prism: proxies for internet streaming media j. kurose, p. shenoy, d. towsley (umass/amherst) l. gao...
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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
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