CoralCDN: A Network of Web Proxies for Peer-to-Peer Content Distribution
2004 · paper · Computer science
Presents CoralCDN, a peer-to-peer content distribution network where volunteer web caches let low-budget sites handle heavy demand. It relies on Coral, a latency-optimized indexing system built on a distributed sloppy hash table, to avoid hot spots.
Checked: PDF from usenix.org, fetched 5 Oct 2026. Page numbers are those of that PDF.
2 findings
Reference or label Section 4.4: "If probes indicate that 80% of a cluster's nodes are within acceptable TTLs and the cluster is larger" uses TTLs where RTTs are meant.
- p. 9 Section 4.4, fifth paragraph
within acceptable TTLs and the cluster is larger
Judge's note: Read on the p9 image. The same section defines acceptability as "the latency to 80% of the nodes be below the cluster's threshold", measured by "minimum round-trip-times (RTTs)", and the preceding sentence says "do not meet the RTT constraints". Elsewhere in the paper TTL means the time-to-live of stored references and DNS records, and hop count is never used as a clustering criterion. This is a wrong term with an evident fix.
Second check: another model agreed
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Wording "we ran 3 nodes on each of the earlier hosts for a total of 494 nodes" — the earlier hosts number 166 ("on 166 PlanetLab machines"), and 3 × 166 = 498.
- p. 12 Section 6.4, first paragraph
we ran 3 nodes on each of the earlier hosts for a total of 494 nodes
- p. 10 Section 6, experimental setup
First, on 166 PlanetLab machines
- p. 12 Section 6.4
we ran 3 nodes on each of the earlier hosts for a to-
- p. 10 Section 6
on 166 PlanetLab machines
Only the authors can say what is right here.
Judge's note: Read on pages 10 and 12. 3 × 166 = 498, not 494, and 494 is not a multiple of 3. A text search for 166 and 494 found no statement that hosts were dropped or ran fewer nodes. The downstream figures do not settle it: 494 × 400 × 60 is about 11.9 million (printed as approximately 12 million), and β·log n = 108 holds for either count. Only the authors can say whether some hosts were unavailable or the total is mistyped.
Second check: another model agreed
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14 minor (typos and the like; most checked by the judge only)
Wording Section 4.3 says "Recall that a set of nodes should form a cluster if their average, pair-wise RTTs are below some threshold", but the earlier definition (Section 2.3) is "a high-enough fraction [of] their pair-wise RTTs are below the level-i diameter threshold" and Section 4.4 requires "the latency to 80% of the nodes be below the cluster's threshold".
- p. 8 Section 4.3, first paragraph
age, pair-wise RTTs are below some threshold
- p. 4 Section 2.3, second paragraph
if a high-enough fraction their pair-wise RTTs are below
- p. 9 Section 4.4, first paragraph
the latency to 80% of the nodes be
- p. 4 Section 2.3, first paragraph
topologically close clients' networks
Only the authors can say what is right here.
Judge's note: All three passages were read on pp. 4, 8 and 9. An average below a threshold and a fraction below a threshold are different criteria, and the "Recall" sentence does not match what it recalls. "Average" may be loose wording, so this is a query for the authors. The missing "to" and "of" also raised in this cluster are judged under C004 and C005.
Second check: another model agreed
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Wording Section 4.4: "These prefix hints are of use to Coral's level function, which traceroutes clients in the other direction", but the interface in Section 2.3 has no level function: "levels(): Returns the number of levels in Coral's hierarchy and their corresponding RTT thresholds", and probing a target is assigned to nodes(level, count, [target], [services]).
- p. 9 Section 4.4, third paragraph
hints are of use to Coral’s level function, which tracer-
- p. 4 Section 2.3, interface list
levels(): Returns the number of levels in Coral’s hi-
- p. 9 Section 4.4, third paragraph
These prefix hints are of use to Coral's level function, which tracer-outes clients in the other direction
- p. 4 Section 2.3, interface list
levels(): Returns the number of levels in Coral's hi-erarchy and their corresponding RTT thresholds.
Only the authors can say what is right here.
Judge's note: On the p9 image "level" is set in italics like an interface function name. On p4 the interface lists put, get, nodes and levels; probing a target and using topology hints is described under nodes, and Section 3.1 (p5) says the same. The name in Section 4.4 does not match the declared interface. It could be an internal function that is never defined, or a slip for nodes, so only the authors can say.
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Typo Copy-edit slips: p3 "probes the client to determines its round-trip-time" (determine); p13 "CoralCDN's goal is to gives most users" (give); p15 ref [7] "U. Wisconson, Madison" (Wisconsin).
- p. 3 Section 2.2, step 3
the client to determines its round-trip-time
- p. 3 Section 2.2, step 3
probes the client to determines its round-trip-time
- p. 13 Section 7.2
goal is to gives most users
- p. 8 footnote 3
block-box
Judge's note: All three read on the page images for pp. 3, 13 and 15. The cluster's other two items ("prior replying", "block-box") are also on the page, but they are judged under C006 and C009.
