while obviously being on same page as Tony Li I chime in with a bitsy bit here to keep perception straight
On Tue, Oct 7, 2025 at 6:30 AM Les Ginsberg (ginsberg) <[email protected]> wrote: > Tony – > ... > > > > If an LSP is received, checksum is validated, but the data in the LSP is > in some way different than what is in the LSP in the transmitters DB, then > we still have the actual TLV content which is in some way corrupted. In a > robust implementation the corrupt information would be detected and not > used. > > > in case that wasn't clear, LSP checksums are part of the HSNP hashes as well and they do contribute significantly to entropy (assuming they are reasonably uniformly distributed when LSP contents etc change even by small amount) Newest draft will go to double hashing which I'm still polishing (after experience with extensive flood reduction testing we see it generating better distributions of hashes which is not surprising given a serious amount of literature attesting to it). As small output here are bunch of hashes on close identifiers and very small changes in checksum (forcing low entropy) versus checksums are more realistic (i.e. distributed evenly across 2^16). log2 hamming distance distros clearly show And ultimately, in the last thread opened I gave a back of the envelope stochastic math of probabilities involved hope that all helps to clarify things a bit better 0101:0101:0000.00-04 Seq# 0001 Csum: $13E7 (low entropy csum $1EF1) Low Entropy checksum Hash 1EF51AF1 realistic csum hash: 13E317E7 0101:0101:0000.01-04 Seq# 0001 Csum: $FB08 (low entropy csum $1EF2) Low Entropy checksum Hash 1FF61AF3 realistic csum hash: FA0CFF09 0101:0101:0000.00-04 Seq# 0002 Csum: $88E0 (low entropy csum $1EF3) Low Entropy checksum Hash 1EF71AF3 realistic csum hash: 88E48CE0 0101:0101:0000.01-04 Seq# 0002 Csum: $BDFC (low entropy csum $1EF4) Low Entropy checksum Hash 1FF01AF5 realistic csum hash: BCF8B9FD 0101:0101:0000.00-07 Seq# 0001 Csum: $30E6 (low entropy csum $1EF5) Low Entropy checksum Hash 1EF219F5 realistic csum hash: 30E137E6 0101:0101:0000.01-07 Seq# 0001 Csum: $83AC (low entropy csum $1EF6) Low Entropy checksum Hash 1FF119F7 realistic csum hash: 82AB84AD 0101:0101:0000.00-07 Seq# 0002 Csum: $3FCB (low entropy csum $1EF7) Low Entropy checksum Hash 1EF019F7 realistic csum hash: 3FCC38CB 0101:0101:0000.01-07 Seq# 0002 Csum: $821A (low entropy csum $1EF8) Low Entropy checksum Hash 1FFF19F9 realistic csum hash: 831D851B 0401:0401:0000.00-04 Seq# 0001 Csum: $233A (low entropy csum $1EF9) Low Entropy checksum Hash 1BF81FFC realistic csum hash: 263B223F 0401:0401:0000.01-04 Seq# 0001 Csum: $6B7B (low entropy csum $1EFA) Low Entropy checksum Hash 1AFB1FFE realistic csum hash: 6F7A6A7F 0401:0401:0000.00-04 Seq# 0002 Csum: $1261 (low entropy csum $1EFB) Low Entropy checksum Hash 1BFA1FFE realistic csum hash: 17601364 0401:0401:0000.01-04 Seq# 0002 Csum: $BBA5 (low entropy csum $1EFC) Low Entropy checksum Hash 1AFD1FF8 realistic csum hash: BFA4BAA1 0401:0401:0000.00-07 Seq# 0001 Csum: $1E48 (low entropy csum $1EFD) Low Entropy checksum Hash 1BFF1CF8 realistic csum hash: 1B4A1C4D 0401:0401:0000.01-07 Seq# 0001 Csum: $D679 (low entropy csum $1EFE) Low Entropy checksum Hash 1AFC1CFA realistic csum hash: