Some people replied me about my questions. thanks for reply.
However, what I want to know ultimately is something like technical proof or standard or experimentation information
they can logically support SLA values in provider's IP network.
For example, regarding packet loss, I found information it is based on voip service tolerance (al least below 1% packet loss).
but some provider announce they can guarantee 0.3% packet loss. Where does 0.3% come from ?
Can anyone give me an answer about this question ? In fact I am going to make some guideline of network quality of my network.