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Transcript
Internet Measurement and Analysis Vinay Ribeiro Shriram Sarvotham Rolf Riedi Richard Baraniuk Rice University Internet • Complex interaction of – Network protocols (routing, congestion control) – Applications (Web, email, streaming video/voice) • To improve performance – Need to understand Internet’s working – Need measurements and analysis tools Network Operations: Performance Issues •Avoid network congestion –Monitor traffic loads •Fault tolerance –Reroute traffic if link goes down • Must collect traffic statistics at routers/links • Key: measurement must not overload routers Measurement Granularity • Packet level: measure every packet • Connection level: measure aggregate information for each file transfer • Link level: measure only mean bit rate on link data volume and detail What are performance relevant statistics? Alpha/beta model for network traffic • Motivation: study burstiness in traffic • Connection-level analysis of available traces • Finding: typically one dominant connection during burst • Classify dominant connections as alpha, remaining as beta 5 x 10 x 10 5 x 10 3 2.5 2.5 2.5 2 = 1.5 1 0.5 0 0 2 + 1.5 1 0.5 2000 4000 6000 time (1 unit=500ms) Overall traffic 0 0 number of bytes 3 number of bytes 3 5 2 1.5 1 0.5 2000 4000 time (1 unit=500ms) 6000 Alpha traffic = all alpha connections 0 0 2000 4000 time (1 unit=500ms) Beta traffic = residual 6000 Implications of Alpha/Beta • Network control – Active Queue Management (AQM) should target alpha connections that cause bursts • Simulation: For realistic scenarios must simulate both alpha and beta components • Queuing analysis and network design Should consider both components – Gaussian beta component – spiky alpha component Network Users: Performance Issues • Users want to optimize performance – Use maximum bandwidth, minimize packet delay and loss • Internal routers uncooperative (security, technical issues) • Use probe packet delays measured by edge machines Available Bandwidth • Available bandwidth = unused bandwidth on path • Probing scheme must be non-intrusive (introduce light load on network) Chirp Probing • Chirp: exponential flight pattern of probes • Non-intrusive and Efficient: wide range of probing bit rates, few packets Estimation Algorithm Available bandwidth = probing rate at onset of queuing delay increase (congestion) Applications • Network path selection: download data over path with more bandwidth • Congestion control: find optimal rate to transmit data without congesting network Conclusions • Internet measurement and analysis tools required to improve performance • Measurement modules needed at routers as well as desktops URL: spin.rice.edu