In the RTCP XR VoIP Metrics block the R factor is an integer from 0 to 100, where 94 corresponds to toll quality, 50 or less is regarded as unusable, and 127 means unavailable.

Checked 2026-09-24

It is expressed as an integer in the range 0 to 100, with a value of 94 corresponding to 'toll quality' and values of 50 or less regarded as unusable.
Vendor
IETF
Product
RTCP XR
Subsystem
VoIP Metrics Report Block
Deployment
any
Region
not restricted
Release range
RFC 3611
Checked
2026-09-24

Sources

Cite this note

APA

WarmTransfer. (2026, September 24). Call quality metrics and MOS estimation: source note call-quality-metrics-rtcpxr-r-factor. WarmTransfer. https://warmtransfer.net/knowledge/claims/call-quality-metrics-rtcpxr-r-factor

BibTeX

@misc{warmtransfer-claim-call-quality-metrics-rtcpxr-r-factor,
  title  = {Call quality metrics and MOS estimation: source note call-quality-metrics-rtcpxr-r-factor},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/claims/call-quality-metrics-rtcpxr-r-factor},
  note   = {Source note call-quality-metrics-rtcpxr-r-factor, checked 2026-09-24}
}

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