ased on B2 bytes, exceeds 10-3). It is indicated by setting bits 6-8 of transmitted K2 byte to "110." FERF is detected by MSTE when bits 6-8 of received K2 byte are set to "110" for three consecutive frames. Its removal is detected by MSTE when three consecutive frames are received with a pattern other than "110" in bits 6-8 of K2. Transmission of MS-AIS overrides MS-FERF. AU path AIS: AU Path AIS is sent by MSTE to alert downstream high order path terminating equipment (HO PTE) of detected LOP state or received AU Path AIS. It is indicated by transmitting "all 1s" pattern in the H1, H2, and H3 pointer bytes plus all bytes of associated VC-3 and VC-4. AU Path AIS is detected by HO PTE when "all 1s" pattern is received in bytes H1 and H2 for three consecutive frames. Its removal is detected when three consecu- tive valid AU pointers are received. Appendix A: SDH/SONET Signaling High order path remote alarm indication (HO Path RAI, also known as HO Path FERF): HO Path RAI is generated by HO PTE in response to received AU path AIS. It is sent upstream to peer HO PTE. It is indicated by setting bit 5 of POH G1 byte to "1." HO Path RAI is detected by peer HO PTE when bit 5 of received G1 byte is set to "1" for 10 consecutive frames. Its removal is detected when peer HO PTE receives 10 consecutive frames with bit 5 of G1 byte set to "0." TU path AIS: TU Path AIS is sent downstream to alert low order path terminating equipment (LO PTE) of detected TU LOP state or received TU path AIS. It is indi- cated by transmitting "all 1s" pattern in entire TU-1, TU-2, and TU-3 (i.e., pointer bytes V1-V3, V4 byte, plus all bytes of associated VC-1, VC-2, and VC-3 loaded by "all 1s" pattern). TU Path AIS is detected by LO PTE when "all 1s" pattern is received in bytes V1 and V2 for three consecutive multiframes. Its removal is detected when three consecutive valid TU pointers are received. Low order path remote alarm indication (LO path RAI, also known as LO Path FERF): LO Path RAI is generated by low order path terminating equipment