Revising link capacity adjustment scheme for ASIC applications

Link Capacity Adjustment Scheme (LCAS) is a protocol in synchronous digital hierarchy (SDH) that provides hitless bandwidth adjustment of virtual concatenated (VCAT) signal under the control of network management system (NMS). With LCAS, SDH network thus can dynamically assign resources to meet the requirements of its subscribers. However, LCAS is a two-way handshake signaling with status messages exchanged continuously, which is difficult to be implemented within a single chip. To achieve an easier ASIC implementation, we revise the LCAS protocol to have a shorter handshaking procedure by adding MST bits in the reserved K4 bits and removing the complex mappings between TU12s and theirs SQs. Simulation results show that the revised LCAS shortens the period of handshaking greatly and synthesis results show that the size of logic is reduced effectively. We believe the new scheme as a protocol will be accepted and applied in future.