has the internet delay gotten better or worse?

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, dklee@an.kaist.ac.kr

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