Dynamics of Prefix usage at an Edge router
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DYNAMICS OF PREFIX USAGE AT AN EDGE ROUTER Kaustubh Gadkari, Dan Massey and Christos Papadopoulos 1
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Dynamics of Prefix usage at an Edge router. Kaustubh Gadkari , Dan Massey and Christos Papadopoulos. Outline. Introduction – BGP RIB and FIB growth Motivation Methodology Results Conclusions and future w ork. Outline. Introduction – BGP RIB and FIB growth Motivation Methodology - PowerPoint PPT Presentation
Transcript of Dynamics of Prefix usage at an Edge router
DYNAMICS OF PREFIX USAGE AT AN EDGE ROUTERKaustubh Gadkari, Dan Massey and Christos Papadopoulos
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Outline Introduction – BGP RIB and FIB growth Motivation Methodology Results Conclusions and future work
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Outline Introduction – BGP RIB and FIB growth Motivation Methodology Results Conclusions and future work
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Inter-Domain Routing
CSU
129.82/16, 129.82/18 …
74.125/16, …
BGP
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BGP TablesRouter Memory
Routing Table(RIB)
Routing Updates Routing Updates
Forwarding Table(FIB)
Line Card Line Card Line Card
(Prefix, Path)
Forwarding Table(FIB)
Forwarding Table(FIB)
(Prefix, Outgoing Interface, Next
Hop)
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Outline Introduction – BGP RIB and FIB growth Motivation Methodology Results Conclusions and future work
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Table Growth The size of the
global routing is growing rapidly.
Increasing routing table size requires more memory on routers.
Operators are forced into faster upgrade cycles.
http://bgp.potaroo.net/as6447/
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Implications of Table Growth RIB size affects FIB size.
FIB scaling is arguably more important. FIBs stored on line card memory, which is
smaller and more expensive than main memory.
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Outline Introduction – BGP RIB and FIB growth Motivation Methodology Results Conclusions and future work
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Motivation Some current research focuses on scaling the
FIB by storing partial forwarding information.
But how to choose prefixes in a reduced FIBs? Prefixes receiving most packets should probably
be in the table. But are there better criteria to define a dominant
set? How does it behave?
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Motivation (contd.) Previous work focused on prefix popularity
over days or weeks. Tradeoff that prefers ease of selection.
Optimum prefix selection is a hard problem. Factors: traffic volume, activity patterns and
interplay of traffic dynamics
This work: understand prefix dynamics better.
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Outline Introduction – BGP RIB and FIB growth Motivation Methodology Results Conclusions and future work
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Methodology Monitor links to two tier-1 provider links
(1Gb/s each) at a regional ISP.
Dataset: two simultaneous 24-hour packet traces from these links.
Use outgoing packets only.
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Old Metric: Global Rank Rank prefixes
according to number of packets during the full 24-hour trace. This is the prefix’s
global rank.
Plot number of prefixes that account for a given fraction of packets.
Results corroborate previous studies.
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Measuring Prefix Dynamics Split traffic trace into small intervals (5
min).
Rank prefixes in each interval according to number of packets. We call this the prefix’s interval rank.
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New Metrics Duty cycle
Fraction of the total number of intervals in which the prefix receives at least one packet.
Mean rank difference Variation of a prefix’s interval rank from its
global rank.
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Outline Introduction – BGP RIB and FIB growth Motivation Methodology Results Conclusions and future work
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Duty Cycle Measure of prefix’s activity.High
duty cycle, high
traffic
Low duty
cycle, low
traffic
~200 prefixes
~56,000
prefixes
High duty
cycle, low
traffic
~24,000
prefixes
Low duty cycle, high
traffic
~10 prefixes
Global Prefix Rank
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Duty Cycle Observations Popular prefixes have high duty cycles.
Always get packets.
Several popular prefixes have a duty cycle of > 90%.
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Mean Rank Difference Measure of prefix’s “busy-ness”.
Stable Prefixes
Less than 1% of all prefixes,
40% of all packets
Generally Popular Prefixes5% of all prefixes, 55% of
all packets
Generally Unpopular Prefixes
60% of all
prefixes, 5% of all
traffic
Global Prefix Rank
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Outline Introduction – BGP RIB and FIB growth Motivation Methodology Results Conclusions and future work
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Conclusions Understanding dynamic behavior of FIB prefixes is
important for reduced-FIB designs. Proposed two new metrics: Duty cycle and mean
rank difference We corroborated previous work showing set of
dominant prefixes is small. New metrics characterize the dominant set better,
which is generally active and busy. Majority of the prefixes have very low activity opening
up caching opportunities. Results encouraging in terms of developing
reduced FIB designs.
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Future Work Investigate prefix dynamics at other
ISPs.
Investigate prefix dynamics at different intervals.
Develop a design for efficient forwarding using a reduced FIB.
