has the internet delay gotten better or worse?
DESCRIPTION
Has the Internet Delay Gotten Better or Worse?. Universidad Carlos III de Madrid 2010.6.30. DK Lee, Keon Jang, Changhyun Lee, Gianluca Iannaccone, Kenjiro Cho Sue Moon Associate Professor Department of Computer Science. Questions we need to answer first. Define Internet delay - PowerPoint PPT PresentationTRANSCRIPT
Has the Internet Delay Gotten Better or Worse?Universidad Carlos III de Madrid
2010.6.30.
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DK Lee, Keon Jang, Changhyun Lee, Gianluca Iannaccone, Kenjiro ChoSue Moon
Associate ProfessorDepartment of Computer Science
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Questions we need to answer first
1. Define Internet delay
2. Random sampling of Internet hosts
3. Estimate accuracy
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#1 Definition of Internet delay
• Delay distribution of host pairs in the Internet
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#2 Random sampling
• Issues in random sampling of IP addresses– Not all ASes have the same-size blocks of IP ad-
dresses– Not all blocks of IP addresses are in use– Not all IP addresses are in use– Not all IP addreses are always in use
=> /24 block as a unit of random sampling
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#3 Accuracy of estimates
• iPlane has shown better performance than landmark-based estimates
• All known delay estimation methodologies re-quire some form of active in-situ measure-ment but "path stitching"
Path:
Delay: rA + rAB + rB + rBC + rC
Overview of Path StitchingRouter-level paths and RTT from a to c ?
a c
A CStep 1. IP-to-AS mapping
A CStep 2. AS-level path inference from A to c
B
Step 3. Stitching path segments
:A: A::B B::C:B: :C:
rA rAB rB
rBCrC
What If There Are
7March 15, 2010, [email protected]
A::B ? B::C
:A: :C::B: ?
... ...
• Too few segments:
• Too many segments:
When path stitching produces no stitched path
• Case #1: No path segments in source or destina-tion AS
• Case #2: No segments in the middle of inferred AS path– inter-domain: use reverse segment– intra-domain: no solution
• Case #3: Segments does not rendezvous at the same address– Use approximation
When path stitching produces multiple stitched paths
• Use preferences rules#1 Same destination-bound prefix#2 Closeness to source and destination#3 Most recent vs median
Comparison with iPlane
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Very promising results:With accurate AS paths inference,
errors <= 20ms for 80% of pl-hard pairs
Now we ask the question again:Has it gotten better or worse?
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Review of random /24 prefixes
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BGP RIB Entries
http://bgp.potaroo.net/
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# of /24 blocks in the BGP tables
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Graphical distribution of host pairs (AS: Asia, AF: Africa, EU: Eu-rope, OC: Oceania, NA: North America, SA: South America)
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Varying sample sizes
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Response rates (n = 10,000)
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Our data set
• CAIDA's Skitter/Ark from 2004• RouteView and RIPE BGP tables
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Chronicle of Ark monitors
Delay distribution between random pairs of hosts
in 2004 and 2009
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2004 vs. 2009
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Delay distribution has gotten worse from 2004 to 2009 (Median delay 164.0 msec 211.6 msec)IP/AS hop counts decreased end-to-end
Regional Growth of the Internet
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Fraction of host pairs in NA decreased significantly from 40 % to 20%Fractions of all other regional pairs increased
NA: North AmericaSA: South AmericaAS: AsiaEU: EuropeOC: OceaniaAF: Africa
Delay Distributions for NA-NA and AF-EU pairs
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Delays distributions for NA pairs in 2004 and 2009 are almost identicalDelay performance for AF-EU pairs for most part improved
10% of AF-EU pairs experience delays more than 1 sec in 2009
For the same pairs of hostsin 2004 and 2009
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2004 vs. 2009
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Delay distributions for the same set of sample host pairs remain almost identical of slightly improved
IP/AS hop counts decreased
Concluding Remarks• We present the methodology for the Internet delay history recon-
struction and analysis: – Path stitching with existing measurements– Random sampling of the Internet host pairs
• We demonstrate the our approach is feasible in showing insight about the overall Internet delay distribution.
• Future work will focus on: – Rigorous statistical analysis about the sources of errors – Trends from 1999 to 2009
• Match the trend with the Internet-wide upgrades• Find the corroborating evidences for the observations
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BACKUP SLIDES
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Internet-wide Coverage:Approximations
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pl-easy pairs pl-hard pairs
we show incremental improvement in the fraction of pairs with stitched paths from 5% to 70% (for pl-hard pairs)
Preference Rules – (1)
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Pair #N
0
Dela
y (m
s)
Dela
y (m
s)De
lay
(ms)
pl-easy pairs
pl-hard pairs
estimated delay (min)without preference rules
real delay (max)real delay (min)
estimated delay (max)without preference rules
proximity+dst.bound (min)
proximity+dst.bound (max)All three rules
Preference rules bring the estimated delays close to the real measurements
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Delay distributions, from 2005 to 2009 in compari-son with 2004 (Different pairs)
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Median Delays from 2004 to 2009
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Delay distributions, from 2005 to 2009 in com-parison with 2004 (Same pairs)
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End-to-end delay performance for specific pairs