Unanswered Question
May 11th, 2009

) PTP service :

I understand that we can enable ptp on only one interface while working on MWR device Got the following error when i try to enable on one more interface.

2(config-if)#ptp enable

%Error: can not have more than 1 ptp port

In this scenario, if a device is connected to two devices how it propogates ptp information to the other.

2) Recovered-clocking:

We can configure master/slave in a single device, so in case of having master/slave configured in two devices which are in the same network, which will be acting as master and slave.

3) Commands to know which is master and slaves in a given network. What is the protocol will be used internally to identify this

4)please give a detailed explanation on PTP where its is used?Network clocks like adaptive,differential,network etc...why its used where its used?

5)whats the difference between PTP and NTP

I have this problem too.
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Paolo Bevilacqua Tue, 05/12/2009 - 08:10

Hi, considering you're a cisco employee, you should have ample resources to answer your questions.

It's always a bit chilly to see cisco engineers asking in what primarily is a customer's forum.

Leo Laohoo Tue, 05/12/2009 - 14:02

The Precision Time Protocol (PTP), as defined in the IEEE 1588 standard, synchronizes with nanosecond accuracy the real-time clocks of the devices in a network. The clocks in are organized into a master-member hierarchy. PTP identifies the switch port that is connected to a device with the most precise clock. This clock is referred to as the master clock. All the other devices on the network synchronize their clocks with the master and are referred to as members. Constantly exchanged timing messages ensure continued synchronization.

NTP synchronizes the timekeeping among a set of distributed time servers and clients. This synchronization allows the events to be correlated when the system logs are created and the other time-specific events occur.

An NTP server must be accessible by the client switch. NTP runs over User Datagram Protocol (UDP), which runs over IP. NTP is documented in RFC 1305. All NTP communication uses Coordinated Universal Time (UTC), which is the same as Greenwich Mean Time. An NTP network usually gets its time from an authoritative time source, such as a radio clock or an atomic clock that is attached to a time server. NTP distributes this time across the network. NTP is extremely efficient; no more than one packet per minute is necessary to synchronize two machines to within a millisecond of one another.

NTP uses a stratum to describe how many NTP hops away a machine is from an authoritative time source. A stratum 1 time server has a radio or atomic clock that is directly attached; a stratum 2 time server receives its time from a stratum 1 time server, and so on. A machine running NTP automatically chooses as its time source the machine with the lowest stratum number that it is configured to communicate with through NTP. This strategy effectively builds a self-organizing tree of NTP speakers.

Configuring PTP

Hope this helps.


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