Alcatel-Lucent 1665 DMX complies with SONET 1+1 unidirectional and bidirectional revertive and nonrevertive protection switching requirements as specified in GR-253-CORE. Automatic line switches are initiated by signal fail and signal degrade conditions on the received low-speed (OC-3/12/48) or high-speed (OC-12/48/192) optical signal and are completed within 50 milliseconds of a signal failure. The signal's BER is calculated from violations of the SONET line overhead B2 parity bytes. Signal fail is declared for incoming LOS, LOF, line AIS, or BER exceeding a provisionable 10−3 to 10−5 threshold, while a BER exceeding a provisionable 10−5 to 10−9 threshold causes the signal degrade condition. Manual switch commands are available through the local and remote operations interfaces.
Important!
Alcatel-Lucent 1665 DMX supports Bidirectional Optimized 1+1 Linear Protection Switching per ITU-T G.841 Annex B. Bidirectional optimized 1+1 is designed to enable interoperability between Alcatel-Lucent 1665 DMX and SDH equipment. It is a separate switching scheme from standard 1+1 bidirectional and does not work with standard 1+1.
Alcatel-Lucent 1665 DMX also supports non-revertive bidirectional 1+1 switching to enable interworking between Alcatel-Lucent 1665 DMX and Ciena Core Director.
Path protection rings feed a SONET payload (STS or virtual tributary [VT]) from the ring entry point, simultaneously in both rotations of the ring, to the signal's ring exit point. The node that terminates the signal from the ring monitors both ring rotations and is responsible for selecting the signal that has the highest quality based on LOS, LOF, and path BER performance. On pass-through paths, all detected hard failures (LOS, LOF, line AIS, or STS-1 path AIS) result in VT AIS insertion in the outgoing signals. This allows the terminating node to be aware of the failure and to switch to protection. Protection switching is completed within 50 milliseconds of failure detection.
Under normal conditions, both incoming SONET path signals to the switch selection point are of high quality, and the signal can be selected from either ring. A failure or transmission degradation on one of the rings requires that the other ring path be selected. Alcatel-Lucent 1665 DMX provides nonrevertive switching. When and if the critical service should revert to a particular ring, a manual path protection switching command allows switching back to the original path for ease of ring maintenance in non-revertive applications.
On low-speed SONET optical interfaces (OC-3/12/48), UPSR is optional and protection switching is provisionable (UPSR or 1+1) on a per-line basis.
Alcatel-Lucent 1665 DMX supports OC-192 and OC-48 2-fiber BLSR protection groups in the high-speed or low-speed slots, with STS-n cross-connectivity between any BLSR working tributary and the tributaries of all supported interfaces. This includes BLSR to BLSR cross-connections. Limited support is also provide for VT cross-connections (large fabric non-VLF mains only) and Extra Traffic). BLSR through cross-connections are also supported. However, cross-connections between different tributaries (timeslots) on the east and west ports of the ring are not supported. The BLSR ring map may be provisioned manually or automatically discovered. The squelch map entries may be manually provisioned or automatically generated. The BLSR switching is GR-1230-CORE complaint. However, external switch requests that must be signaled on the DCC channels are not supported.
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