IBM T1.X1 is the ANSI accredited T1 Technical Subcommitee responsible for developing SONET standards, including SONET rates, formats and payload mappings. Its output is also brought into the ITU, for example as in ITU-T Recommendation G.707 [G.707]. The IETF-recommended way to run HDLC over SONET is to use the definition found in T1.X1 ANSI documents [T1.105.02, T1.105] and ITU document [G.707].