ERPS structure
Figure 24: ERPS ring structure
Rings
ERPS rings can be divided into major rings and subrings. An ERPS network consists of one major ring or multiple major rings, and multiple subrings. By default, a ring is a major ring. You can configure a ring as a subring manually.
As shown in Figure 24, a major ring is a closed ring formed by Device A, Device B, Device C, and Device D. A subring is an open ring formed by the link Device C<—>Device E<—>Device F<—>Device D.
Nodes
ERPS nodes include owner nodes, neighbor nodes, interconnection nodes, and normal nodes.
The owner node and neighbor node block and unblock ports on the ring protection link (RPL) to prevent loops and switch traffic. An RPL connects an owner node and a neighbor node.
Interconnection nodes connect different rings. Interconnection nodes reside on subrings and forward service packets but not protocol packets.
Normal nodes forward both service packets and protocol packets.
As shown in Figure 24, on the major ring, Device A is the owner node and Device B is the neighbor node. On the subring, Device E is the owner node and Device F is the neighbor node. Devices C and D are interconnection nodes.
Ports
Each node consists of two ERPS ring member ports: Port 0 and port 1. ERPS ring member ports have the following types:
RPL port—Port on an RPL link.
Interconnection port—Port that connects a subring to a major ring.
Normal port—Default type of a port that forwards both service packets and protocol packets.
As shown in Figure 24, ports A1, B1, E1, and F1 are RPL ports. Ports C3 and D3 are interconnection ports. Other ports are normal ports.
Instances
An ERPS ring supports multiple ERPS instances. An ERPS instance is a logical ring to process service and protocol packets. Each ERPS instance has its own owner node and maintains its own state and data. An ERPS instance is uniquely identified by the ring ID and VLAN ID of ERPS packets. The ring ID indicates the ring of ERPS packets. It can be represented by the last byte in the destination MAC address of the packets. The VLAN ID indicates the ERPS instance of the packets.