This element has a conditional presence. The business rule that indicates presence is under study. Number of minutes ahead (+) or behind (-) GMT of the local time zone in which the service is consumed. minutes The E-Model Quality Rating Factor, per ITU-T Recommendation G.107, "The E-Model, A Computational Model for Use in Transmission Planning", R=100 (excellent) to 0 (bad). Alternative user perceived R factor derived from E-Model and IP network performance statistics. See ETSI TS-101-329-5 V1.1.1 (2000-11), Annex-E. R=100 (excellent) to 0 (bad).