A Scalable Content-Addressable Network

1
A Scalable Content-Addressable Network

• Sylvia Ratnasamy, Paul Francis, Mark Handley,
  Richard Karp, Scott Shenker
• Proceedings of ACM SIGCOMM 01
• Sections 3.3 3.6
• ?a???s?as?
• ????ß??a ?as?????

2
?e?t??se?? S?ed?as??

• ??daµe st?? p??????µe?e? e??t?te?, ?t? ??µß?? p??
  e??a? ?e?t?????? st? CAN µp??e? ?a ap????? p????
  ?????µet?a ?a? p???? IP ??µata µeta?? t???
• Se µ?a a?a??t?s?
• µ?s? s??????? ?a??st???s? d??d?s?? (average total
  latency) µ?s?? a???µ?? CAN hops µ?s? ?a??st.
  d??d?s?? ???e hop
• ???spa???µe ?a µe??s??µe e?te t? µ???? t??
  µ???pat???, e?te t?? ?a??st???s? d??d?s?? ??a
  ???e hop
• ? a???s? t?? a???µ?? t?? d?ast?se?? µe???e? t?
  µ???? t?? µ???pat???
• ? ???s? p????? realities ep?s?? µe???e? t?
  µ???? t?? µ???pat???

3
?a??te?e? µet????? d??µ?????s??

• O? a?t? t? s?µe?? ???s?µ?p??????e ?? µ?t??
  e?t?µ?s?? ? ap?stas? t?? ?a?tes?a???
  s??teta?µ???? µeta?? t?? ??µß??-p???? ?a? t??
  ??µß??-p?????sµ?? (µ???? µ???pat???)
• ?p????µe ?a p??????s??µe se µ?a ße?t??s? p?? ?a
  a?t??at?pt???e? ?a??te?a t?? IP t?p?????a t??
  ??µß??
• ???e ??µß?? ?p??????e? t?? ????? RTT
  (Round-Trip-Time) se ep?ped? d??t??? ??a ?a???a
  ap? t??? ?e?t???? t??
• G?a s???e???µ??? p?????sµ?, ??a µ???µa p????e?ta?
  st? ?e?t??a µe t? µ???st? a?a????a p???d?? ??
  p??? t? RTT
• ???????ta? ta µ???p?t?a µe µ???? ?a??st???s?
  d??d?s??
• ?p?fe????ta? µe???a ß?µata

4
?a??te?e? µet????? d??µ?????s??

• ??t??eta µe t?? a???s? t?? a???µ?? t?? d?ast?se??
  ?a? t? ???s? p????? realities, ? d??µ?????s?
  p?? ßas??eta? se RTT, st??e?e? st? µe??s? t??
  ?a??st???s?? d??d?s?? µe?????ta? t?? ?a??st???s?
  ???e ß?µat?? ?at? µ???? t?? µ???pat??? ?a? ???
  st? µe??s? t?? µ????? µ???pat???
• ??t?? e?t?µ?s?? ap?te?esµat???t?ta? a?t?? t??
  routing te??????
• per-hop latency

overall path latency
path length
5
RTT-weighted routing

• ???s? t?p??????? Transit-Stub
• ??s? ?a??st???s? d??d?s?? t?? d??t??? µeta??
  t??a?a ep??e?µ???? ??µß?? p????-p?????sµ?? 115
  ms
• n µeta?? 28 ?a? 218
• ? d??µ?????s? µe ???s? RTT, µe???e? t?? per-hop
  latency ap? 24 ??? 40, a?????a µe t?? a???µ?
  t?? d?ast?se??
• ?? ???s?µ?p??????? pe??ss?te?e? d?ast?se??,
  ep?t?????eta? a??µa µe?a??te?? ße?t??s?

6
??p??????? e?a?s??t? ?atas?e?? t?? CAN d??t???