Second check: none (judge only)
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Typo Unit misspelled in Section 2.3: "thresholds of ∞, 60 msec, and 20 msed for level-0, -1, and -2" (should be msec).
- p. 4 Section 2.3, second paragraph
60 msec, and 20 msed for level-0, -1, and -2
- p. 4 Section 2.3
20 msed for level-0, -1, and -2
- p. 4
thresholds of ∞, 60 msec, and 20 msed for level-0, -1, and -2
Judge's note: The p4 image shows "20 msed". The parallel sentence in Section 4.3 (p8) reads "60 msec, and 20 msec".
Second check: none (judge only)
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Typo Missing word in Section 2.2 step 11: "recording the fact that is now caching the URL" (should be "that it is now caching").
- p. 4 Section 2.2, step 11
recording the fact that is now caching the URL
Judge's note: Read on the p4 image; the subject "it" is absent in print.
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Typo Missing word in Section 2.3: "uses DSHTs to find Coral nameservers topologically close clients' networks" (should be "close to clients' networks").
- p. 4 Section 2.3, first paragraph
uses DSHTs to find Coral nameservers topologically close
Judge's note: The p4 image shows the line ending "topologically close" and the next line starting "clients' networks"; no "to" is printed.
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Typo Missing word in Section 2.3: "if a high-enough fraction their pair-wise RTTs are below the level-i diameter threshold" (should be "fraction of their").
- p. 4 Section 2.3, second paragraph
if a high-enough fraction their pair-wise RTTs are below
- p. 8 Section 4.3, first paragraph
Re-call that a set of nodes should form a cluster if their aver-age, pair-wise RTTs are below some threshold
- p. 4 Section 2.3, second paragraph
if a high-enough fraction their pair-wise RTTs are below the level-i diameter threshold
- p. 9 Section 4.4, first paragraph
acceptability requires that the latency to 80% of the nodes be below the cluster's threshold
Judge's note: Read on the p4 image; "of" is absent. The average-versus-fraction point that is also raised in this cluster is judged under C010.
Second check: none (judge only)
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Typo Missing word in Section 3.1: "status (via a UDP RPC) prior replying to a DNS query" (should be "prior to replying").
- p. 5 Section 3.1, last paragraph
prior replying to a DNS query
Judge's note: Read on the p5 image, right column.
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Typo Stray word in Section 4.2 item 1: "A node is or full with respect to some key k when" (should be "A node is full").
- p. 7 Section 4.2, Insertion Algorithm, item 1
A node is or full with respect to some key k
- p. 7
A node is or full with respect to some key k when
Judge's note: Read on the p7 image. The parallel item 2 reads "A node is loaded with respect to k".
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Typo Footnote 3: "using the Chord [31] routing layer as a block-box; difficulties in maintaining distinct clusters" (should be "black-box").
- p. 8 Footnote 3
block-box; dif
- p. 8 Footnote 3
as a block-box
- p. 8
as a block-box; difficulties in maintaining distinct clusters
Judge's note: Read on the p8 image, footnote 3.
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Typo Two wording slips: p.11 "Under heavy packet loss, the multi-system requires a few more timeouts" (elsewhere "multi-level system"); p.8 footnote 3 "routing layer as a block-box" (black-box).
- p. 11 Section 6.2, last paragraph
the multi-system requires a few
- p. 11 Section 6.2, last paragraph
the multi-system requires a few more timeouts as it traverses its hierarchy levels
- p. 8 footnote 3
as a block-box
Judge's note: Both are visible on the crops. The preceding sentences on page 11 say "multi-level systems" and "multi-level system", so "multi-system" has dropped the word "level". Footnote 3 on page 8 prints "block-box". Both are cosmetic.
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Typo Section 6: "The basic structure of the experiments were is follows." (garbled; should be "was as follows" or "is as follows").
- p. 10 Section 6, second paragraph
The basic structure of the experiments were is follows.
Judge's note: Read on the p10 image, left column.
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Typo "CoralCDN’s goal is to gives most users better performance to participating web sites" — "to gives" should be "to give".
- p. 13 Section 7.2, last paragraph
CoralCDN’s goal is to
- p. 13 Section 7.2, last paragraph
CoralCDN's goal is to gives most users better performance
Judge's note: Seen on the page 13 crop, across a line break ("goal is to / gives most users"). Grammar slip.
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Typo Reference [7]: "Technical Report 1361, CS Dept, U. Wisconson, Madison, Feb 1998" — "Wisconson" should be "Wisconsin".
- p. 15 Reference [7]
U. Wisconson, Madison
- p. 15 References, entry [7]
CS Dept, U. Wisconson, Madison
Judge's note: Seen on the reference-list crop of page 15. The entry prints "U. Wisconson, Madison", a plain misspelling of the place name.
Second check: none (judge only)