docs: add SVS v4 specification - #23
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Uploads the SVS v4 wire-format specification (mhash, distinct FullStateVector / PartialStateVector / SvsDataRef TLVs, and the publish + pull recovery mode) alongside the existing v3 Specification.md. A 'Migration from Version 3' section (§9) summarizes the wire-format deltas. Source: https://github.com/named-data/ndnd/blob/psvs/docs/svs-v4.md Reference implementation: named-data/ndnd std/sync std/ndn/svs/v4
This was referenced Aug 11, 2026
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This PR adds the SVS v4 wire-format specification as
Specification-v4.md, alongside the existing v3Specification.md.Summary
SVS v4 extends the v3 wire format to support large sync groups by introducing:
mhash, TLV0xCB) carried in every Sync Data.VectorTypediscriminator with three distinct TLVs:FullStateVector(0xCD) — direct form carrying the complete State Vector.PartialStateVector(0xCE) — direct form carrying a publication-time subset, used when the encoded FULL exceedsSyncVectorThreshold.SvsDataRef(0x07) — publish-only form pointing to a retrievable full-vector Data.mhashmismatch or when the local FULL exceedsSyncVectorThreshold. Producers publish full-vector Data at/<group>/<node>/<boot>/32=sv/<version>and send a publish-only Sync Data referencing it./<sync-prefix>/v=4.SyncVectorThresholdis a fixed library constant of 1200 bytes.Reference implementation
The ndnd Go implementation in
named-data/ndnd(std/sync,std/ndn/svs/v4) ships against this spec on thepsvsbranch.File
Specification-v4.md(508 lines)This is a non-breaking, additive contribution —
Specification.md(v3) is left untouched. v3 and v4 deployments cannot interoperate on the same Sync Interest prefix (v=3vsv=4), per the §9 migration note.cc @yoursunny — addressing the request from named-data/ndnd#190.