Old Dog Consulting Old Dog Consulting Nanjing University Huawei Technologies GMPLS supports the description of optical switching by identifying entries in fixed lists of switchable wavelengths (called grids) through the encoding of lambda labels. Work within the ITU-T Study Group 15 has defined a finer-granularity grid, and the facility to flexibly select different widths of spectrum from the grid. This document defines a new GMPLS lambda label format to support this flexi-grid. This document updates RFCs 3471 and 6205 by introducing a new label format.