User Manual UMN:CLIV5812G2618.4.2 Loss of Test Packet (LOTP)ERP recognizes the Link Failure using Loss of Test Packet (LOTP) mechanism. RM Nodeperiodically sends periodic ―RM Test Packet‖ message. The state of LOTP means that―RM Test Packet‖ message does not return three consecutive times to RM node throughEthernet Ring. If RM node receives its ―RM Test Packet‖ message through Ethernet Ring,it continues to block its secondary port.You can configure the interval for sending ―RM Test Packet‖ message.8.4.3 ERP Shared LinkSharing a link between two ERP rings allows the two nodes adjacent to the link to becommon to the two rings. Sharing one link between two rings would create a ―super loop‖if that link failed. To prevent the super loop, two ERP domains should have differentpriorities. This concept is called ―ERP ring priority‖. When a link is shared by two or morerings, one RM node with the highest priority is responsible to protect failures of the sharedlink. Two normal nodes of a shared link belong to both ERP domains. The control packets(TPs) can be transmitted from the lower priority domain to higher priority domain only.Fig. 8.33 shows the example of ring interconnection using one shared link.Fig. 8.33 Shared LinkERP shared link environment has the following requirements, so you should keep in mindthem before configuring ERP ring topology with a shared link.• A port adjacent to the shared link should not be blocked. It means that a shared linkthat is used as the one of the secondary ports of a RM node.• If there are two ERP domains with a single shared link, you should specify differentpriority of ERP domains.• The higher priority domain should include all protected and control VLANs of thelower priority domain to protect and manage the lower priority ring more effectively.!
