PROMISE A Peer-to-Peer Media Streaming System Using CollectCast CPSC Presentation by Patrick Wong

Introduction PROMISE is a P2P media streaming system consisting of several different components. Different components of the PROMISE system include: 1.P2P Substrate 2.CollectCast: A P2P service forming the foundation of the PROMISE system. System was developed by Mohamed Hefeeda, Ahsan Habib, Boyan Botev, Dongyan Xu, Bharat Bhargava from Purdue University.

Peer-to-Peer Substrate P2P Substrate Maintains connectivity among peers. Manages peer membership. Performs object lookups. Examples include: Pastry Chord

CollectCast Architecture

PROMISE Operation Overview: Receiver Side 1.Receiver performs a lookup request to the P2P substrate, which returns a set of candidate peers. 2.An annotated topology of the available peers is created. 3.Using the topology, the best subset of peers is included into an active set. 4.The rest of the peers are kept in a standby set. 5.Receiver establishes two connections (one TCP and one UDP) with each peer in the active set. 6.Receiver determines sending rate and data assignment for each sender.

PROMISE Operation Overview: Switching & Sender Side Switching: If a peer failure occurs or the network becomes congested the active set is switched. During a switch topology is updated and a new active set is selected. Sender Side: Sender adjusts sending rate and retrieves data assignment from the receiver ’ s control packets.

CollectCast Architecture

Peer Selection Three peer selection techniques include: 1.Random Selection 2.End-to-End 3.Topology Aware

End-to-End Selection

Topology-Aware Selection

Topology Inference: Introduction Characterstics that are needed to determine the topology are: 1.Logical Topology 2.Available Bandwidth 3.Loss Rate Network Tomogrophy Technique Determining the interior characteristics of a network based on its end-points.

Topography Inference: Logical Topography During the Logical Topography Construction: All the links are discovered between the senders and receiver. A traceroute program is used by all peers in parallel to trace the route to the receiver in order to discover all the links.

Topology Inference: Available Bandwidth 1.One-way Delay Difference (Ddiff) is measured for a periodic packet stream. 2.If the streaming rate is higher than BW, Ddiff will show an increasing trend. 3.If streaming rate is lower than BW, Ddiff is 0. 4.Based on the trend of Ddiff, the stream rate will be increased or decreased by a factor of 2. 5.A single peer may not be able to send at a high enough rate. Multiple peers are used to simulate the effect of a single peer. 6.The probe data used to determine BW is the actual data itself.

Topology Inference: Loss Rate Lost packets are recorded at the same time as measuring the bandwidth (i.e the previous operation) Lost packets are only recorded on the end-to-end level. Probabilistic models are needed to infer individual segment losses.

Rate and Data Assignment Rate assignment refers to the streaming rate of the data and it is proportional to the offered rate of the peer. Data assignment refers to the number of packets that a peer needs to send to the receiver and it is proportional to the streaming rate. PROMISE uses a FEC mechanism to tolerate packet losses. Rate and data assignment are dependent on the loss tolerance of the FEC mechanism. As the loss tolerance is increased, the rate and data assignment are increased accordingly.

Monitoring and Adaptation Peer failure is detected using the following two indicators. 1.TCP control channel 2.Degraded rate. Failed peers are replaced with new ones from the standby set. All the remaining good peers are kept, which is a non-optimal solution.

PROMISE Evaluation 1.Simulation Experiments  1000 candidate peers and 600 routers.  All 3 peer selection techniques were used: random, end-to-end, and topology aware.  Peer failures were simulated as well. 2.Internet Experiments  Six candidate peers across North America and Europe.  Four peers are included in the active set and two peers are replaced during the simulation.

Received Rate Comparison between Different Peer Selection Techniques

Summary PROMISE is a P2P system designed to work on top of a service called CollectCast. Three peer selection techniques are available: random, end-to-end, topology- aware. Topology inference technique is used to determine the best set of peers. Both simulation and Internet experiments were conducted using PROMISE.