PTP capabilities

For each PTP message type to be exchanged between the router and an external 1588 clock, a unicast session must be established using the unicast negotiation procedures. The router allows the configuration of the message rate to be requested from external 1588 clocks. The router also supports a range of message rates that it grants to requests received from the external 1588 clocks. The IEEE 1588 standard allows the grantor port to respond with a shorter duration than what was in the request. The router can accept such a grant and uses that duration. The router issues a renegotiation before the duration expires.

Table: Message rates ranges and defaults describes the ranges for both the rates that the router can request and grant.

Table: Message rates ranges and defaults
Message type Rates requested by the 7450 ESS, 7750 SR, 7950 XRS, and VSR Rates granted by the 7450 ESS, 7750 SR, 7950 XRS, and VSR

Min Max Min Max

Announce

1 packet every 16 seconds

8 packets/second

packet every 16 seconds

8 packets/second

Sync

1 packet/second

64 packet/second

1 packet/second

128 packet/second

Delay_Resp

1 packet/second

64 packets/second

1 packet/second

128 packets/second

(Duration)

300

300

1

1000

State and statistics data for each PTP peer are available to assist in the detection of failures or unusual situations.