The world’s telephone network providers have invested an enormous amount of money over the past 15 years to build a reliable backbone network based on SONET/SDH. The rapid increase in the volume of data traffic makes it critical for these carriers to provide efficient data transport. Due to the capital cost of deploying new networks and the training of the craftspeople and to run them, there has been a great desire to evolve the existing SONET/SDH network, rather than replace it or build overlay networks. This desire has led to the development of the standards for SONET/SDH virtual concatenation, its associated Link Capacity Adjustment Scheme (LCAS), and the Generic Framing Procedure (GFP) for mapping data efficiently into virtually concatenated channels. This paper explains LCAS’ role in the evolving SONET/SDH network, with respect to allowing dynamic bandwidth adjustment and efficient network restoration.