullmechanism


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` n -sub streams: packets with sequence number s % n` Loop avoidance

For n -sub streams, there are n packets in a p acket grou pPacket p arty is composed of multiple packet groups.Push switching is determined by the pull results of the first packetgroup in a packet party


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` Data-driven P2P streaming` Gossip-based protocols

Peer management

Channel discovery

` Very popular P2P IPTV applicationOver 100,000 simultaneous viewers and 40,000 viewers dailyOver 200+ channelsW indows Media Video and Real Video format


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` Mobile video streamingRapid growth of mobile P2P communicationVideo streaming expected to rise to as high as 91% of the Internet traffic in 2014

` Mobile environmentIncrease of mobile and wireless peersUnsteady network connectionsBattery power Various video coding for mobile devicesFrequent node churnSecurity


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` Mobile node issuesUplink vs. downlink bandwidthBattery power Multiple interfacesGeo-targeting

` Other mobility considerationsProcessing power Link layer mobilityMobile IP & proxy mobile IPTracker mobility


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` Video proxy located at the edge of networks Adaptive video transcoding considering the network conditions and constraints of mobile users

` Distributed transcoding by fixed nodesSub-streams from multiple parents are assembledResilient to peer churns


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` Hierarchical overlayMultiple network interfaces access link vs. sharing linkPeer fetches a video thru cellular networks ( W AN) toshare it with others over local networks (LAN)

` Cooperative video streamingP2P-based application layer channel bonding inresource-constrained mobile environmentsSimilar, in spirit, to channel/link bundling technology at

link layer to efficiently leverage the combined capacity of all access links


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p2p Streaming Short Mcomp (1)