Latency is the time for data to travel from source to destination. High latency makes applications feel slow even when bandwidth is plentiful.
Types of latency:
Propagation delay. Time for signals to travel through cables.
Transmission delay. Time to push bits onto the wire.
Processing delay. Time for routers to process packets.
Queuing delay. Time spent waiting in buffers.
Measurement methods:
- Ping for basic round-trip time
- Traceroute for per-hop latency
Targets:
- Voice: under ms one-way
- Interactive apps: under ms for responsive feel