IP SLA is a mechanism that checks the condition of a particular entity (jitter, echo request etc) and returns a value of whether or not it is OK. As such, the SLA statistics will focus on whether the SLA has been achieved or if it has failed. IP SLA is not designed to give more information about the state of jitter. Specifically, according to Cisco, the information provided is:
- Per-direction jitter (source to destination and destination to source)
- Per-direction packet loss
- Per-direction delay (one-way delay)
- Round-trip delay (average round-trip time)
Now if you want to determine more information about jitter on the network, even when its levels are acceptable, you need to use other monitoring tools such as Wireshark or Netflow. If you’re measuring jitter on an IP phone, Cisco phones have the option of viewing Average and Max jitter of an active call on the Call Statistics screen.
There are many additional options that you can configure when you set up an IP SLA for jitter. You can indeed set a threshold as well as many other settings. You can find out more about these at the following link:
MOS or Mean Opinion Score started out as a subjective measure of the quality of the sound of a voice in general and has been applied to telephony as well. People would rate the quality or the MOS of a particular service from 1 to 5 where 5 is face to face communication, or FM radio quality sound. Various characteristics affect the MOS such as the codec being used, as well as jitter of course.
Now because obtaining MOS ratings can be time consuming and can cost a lot since you actually need people to rate the quality of the voice service, an objective and automatic method of MOS measurement has been devised using algorithms which statistically mimic the human MOS ratings. These algorithms are standardized in the ITU-T PESQ P.862 standard. This is what is used in the Cisco device to estimate an MOS rating.
Any rating above 3.8 is considered good although this value may vary depending on who you ask. Anything below that can become noticeably degraded.
The following is a list of codecs and their MOS scores for reference.
I hope this has been helpful!