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, , streaming video/voice) To improve performance –Need to understand Internet’s working –Need measurements and analysis tools

Network Operations: Performance Issues Must collect traffic statistics at routers/links Key: measurement must not overload routers Avoid network congestion –Monitor traffic loads Fault tolerance –Reroute traffic if link goes down

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

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