PTP

1. Precision time protocol (PTP)
2. SyncE

Precision time protocol (PTP)

• IEEE 1588
• synchronize time: phase
  • can also sync frequency
  • ns accuracy
• types
  • ordinary:
    • server: distribute time to secondaries
    • client: sync to master
  • boundary: synchronizes itself, does not forward further
  • transparent: does not synchronize itself, forwards further
    • E2E
    • P2P
• hierarchy
  • grandmaster (GM): best available clock ≡ active master
  • master (primary): time from GPS
  • member (secondary): time from PTP
• profiles
  1. G.8275.1: each node is PTP-aware
     • L2 mcast
  2. G.8275.2: partial timing network support
     • L3 unicast
• assumes symmetric delay
• NX-OS supports only boundary mode

(config)# feature ptp
(config)# ptp source <IP>

(config-if)# ptp

SyncE

• ITU-T G.8262
• syntonizes frequencies
• transmits clock info in Ethernet PHY
• accurate frequency distribution: signal on fiber is used
• faster lock time for PTP secondary
• increased holdover time (correct time after source is lost)