and out of a VCG without interrupting the existing service. LCAS does not provide the setting up and releasing of connections between intermediate nodes because this is the responsibility of Network Management Systems (NMS). Under a network failure scenario, the failed VCAT members are removed from the VCG by LCAS such that a client experiences a reduction in bandwidth rather than a total loss of connectivity. Replacement members can be provisioned through the NMS, and LCAS will hitlessly reintroduce them to the VCG to restore the connection to its original capacity. LCAS Protocol LCAS operation requires the VCG transmitter (source) and VCG receiver (sink) to maintain states on each member of the group and to exchange control messages to manage addition and removal of member links within the group. Bandwidth adjustments are initiated by the NMS by forwarding a request to the LCAS controller in the source and destination nodes. The controller then synchronizes the adjustment request using appropriate control packets and monitoring responses from the destination/sink node. Control packets are short- duration frames that are continuously transmitted between nodes. The control packets are used to synchronize the nodes and provide the status of each member and the VCG; they are transported in the H4 and K4 bytes of the path overhead for high-order VCAT and low- order VCAT, respectively (see Figure 11.13). These are reserved bytes that are not used for MFI and SQ in VCAT, as described earlier in the Concatenation section. Even if there is no change in the information that the VCAT contains, control packets are sent continuously, and each control packet describes the state of the member during the next control packet SO that all the planned changes of the VCG are hitless. The state of the member at the source side determines the reconstruction process at the sink, and the control (CTRL) field is used for this purpose. Each member in the LCAS process can be in one of five states. Four bits are defined and the values assi