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NTP/1588 Protocol Review (Gap Analysis)

NTP/1588 Protocol Review (Gap Analysis). IETF 71 Philadelphia Greg Dowd March, 2008. NTP (Pros). Clock ensembling Strong/multi model authentication (server) Strong redundancy/clustering algorithms Multiple operating modes Extensive system level testing. NTP (Cons).

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NTP/1588 Protocol Review (Gap Analysis)

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  1. NTP/1588 Protocol Review(Gap Analysis) IETF 71 Philadelphia Greg Dowd March, 2008 Tictoc Protocol Review

  2. NTP (Pros) • Clock ensembling • Strong/multi model authentication (server) • Strong redundancy/clustering algorithms • Multiple operating modes • Extensive system level testing Tictoc Protocol Review

  3. NTP (Cons) • Timestamp specification ambiguity • Polling Rate Limitations • Stateless server requirement • Rigid specification of clock pll (sntp?) • Layer 3 implementation model • Lack of on path support (intermediate stratum servers/boundary clocks) Tictoc Protocol Review

  4. NTP (Cons) • Few technical developers • Ambiguous hardware timing support • No performance metrics for time or frequency • Path asymmetry issues • One way authentication mechanism • Monolithic conformance model (no “profile” ala 1588 except SNTP) Tictoc Protocol Review

  5. NTP (Suggestions) • Define client-only clock mode • Extend NTP to support follow up msgs • Extend NTP to support “profiles” • Extend domain concept to allow interoperation of multiple ntp pools • Propose definition of TC for NTP • Formalize acceptance of state in server Tictoc Protocol Review

  6. PTP (Pros) • Hardware timestamping support widely available • High sync rates • Alternative timescale support • Application specific profiles allowed • Multiple models available (Multicast/ unicast/hybrids) Tictoc Protocol Review

  7. PTP (Cons) • GM Clock failure mitigation (phase hit) • Single tier Authentication • Mgmt of protocol state machine only • No SNMP MIB for PTPv2 • No performance metrics for time Tictoc Protocol Review

  8. PTP (Cons) • Follow up routing issues • Path asymmetry issues • Physical layer mapping issues on time transfer • Path rate change issue for time transfer • Decoupling of 2 halves of time transfer equation Tictoc Protocol Review

  9. PTP (Suggestions) • Create clustering/failover mechanism in unicast model • Review TDD/FDD vs profiles • Define slave “clock” mgmt messages • Clarify TC frame updates vs layer 2/3 • Review authentication impact on timing/hardware Tictoc Protocol Review

  10. Common Suggestions • Investigate time-transfer/symmetry metrics for routing protocols • Create metrics for performance analysis (via ITU/pmol/ippm) • Define IWFs for syncE • Define time dispersion extensions for BCs Tictoc Protocol Review

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