Transcript IP Performance Measurements using Surveyor

Surveyor IP Performance
Measurements
Matt Zekauskas
[email protected]
June, 1999
NLANR/I2 Joint Techs
IP Performance Metrics
• IETF IPPM effort
– Framework and Connectivity RFC
– One-way delay and packet loss drafts
– Others: round-trip delay, 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 highbandwidth flows harder
• Erratic variation in delay makes realtime apps harder
Uses
• Problem determination
• Engineering (trends, loads)
• Monitor QoS
• Feedback to advanced applications
(for example, Tele-Immersion)
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
Measurement Machines
• Dell 400 MHz Pentium Pro
• 128 MBytes RAM; 8 GBytes disk
• BSDI Unix
• TrueTime GPS card and antenna (coax)
• Network Interface (10/100bT, FDDI,
OC3 ATM in alpha)
• 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 ± 100 s  10 s soon
– Measurements centrally managed
• Concurrent routing measurements
Ongoing Tests - Routing
• Traceroute to same sites as One-Way
delay
• Scheduled with Poisson process
– average rate: one every 10 minutes
Central Database Machine
• Collects performance data from the
measurement machines [ssh, pull]
• Stores the data in a home-grown
database
• So far, all measurements taken on-line
• Serves data and summaries to reporting
and analysis tools [http]
Current Surveyor Deployment
• 50 machines
– Universities
– Tele-Immersion Labs
– National Labs
– …others
• 1883 paths
–
–
–
–
NASA Ames XP
I2 gigaPoPs (some)
CA*net2 gigaPoPs
APAN sites
– Abilene router nodes
up with NTP,
awaiting GPS
Reporting and analysis tools
• Web based tools
• Daily summary reports
• Integration with route measurements
• Java applet to dynamically graph
almost ready
• Developing asynchronous notification
of anomalies
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)
Lessons so far
• Routing is asymmetric
• Even when routing is symmetric,
queuing is asymmetric
• Can detect level 2 changes (SONET
failover or ATM)
• HPC connections do fall back to
commodity paths, sometimes
frequently or for long periods
Summary
• One-way Delay and Loss are
– practical
– useful
• Surveyor infrastructure growing
• Dynamic plotting, asynchronous
notification coming soon
• Now focus on analysis and applications
More info
• Surveyor project info
– http://www.advanced.org/surveyor/
• Access to plots
– http://ippm-db.advanced.org/plots/
• IETF IPPM WG
– http://www.advanced.org/IPPM/
• My email: [email protected]