D27BD47D 0401:0401:0000.00-07 Seq# 0002 Csum: $F8D9 (low entropy csum $1EFF) Low Entropy checksum Hash 1BFD1CFA realistic csum hash: FDDBFADC 0401:0401:0000.01-07 Seq# 0002 Csum: $3864 (low entropy csum $1F00) Low Entropy checksum Hash 1B021D04 realistic csum hash: 3C663A60 0104:0104:0000.00-04 Seq# 0001 Csum: $501B (low entropy csum $1F01) Low Entropy checksum Hash 1A001E04 realistic csum hash: 551A511E 0104:0104:0000.01-04 Seq# 0001 Csum: $3ADF (low entropy csum $1F02) Low Entropy checksum Hash 1B031E06 realistic csum hash: 3EDE3BDB 0104:0104:0000.00-04 Seq# 0002 Csum: $A7D4 (low entropy csum $1F03) Low Entropy checksum Hash 1A021E06 realistic csum hash: A2D5A6D1 0104:0104:0000.01-04 Seq# 0002 Csum: $85AC (low entropy csum $1F04) Low Entropy checksum Hash 1B051E00 realistic csum hash: 81AD84A8 0104:0104:0000.00-07 Seq# 0001 Csum: $2631 (low entropy csum $1F05) Low Entropy checksum Hash 1A071D00 realistic csum hash: 23332434 0104:0104:0000.01-07 Seq# 0001 Csum: $BB78 (low entropy csum $1F06) Low Entropy checksum Hash 1B041D02 realistic csum hash: BF7AB97C 0104:0104:0000.00-07 Seq# 0002 Csum: $9C50 (low entropy csum $1F07) Low Entropy checksum Hash 1A051D02 realistic csum hash: 99529E55 0104:0104:0000.01-07 Seq# 0002 Csum: $60DE (low entropy csum $1F08) Low Entropy checksum Hash 1B0A1D0C realistic csum hash: 64DC62DA 0104:0101:0007.00-04 Seq# 0001 Csum: $D143 (low entropy csum $1F09) Low Entropy checksum Hash 1F0D190B realistic csum hash: D147D741 0104:0101:0007.01-04 Seq# 0001 Csum: $A9EE (low entropy csum $1F0A) Low Entropy checksum Hash 1E0E1909 realistic csum hash: A8EAAFED 0104:0101:0007.00-04 Seq# 0002 Csum: $BAA5 (low entropy csum $1F0B) Low Entropy checksum Hash 1F0F1909 realistic csum hash: BAA1BCA7 0104:0101:0007.01-04 Seq# 0002 Csum: $040C (low entropy csum $1F0C) Low Entropy checksum Hash 1E08190F realistic csum hash: 0508020F 0104:0101:0007.00-07 Seq# 0001 Csum: $BD59 (low entropy csum $1F0D) Low Entropy checksum Hash 1F0A1A0F realistic csum hash: BD5EB85B 0104:0101:0007.01-07 Seq# 0001 Csum: $4D65 (low entropy csum $1F0E) Low Entropy checksum Hash 1E091A0D realistic csum hash: 4C624866 0104:0101:0007.00-07 Seq# 0002 Csum: $24E7 (low entropy csum $1F0F) Low Entropy checksum Hash 1F081A0D realistic csum hash: 24E021E5 0104:0101:0007.01-07 Seq# 0002 Csum: $BF1F (low entropy csum $1F10) Low Entropy checksum Hash 1E171A13 realistic csum hash: BE18BA1C 6.94 ┤ ╭╮ ╭╮ ╭╮ ╭╮ 5.78 ┤ ╭╮ ││ ││ ╭╮ ╭╮ ││ ││ 4.62 ┤ ╭╮ ││ ││ ││ ││ │╰╮ │╰╮ │╰╮ 3.47 ┤ ││ │╰╮╭╯╰╮╭╯╰╮ │╰╮ │ │╭╯ │ │ │ ╭╮ 2.31 ┤ ╭╯╰╮╭╯ ││ ││ │╭╯ │╭╯ ││ │╭╯ │ │╰╮ ╭─╮ 1.16 ┤ │ ││ ││ ││ ││ ││ ╰╯ ╰╯ ╰─╯ ╰─╯ │ 0.00 ┼──╯ ╰╯ ╰╯ ╰╯ ╰╯ ╰╯ ╰───────────────────────────────────────────────────────────────────────────────────── Log2 Hamming Distribution of Hashes built over low entropy mean 10.266712614358338 6.66 ┤ ╭╮ ╭╮ ╭╮ ╭╮ 5.55 ┤ ╭╮ ││ ││ ││ ││ ╭╮ 4.44 ┤ ╭╮ ││ │╰╮ │╰╮ │╰╮ │╰╮ │╰╮ ╭╮ ╭╮ 3.33 ┤ ╭╮ ││ │╰╮╭╯ │╭╯ │╭╯ │ │ │ │ │ │╰╮ │╰╮ 2.22 ┤ ││ ╭╯╰╮╭╯ ││ ││ ││ │╭╯ │╭╯ │╭╯ │ │ │ ╭─╮ 1.11 ┤ ╭╯╰╮│ ││ ││ ╰╯ ╰╯ ╰╯ ╰╯ ╰╯ ╰─╯ ╰─╯ │ 0.00 ┼──────────╯ ╰╯ ╰╯ ╰╯ ╰───────────────────────────────────────────────────────────────────────── Log2 Hamming Distribution of Hashes built over realistic checksums mean 16.009700960724025
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