Lecture 3: Clocks
Terms you should know
Paul Krzyzanowski
February 17, 2021
Clock synchronization
- Clock synchronization
- Logical vs. physical clocks
- Clock drift
- Offset
- Jitter
- Drift compensation function (linear compensation)
- Time service
- Synchronization delay (latency)
- Cristian’s algorithm
- Clock accuracy in Cristian’s algorithm
- Berkeley algorithm
- Fault-tolerant average
- Network Time Protocol (NTP): goals
- NTP synchronization subnet
- Strata of clock servers
- Use of UDP
- Clock precision
- Clock accuracy
- Dispersion
- Simple Network Time Protocol (SNTP) vs. NTP
- Understand how to use the SNTP (NTP) forumula to find the offset
- Precision time protocol
- Best master clock
- Master-initiated sync
- PTP offset and delay
Logical clocks
- Lamport’s happened-before relation
- Logical clock timestamp
- Causal events
- Concurrent events
- Lamport timestamps
- Partial (causal) ordering
- Lamport global logical timestamps (total ordering)
- Deficiency of Lamport timestamps
- Purpose of vector clock
- Know how vector clocks get incremented
- Identifying causal and concurrent events with vector clocks
- Vector timestamps with process IDs