Transcript Document

Fundamentals of Internet Measurement:
a Tutorial
Nevil Brownlee, Chris Lossley, “Fundamentals of Internet
Measurement: a Tutorial,” CMG journal of Computer Resource
Management, Issue 102, Spring 2001
정하경
2006.12.04
Presenter: Jung, Hakyung
Outline
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Motivation
Measurement topics
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H/W versus S/W approaches
Active versus Passive measurements
Examples
Main observations in the past research
Conclusion
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Motivation
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Network troubleshooting
Protocol debugging
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Workload characterization
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Test out “new, improved” version of network applications
and protocols
design of better protocols and network for supporting the
application
Performance evaluation and improvement
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Identifying performance bottleneck
•
New versions of the protocols can provide better performance
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Measurement Topics
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Hardware approaches
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Special-purpose tools designed to collect and analyze
network data
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•
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Often expensive
Better functionality and performance
Software approaches
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Modify the kernel for the packet-capture capability
•
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e.g. tcpdump
Access logs recorded by Web servers or proxies
4/15
Software approach example:
MIPv6 traffic measurement
CN
IPv6 Network
IPFIX
Flow Collector
IPv6 Router
IPFIX
flow data
HA
FA
FA
MIPv6 Access Router
with IPFIX
AP
MN
5/15
Measurement Topics
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Passive measurements
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Observe normal network traffic without creating additional
traffic
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e.g. counting # of packets traveling through routers
Do not perturb the network
Rely on traffic flowing across the link being measured
Active measurements
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Send test traffic needed to make the measurement
•
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e.g. ping, traceroute utilities
Generate extra traffic onto a network, thereby affecting
measurement results
6/15
Passive techniques:
workload analysis (1/3)
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A matrix of traffic from
source to destination
ASes
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2 minute sample from FIXwest in April 1998
can be used to optimize
topology or to determine
the traffic balance among
ISPs
since AS is the unit of
routing relationship
7/15
Passive techniques:
workload analysis (2/3)
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A matrix of traffic from
source to destination
countries
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2 minute sample from FIXwest in April 1998
gives a perspective on
international commerce
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Passive techniques:
workload analysis (3/3)
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Cumulative distribution of
packet sizes, and of bytes
by the size of packets
carrying them
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peaks at sizes of 44, 552,
576, and 1500 bytes
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Active technique:
Internet mapping project
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skitter, a tool for
dynamically discovering
and depicting global
Internet topology
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uses the same procedures
with traceroute utility
gathers connectivity
information, RTT, path data
10/15
Active technique:
RTTs measurement
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The distribution of RTTs
for 1600 probe packets
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nearly symmetric &
relatively large distribution
The plot of delay values
measured along the path
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congestion between
hop 11 and hop 12
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Observations in the past
research (1/3)
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Packet traffic is non-uniformly distributed
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10% of the hosts account for 90% of the traffic
Client-Server paradigm
Network traffic exhibits “locality” properties
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Packets are not independent; rather part of a higher-layer
logical flow of information
Temporal locality (time-based correlation)
Spatial locality (geography-based correlation)
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Observations in the past
research (2/3)
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The packet arrival process is not Poisson
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Poisson arrival process
• Events occur independently at random times
• Inter-arrival times between events are exponentially
distributed and independent
• Memoryless property
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Inter-arrival times between packets are not exponentially
distributed, nor are they independent
Packet arrival process is bursty
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The session arrival process is Poisson
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Users seen to operate independently at random
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Observations in the past
research (3/3)
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Traffic flows are bi-directional, but often
asymmetric
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Download-intensive nature of the Web
Internet traffic continues to change
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Traffic volume, traffic mix, protocols, applications, users
Data set collected from an operational network represents
bye one snapshot at one point in time in the evolution of the
Internet
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Conclusion
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Role of network traffic measurement
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Design, testing, evaluation of Internet protocols &
applications
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Internet traffic measurement Methodology
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Summary of the main observations from the past
network measurement research
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Internet traffic continues to change
15/15
Reference
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N. Brownlee, C. Lossley, “Fundamentals of Internet
Measurement: a Tutorial,” CMG journal of Computer Resource
Management, Issue 102, Spring 2001
KC Claffy, “Internet measurement and data analysis:
passive and active measurement,” NAE workshop, 1999
C. Williamson, “Internet Traffic Measurement, “ IEEE Internet
Computing, Vol. 5, No. 6, 2001
http://www.cybergeography.org/atlas/topology.html
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