Supplement 1 to Recommendation ITU-T D.50 provides considerations and options for traffic measurement in support of the provisions of Recommendation ITU-T D.50. It identifies different approaches for measuring IP traffic flow at the interconnect (at the Border Gateway Protocol interconnect or other interconnect point) between networks operated by administrations and operating agencies authorized by Member States. IP traffic flows can be measured at different points, including at the Border Gateway Protocol (BGP) interconnect point (for example by hardware or software within or external to BGP routers or related equipment). This Supplement is not intended to imply the need for any changes in the IETF Border Gateway Protocol (BGP). Options for traffic measurement that are not addressed in this Supplement are for further study.