gned, as recommended in ITU-T G.7042; they are shown in Figure 11.14. The default mode of VCAT without LCAS Multiframe 1 Multiframe 2 HO LCAS 512 ms 16 ms LO LCAS Bit 2 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 3031 32 Multiframe Fig. 11.13 Low-order and high-order LCAS overhead. Link Capacity Adjustment Scheme Multiframe 1 Multiframe 2 HO LCAS 512 ms 16 ms LO LCAS Bit 2 10 11 1213 14151617 18 19 20: Multiframe Fig. 11.14 LCAS control bits. is indicated by all zeros (because the reserved bits of VCAT are all set to zero). Four bits allow for possible future expansions of LCAS with more states. To check that members are cross-connected to the correct VCG, the Group Identification (GID) bit was introduced. The GID bit of all members of the same VCG has the same value in frames with the same MFI value. In this way, the sink can verify that all arriving members originate from a single VCG source. In SDH, it is common to validate a signal by the correct reception of three to five consecutive identical values. Because such a process would cause a significant delay in LCAS, a Cyclic Redundancy Check (CRC) is performed on every control packet after it has been received, and the contents are rejected if the check fails. The Member Status (MST) field reports the status of all members in a VCG from the sink to the source. At the sink, members belonging to a VCG are either functioning correctly (OK) or not (FAIL); members in the IDLE state are considered to be in the FAIL state. The MST field in each control packet has been limited to eight bits, and the MST of all members is distrib- uted across multiple control packets. In this way, the status of all possible members of a VCG will be refreshed every 64 ms for high-order LCAS and every 128 ms for low-order LCAS. (Recall that each control packet is 2 ms for high-order LCAS, with a maximum of 256 members per VCG; and 16 ms for low-order LCAS, with a maximum of 64 members per VCG. When the size of a VCG is resized by adding or removing members