Time sync (NTP & PTP) Flashcards
Why is it important to synchronise time across a network
To correlate security events
Checking certificate validation
Changing encryption keys
managing password change intervals
What are the 2 most common time sync protocols used
Network time protocol (NTP)
Precision time protocol (PTP)
How does NTP work
it used a client server relationship to manage the synchronisation of time. the NTP client will query the NTP server and set its time based on the response.
What port does NTP use
UDP port 123
What is stratum
It is a concept to verify the accuracy of time. the NTP servers directly attached to the authoritative time source will be stratum 1.
A NTP client that queries the Stratum 1 server will be Stratum 2.
What is NTP peers
When 2 routers are configured to query an external authoritative time source to get the time.
Then the 2 routers will synchronise with each other to configure the time.
Multiple NTP servers can be configured for redundancy adding the optional key word “prefer” indicates which source to take the time from. NTP will use by default the server with the lowest stratum. The NTP router will only use ONE server to synchronise its time.
True or false
True
What is PTP mainly used for
Is used for precise time synchronisation for control systems, it offers very accurate time to nanoseconds, typical use will be energy providers when there is an on/off peak billing rates so time is very important.
How does PTP keep such an accurate time sync
PTP dynamically adjusts the time based on the delay from latency. PTPv2 messages will be sent with timestamps and they will be compared to adjust the time to be synchronised.
PTPv2 is backwards compatible with PTPv1
True or False
False - it is not backwards compatible
What are the modes that PTP can be configured in
Forward mode - sends the PTP packets in multicast traffic
Boundary mode - per port basis the switch will run and participates in the best master clock algorithm.
