ANSI T1.105.01-2000 pdf download Synchronous Optical Network (SONET) – Automatic Protection Switching
4.1.6 automatically initiated command: An APS request that is initiated by any one of the following:
(1) SONET line performance criteria,
(2) local equipment performance criteria, or (3) received bridge requests.
4.1.7 auto-provisioning: The assignment of values to parameters within a network element, without those values being specifically entered externally by a user.
4.1.8 bidirectional protection switching: In bidirectional protection switching, for a unidirectional fail- ure, both the affected and the unaffected directions switch to protection. For example, in 1 + 1 protection, though an APS channel is not required to perform the protection switch, an APS channel would be required for bidirectional operation to notify the transmit end that the receive end has switched, so that the other direction can be switched as well. Bidirectional operation in general requires an APS channel.
4.1.9 bit interleaved parity N (BIP-N): A method of error monitoring. If even parity is used, an N-bit code is generated by the transmitting equipment over a specified portion of the signal in such a manner that the first bit of the code provides even parity over the first bit of all N-bit sequences in the covered portion of the signal, the second bit provides even parity over the second bits of all N-bit sequences within the specified portion, and so on. Even parity is generated by setting the BIP-N bits so that there are an even number of 1s in each of all N-bit sequences including the BIP-N.
4.1.10 bridge: The action of transmitting identical traffic (SPE contents) on both the working and protection channels.
4.1.11 concatenated synchronous transport signal level N (STS-Nc): A signal constructed by con- catenating the envelope capacities of N STS-1s to carry a STS-Nc SPE which transports a superrate signal. These STS-1s shall be transported as a single entity.
4.1.12 controller failure: The condition during which a node is no longer able to correctly operate the APS protocol but still generates a correctly formatted SONET frame.
4.1.13 extra traffic: Traffic that is carried over the protection channels when that capacity is not used for the protection of working traffic. Extra Traffic is not protected. Whenever the protection channels are re- quired to protect the working traffic, the Extra Traffc is preempted. Ring interworking on protection is considered Extra Trffic.
4.1.14 externally initiated command: An APS request that is initiated by either an OS or craftsperson.
4.1.15 head-end: The node executing a bridge. Note that a node functions as a head-end and a tail-end for a bidirectional switch for the same span.
4.1.16 line: A transmission medium, together with the associated equipment, required to provide the means of transporting information between two Network Elements (NEs), one of which originates the line signal and the other terminates the line signal (see figures 2 and 3 in T1.105).