PRISM: Proxies for Internet Streaming Media

J. Kurose, P. Shenoy, D. Towsley (UMass/Amherst)L. Gao (Smith College)G. Hjalmtysson, J. Rexford (AT&T Research - Labs)

Outline

goals of project services for streaming media research issues progress to date

Vision: enabling/enhancing a new service infrastructure

First generation servers single server, multiple clients end-end principle homogeneity in offered service

2nd generation service: proxy between server, clientsclient-tailored services enhanced scalability

Proxy Services: Motivation

Improved performance protect user from

poor throughput, delay, loss

exploit short RTT to client

exploit single provider of proxy-client path

Value-added services services not available at

server, tailored to client transcoding, error recovery,

interactive services

Exploit inside information knowledge of

QoS/provisioning on proxy-client path

knowledge of client bandwidth and buffer resources

Research Goals

Identification of proxy services System research issues

operating systems for proxies: resource allocation for QoS

middleware/interfaces for programmable services network protocols: error recovery, prefetch/prefix

caching, congestion control, service location/invocation

analysis, simulation, prototype and experiment

Sample Proxy Services

patching quality enhancement transcoding

Patching Service

problem asynchronous requests for long video streams low playback delay requirement

basic idea client receives ongoing transmission from

server retrieves initial portion from proxy

video flow

video flow

request

request

Multiple Clients Problem: multiple asynchronous requests for video basic ideas

batching, patching, segmented delivery, caching schedule, multicast video segments over different

multicast groups

video flow

video flow

Quality Enhancement

problem lossy, time-varying bw path from server to

proxy basic idea

proxy performs error recovery (ARQ, FEC) congestion control/buffering with server

simple clients see enhanced flow

enhancedvideo flow

video data

feedback

Operating System Support

flexible resource allocation mechanisms in proxy OS rate-based CPU, network, and disk schedulers

Challenge: design rate-based allocation mechanisms for large SMPs, disk arrays and multi-homed hosts

resource reservation mechanisms that provide performance guarantees to applications

Storage management techniques for proxy workloads Challenge: design techniques to handle workloads that

frequently read, write and delete diverse objects from disk cache

Platform: Use QLinux, a QoS-enhanced version of Linux that we have developed

Middleware/Interfaces: Pronto

programmable, active services

separation of control, forwarding

control: out of data path best effort asynchronous

implementation: stream thinning, active

congestion control reliable mcast traffic shaping

data pathforwarding engine

interface

Metacontrol

Network Protocols

Client/server/proxy batching, patching,

segmented delivery, catching protocols

data transfer: use of multiple multicast channels

control, signaling Congestion control

thinning, discard separate server-proxy,

proxy-client “connections”

Reliability enhancement: active repair services FEC time-critical error

control

Current Status

server/client implementation addition of proxy, services

QLinux: current version based on 2.2.x kernel rate-based CPU, packet, and disk schedulers

PRONTO partner with Z. Zhang (UMinn)

distribution of software

Summary

Proxy services enhanced performance valued added services proxy, clients “near” each other

System research issues operating systems resource allocation for QoS middleware for programmable services network protocols

Analysis, simulation, prototype and experiment