Operation and behavior conferment with Annex B of ITU.T G.841 can be configured for an APS group. Characteristics of this mode include are the following:
Annex B operates in non-revertive bidirectional switching mode only as defined in G.841.
Annex B operates with 1+1 signaling, but 1:1 data path whereby data is transmitted on the active link only.
K bytes are transmitted on both circuits.
Because the request/reverse-request nature of an Annex B switchover, the data outage is longer than a typical (non Annex B single chassis) APS switchover. IMA bundles that are protected with Annex B APS have to resynchronize after a switchover. It is recommended to use maintenance commands (tools>perform>aps…) for planned switchovers (not MDA or IOM shutdown) to minimize the outage.