• ? µ??a??sµ?? ?atas?e??? t?? CAN a?a??te? ??µß???
  se ???e? t??a?a
• ?? ?e?t??e? e??? ??µß?? st? CAN de? ?????
  a?a??ast??? ???t???? IP-d?e????se??
• ?d????µaste se pe??e??a se????a d??µ?????s??
• p.?. ??a? ??µß?? st? Berkley ??e? t??? ?e?t????
  t?? st?? ????p?, ?ts? ??a µ???p?t? se ??µß? st?
  ???t??? Stanford µp??e? ?a pe???aµß??e? µa???????
  ??µß??? st?? ????p?
• ?? te?????? s?ed?as?? p?? pa???s??st??a? st??
  pa?ap??? e??t?te?
• p??spa???? ?a ße?t??s??? t?? ep????? t??
  µ???pat??? se ??a ?p????? d??t??
• de? ep??e????? ?a ße?t??s??? t? overlay d??t??
• ???a p??spa???µe ?a ?atas?e??s??µe CAN t?p?????e?
  p?? ?a ta???????? µe t?? IP t?p?????e?

7
??p??????? e?a?s??t? ?atas?e?? t?? CAN d??t???

• ?p???t??µe t?? ?pa??? e??? s?????? µ??a??µ?t??
  p.?. DNS servers p?? ?e?t??????? ??
  sta?µ??-???s?µa (landmarks) st? ??te??et
• ?e ß?s? t?? s?et???? ap?st?se?? t?? CAN ??µß??
  ap? a?t? t? s????? sta?µ??, ?????µe ??a e?d??
  ?ata?eµ?µ???? a???es?? se ??d???
• ???e ??µß??
• ??t?µ? t?? RTT ????? ??a ???e sta?µ? t?? s??????
• ?a????µe? t??? sta?µ??? µe a????sa se??? t??
  ?????? RTT
• ??a µe ß?s? t??? ?p?????sµ??? ?a??st???s??, ???e
  ??µß?? ??e? µ?a d??ta?? sta?µ??
• G?a m sta?µ??? ? m! d??at?? d?at??e??

8
??p??????? e?a?s??t? ?atas?e?? t?? CAN d??t???

• ??????a, ???????µe t?? ???? s??teta?µ???? se m!
  tµ?µata ?s?? µe?????? ?a? ?a???a a?t?st???e? se
  µ?a µ??? d??ta??
• ???p?? d?a????sµ?? se m! tµ?µata
• Te????µe µ?a sta?e?? ??????? d??ta?? t??
  d?ast?se?? (p.?. xyzxyzx)
• ???????µe t? ???? se m tµ?µata ?at? µ???? t?? 1??
  d??stas??
• ???e tµ?µa ?????eta? se m-1 tµ?µata st? 2?
  d??stas?
• ???e tµ?µa ?????eta? se m-2 tµ?µata st?? 3?
  d??stas? ?.?.?.
• ???????µ????, ? e?sa???? ???? ??µß?? ????ta? se
  t??a?? s?µe?? se ???????? t? ???? s??teta?µ????
• ???a, ???eta? se t??a?? s?µe?? se a?t? t? tµ?µa
  t?? ????? p?? s?et??eta? µe t? d??ta?? t??
  sta?µ?? t??

9
??p??????? e?a?s??t? ?atas?e?? t?? CAN d??t???

• ?? s?ept??? e??a? ?t? ???t???? t?p??????? ??µß??
  e??a? p??a?? ?a ????? t?? ?d?a d??ta?? sta?µ??
  ?a? s??ep?? ?a t?p??et????? st? ?d?? tµ?µa st?
  ???? s??teta?µ????. S??ep??, ?e?t??e? st? ????
  s??teta?µ???? p??a??? ?a ß??s???ta? t?p???????
  ???t? st? ??te??et
• ??t?? e?t?µ?s?? a?t?? t?? te?????? a???es?? se
  ??d???
• Latency stretch

Latency on the CAN network
Average latency on the IP network
10
??p??????? e?a?s??t? ?atas?e?? t?? CAN d??t???

• m 4 sta?µ??
• ??p??et?µ???? se t??a?a s?µe?a, µe µ???
  pe?????sµ? ?a ap????? t??????st?? 5 hops µeta??
  t???
• S?µa?t??? ße?t??s? µe ???s? a?t?? t?? te??????
• ?µ??, ? ?ata??µ? t?? ??µß?? st? ???? de? e??a?
  ?µ???µ??f? ??p??e? pe?????? p?????at????µ??e?
• ?? ?µ???µ??f? ?ata??µ? f??t??
• ? ???s? te?????? e??s????p?s?? f??t??, ?p?? ??a?
  ?pe?f??t?µ???? ??µß?? pa?ad?de? ??a µ???? t??
  ????? t?? se ??a? ????te?? f??t?µ???, e?a?e?fe?
  a?t? t? p??ß??µa