This ATIS Technical Report (TR) provides guidance on the usage in North America of two parameters required to configure the Upstream Power Back-Off (UPBO) functionality defined in ITU-T Recommendation G.997.1 [4] and G.993.2 [1]. These two parameters@ a and b @ are defined in Section 7.2.1.3.2 of G.993.2 [1]@ while the configuration in the ??CO MIB of G.997.1 [4] is defined as the Upstream Power Back-Off Shaped (UPBOSHAPED) parameters in section 7.3.1.2.14 of G.997.1. Configuration of a and b is required to allow proper operation of the UPBO function for VDSL2. At the time of publication of this TR@ neither the G.993.2 nor G.997.1 ITU Recommendations provides any guidance for the configuration of these parameters in a North American context; therefore this TR provides guidance in the following areas: ? Explanation of the technical meaning of these two parameters. ? Examples of the use of UPBO parameters a and b in a North American environment. ? Guidance on the configuration of these two parameters in North American implementations of VDSL2. Although this TR provides information on the configuration of these parameters@ the guidance is of an explanatory nature. Specifically this Technical Report is not an ATIS Standard and values in examples and the guidance in this Technical Report are not requirements for either default values or the field configuration for parameters a and b . The examples in this TR do not necessarily result in optimum values for either of these parameters in specific field situations and obtaining such optimum configuration for UPBO operation of VDSL2 may require field implementation specific information that is outside the scope of this TR. Issue 2 of this TR adds a discussion the UPBO ??a' and ??b' parameters for the US-3 band as utilized by the 30a VDSL2 profile. Purpose This TR provides technical guidance to the Industry@ that is network operators@ and vendors of VDSL2 equipment and operations support software@ on the meaning and usage of the VDSL2 UPBO a and b parameters for North American field implementations of VDSL2. Its purpose is to provide information on the technical meaning and guidance on the configuration of these two parameters. Application This TR provides guidance to network operators and vendors on the proper usage of the G.993.2 UPBO parameters a and b .