Measurements close to users
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1 Measurements close to users Anna-Kaisa Pietilainen, Renata Teixeira MUSE Team Inria Paris-Rocquencourt
2 Network performance disruptions are frustrating For users For ISPs 2
3 Home networks can cause performance disruptions Cross-traffic competes for bandwidth Large buffers and heavy uploads increase delays Poor WiFi increases jitter and reduce bandwidth Poor placement of access point Interference from other access points Contention from other devices Non-Wifi interference (e.g., microwaves, baby monitors) 3
4 Goal Assist users to diagnose performance problems in the home network Automatic detection: Is there a problem? Focus on performance disruptions that affect users Problem identification: where is the problem? More detailed diagnosis when problem is local 4
5 Outline User experience of network performance Measuring network performance close to users Correlating with user experience Home network performance: Home vs. Access Measurement vantage point: end-host vs. gateway Fathom: browser-based measurement platform 5
6 Approaches to measure performance close to users Active probing Based on issuing probes, analyzing response Passive analysis of user s traffic Tap incoming and outgoing traffic: tcpdump, pcap Monitor status of TCP connections 6
7 RTT from active probes: ping probe ICMP echo request d t0 m probe d RTT m reply ICMP echo reply t1 reply 7
8 RTT from passive measurements: tcptrace t0 m data 1 d RTT t1 ack 1 8
9 Other end-to-end performance metrics Metric Active Passive Loss ping/iperf TCP retransmissions Throughput iperf TCP/UDP data rates Delay variation/jitter iperf Difference between RTTs Available bandwidth Capacity pathload, spruce ShaperProbe iperf UDP More metrics IETF IP Performance Metrics Working Group More tools 9
10 Summary: passive vs. active Passive + No need to inject traffic + Measures performance experienced by users + Measures destinations that don t respond to probes Active + No need to tap user s traffic + Measure performance of paths even without traffic + Often used for diagnosis Privacy concerns Collection overhead Only measures paths with traffic Not direct measure of user experience Probing overhead Cover a large number of paths Continuous measurements 10
11 Outline User experience of network performance Measuring network performance close to users Correlating with user experience Home network performance: Home vs. Access Measurement vantage point: end-host vs. gateway Fathom: browser-based measurement platform 11
12 Challenges in measuring user perception User perception varies Per user, per environment, per application For a given user according to external factors Controlled environment versus field Can t ask frequent user feedback At most ~10 per day Orders of magnitude more network measurements (every millisecond) 12
13 Approaches to obtain user feedback Offline: out-of-bad feedback Interviews, diaries Pro: detailed feedback Con: infrequent feedback; hard to correlate with network metrics Online: Integrated in measurement tool System triggered, user triggered Pro: more frequent feedback; automation is easier Con: feedback can be harder to interpret 13
14 Online user feedback Which questions to ask? Easy to fill, not to annoy users Enough information to interpret results When to ask the questions? User triggered: depends on user System triggered: Experience sampling mechanism Cover diverse levels of network performance 14
15 Example: HostView A data collection tool for laptops (Mac OS / Linux) Mixed methodology Network traces Application process names Machine metrics User feedback Deployment (Nov 2010 Feb 2011) 40 users (14 countries) Most users ran tool for one month 15
16 HostView: User feedback System Trigged feedback Experience sampling methodology (ESM) Triggered based on state of machine 5 short questions about network performance At most 3 times a day User Triggered feedback I m annoyed button L Same questions as in ESM Can trigger as often as user wants 16
17 HostView: Example question 17
18 User vs. network reporting User perspective Good/poor performance according to the user Network and system perspective Good/poor performance according to network metrics Question: Do these co-occur? 18
19 1.1 1 Can t connect to some sites or services Time in minutes = 95th% RTT TCP RST TCP RETR 0 = 5th% 19
20 Everything is good! RTT Data Rate Time in minutes
21 Summary: correlating user feedback with network performance Hard to get feedback from users Many network performance samples without feedback Users are diverse in how they report a problem Raw network metrics alone are not enough Not all outliers affect the user perception 21
22 Outline User experience of network performance Measuring network performance close to users Correlating with user experience Home network performance: Home vs. Access Measurement vantage point: end-host vs. gateway Fathom: browser-based measurement platform 22
23 What is the speed of my access link? Home Network: AT&T DSL 6 Mbps Down, 512 Kbps Up access link ISP Network speedtest.net: 4.4 Mbps, 140 Kbps Netalyzr: 4.8 Mbps, 430 Kbps End host measurements are affected by confounding factors 23
24 Gateway better captures speed of Home Network: AT&T DSL access link 6 Mbps Down, 512 Kbps Up access link ISP Network speedtest.net: 4.4 Mbps, 140 Kbps Netalyzr: 4.8 Mbps, 430 Kbps Gateway: 5.6 Mbps, 460 Kbps Gateway can account for confounding factors 24
25 Gateway deployments access link Internet SamKnows/BISmark Nearby Server SamKnows Active measurements: throughput, delay, web performance, etc. FCC deployment: ~10,000 gateways BISmark OpenWRT router modified to perform active/passive measurements Georgia Tech deployment: ~100 gateways 25
26 Interpreting throughput results Different techniques measure different aspects of throughput 26
27 Summary: Gateway vs. end-devices Internet Home gateway Ideally placed between home devices and Internet But, have limited resources and deployment is harder Instrument end-devices Observe poor user experience But, have limited view of home network and development is harder 27
28 Outline User experience of network performance Measuring network performance close to users Correlating with user experience Home network performance: Home vs. Access Measurement vantage point: end-host vs. gateway Fathom: browser-based measurement platform 28
29 End-host measurements are challenging Measurement from end-hosts are vital Researchers to understand Internet Practitioners to diagnose user problems Hard to deploy measurements Developers: Portability, safety Users: need to install new software 29
30 A browser-based measurement Why browser? Flexibility, deployability Ubiquity of browser platform Fathom: Firefox extension Measurement API in JavaScript Web page performance System performance Active measurements 30
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CPSC 360 Fall 2017 Exam 1 Version 2 Solutions (last updated 10/19/2017) This exam is closed book, closed notes, closed laptops. You are allowed to have one 8.5x11 sheet of paper with whatever you like