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.
RPL
An ERPS ring is composed of many nodes. Some nodes use ring protection links (RPLs) to prevent loops on the ERPS ring. As shown in Figure 24, the link between Device A and Device B and the link between Device E and Device F are RPLs.
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 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.