Method and device for operating a network and communication system comprising such device

A method of operating a network, which comprises:

• providing the network with:
• a plurality of network elements connected via a ring;
• wherein a first segment comprises a non-Ethernet connection and a second segment is an Ethernet connection;
• the ring including at least one first segment and at least one second segment;
• wherein one network element of the network elements is a ring master having a primary port and a secondary port;
• wherein a network element of the at least one second segment runs an Ethernet ring protection mechanism using test packets;
• the method which comprises the following steps:
• detecting a failure of at least one of the at least one first segment by the ring master;
• unblocking the secondary port of the ring master;
• sending a first message by the ring master via the primary port and via the secondary port;
• responding, with each network element that received the first message, with an acknowledge message and forwarding the first message to a next network element;
• if a network element does not receive an acknowledge message, entering a pre-forwarding state with the network element, the pre-forwarding state being a state in which the network element blocks all traffic except the test packets and waits to switch over to normal operation;
• in the pre-forwarding state, blocking a port of the network element toward the network element that did not send the acknowledge message;
• sending a second message to the ring master with the network element entering the pre-forwarding state;
• after recovery of the failure, blocking the secondary port of the ring master and sending a third message via the primary port and via the secondary port;
• and
• upon receiving the third message, switching each network element residing in the pre-forwarding state to the normal operation.