How is the primary worker aware of the backup worker death?

If the SCOS backup worker on CE 2 dies, then the matching SCOS primary worker on CE 1 will see it by detecting a hang up of its SCTP communications with the dead backup worker. The CE 1 SCOS primary worker will then re-connect to the SCOS process manager on CE 2 (sctp_connect), which in turn will start a new CE 2 SCOS backup worker that will be able to exchange data again with the CE 1 SCOS primary worker.