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IP Performance Measurements using
SurveyorMatt Zekauskas
Guy Almes, Sunil KalidindiAugust, 1998
ISMA 98
Outline
• Background• Surveyor infrastructure• Reporting and analysis• Status
I: Background
• Internet topology is increasingly complex
• Commonly used measurement tools (like ping and traceroute) are inadequate
• Result: users don’t understand the Internet’s performance and reliability
IP Performance Metrics
• IETF IPPM effort– Framework RFC– One-way delay and packet loss drafts– Others: connectivity, bulk transfer, DV
• Surveyor: implementation of one-way delay and packet loss metrics
Motivation for measuring delay • Minimum of delay:
transmission/propagation delay • Variation of delay: queuing delay• Large delay makes sustaining
high-bandwidth flows harder• Erratic variation in delay makes
real-time apps harder
Uses
• Problem determination• Engineering (trends, loads)• Feedback to advanced applications
(e.g., Tele-Immersion, CMU’s Odyssey)
• Monitor QoS
One-way versus round trip
• Paths are asymmetric • Even when paths are symmetric,
forward and reverse paths may have radically different performance - asymmetric queuing
II. The Surveyor Infrastructure• Measurement machines at campuses
and at other interesting places along paths (e.g., gigaPoPs, interconnects)
• GPS to synchronize clocks• Centralized database to store
measurement data• Web based reporting and analysis
tools
II. Surveyor Infrastructure
Measurement machines
Measurement Machines
• Dell 400 MHz Pentium Pro • 128 MBytes RAM; 2 GBytes disk• BSDI Unix• TrueTime GPS card and antenna• Network Interface (10/100bT,
FDDI)• Special driver for the GPS card
Measurement Technology• Active tests of one-way delay and loss
– Measurement daemon– Test packets time-stamped with GPS time– Back-to-back calibration: 95% of
measurements ± 50 s– Measurements centrally managed
• Truer-time daemon to watch clocks
Ongoing Tests
Ongoing Tests - Delay
• Type-P– 12 byte UDP packets, 40 bytes total– Port “random” per session
• Scheduled using a Poisson Process– average rate: 2 per second
• “Mostly” full mesh
Ongoing Tests - Routing
• Traceroute to same sites as One-Way delay
• Scheduled with Poisson process– average rate: one every 10 minutes
Collecting Results
Central Database Machine
• SGI Origin 200• 2 processors, 256MB• 327GB Fibrechannel-attached RAID
for data storage(DataDirect Networks EV-1000)
Central Database Machine
• Collects performance data from the measurement machines [ssh, pull]
• Stores the data in a home-grown database
• Serves data and summaries to reporting and analysis tools [http]
Current Surveyor Deployment• 28 machines, 623 paths
– CSG Schools– Tele-Immersion Labs– National Labs– NASA Ames– CA*net2 Ottawa site– Auckland, NZ– …others
Surveyor Map (N. America)
III. Reporting and analysis tools• Web based Tools• Daily summary reports• Integration with traceroute
measurements
Daily summary reports
• Take a 24-hour sample for a given path
• Divide it into one-minute sub-samples
• For each one-minute sub-sample:– Minimum delay (blue)– 50th percentile (green)– 90th percentile (red)
Example daily reports
• Advanced Network & Services and University of Chicago– path is symmetric– asymmetric queuing
Examples (continued)
• Advanced Network & Services and University of Pennsylvania– path asymmetric
Examples (continued)
• CMU to Brown University
Examples - Route Change
• Advanced Network & Services toPenn State University
• Route change switched providers, and removed one provider from the path
Examples - Auckland
• University of Auckland, NZ toUniversity of Washington, Seattle
• Asymmetric queuing, congested trans-pacific path
IV Status
• Deployment rate: 1/week• Planned: Abilene backbone
– probe at each backbone router– experiment with piecewise delay
Full Mesh of End-to-end Paths
O(N2) paths
Paths with Exchange Points
O(X2+N)
Abilene
Universities
gigaPoPs
Router Nodes
Near-term improvements
• Improve measurement software– time stamping in-kernel: to scale
without losing accuracy
• New and improved analyses– real-time display tools– flag interesting paths– trends …– improved data export to other sites
Summary
• One-way Delay and Loss are – practical – useful
• Surveyor infrastructure growing• Now focus on analysis and
applications
More info
• Surveyor project info– http://www.advanced.org/surveyor/– Email: [email protected]
• Access to plots– Email me - [email protected]
• IETF IPPM WG– http://www.advanced.org/IPPM/
