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
