A network administrator notices that users are reporting poor audio quality during VoIP calls. The administrator suspects that jitter might be causing this issue. What should be done first to confirm if jitter is indeed the problem?
Use a protocol analyzer to measure the jitter values in the network traffic.
Monitor interface counters on network devices for errors and collision rates.
Replace all ethernet cables connected to VoIP devices with new ones.
Check the configuration and policies of Quality of Service (QoS) on the routers.