3-6Ring recoveryThe master node may find the ring is restored after a period of time after the ports belonging to theRRPP domain on the transit nodes, the edge nodes, or the assistant-edge nodes are brought up again.A temporary loop may arise in the data VLAN during this period. As a result, broadcast storm occurs.To prevent temporary loops, non-master nodes block them immediately (and permit only the packets ofthe control VLAN to pass through) when they find their ports accessing the ring are brought up again.The blocked ports are activated only when the nodes are sure that no loop will be brought forth bythese ports.Broadcast storm suppression mechanism in a multi-homed subring in case of SRPT failureAs shown in Figure 3-5, Ring 1 is the primary ring, and Ring 2 and Ring 3 are subrings. When the twoSRPTs between the edge node and the assistant-edge node are down, the master nodes of Ring 2and Ring 3 will open their respective secondary ports, and thus a loop among Device B, Device C,Device E, and Device F is generated. As a result, broadcast storm occurs.In this case, to prevent generating this loop, the edge node will block the edge port temporarily. Theblocked edge port is activated only when the edge node is sure that no loop will be brought forth whenthe edge port is activated.Load balancingIn a ring network, maybe traffic of multiple VLANs is transmitted at the same time. RRPP canimplement load balancing for the traffic by transmitting traffic of different VLANs along different paths.By configuring an individual RRPP domain for transmitting the traffic of the specified VLANs (referredto as protected VLANs) in a ring network, traffic of different VLANs can be transmitted according todifferent topologies in the ring network. In this way, load balancing is achieved.As shown in Figure 3-6, Ring 1 is configured as the primary ring of Domain 1 and Domain 2, which areconfigured with different protected VLANs. Device A is the master node of Ring 1 in Domain 1; DeviceB is the master node of Ring 1 in Domain 2. With such configurations, traffic of different VLANs can betransmitted on different links, and thus, load balancing is achieved in a single-ring network.RRPP ring groupIn an edge node RRPP ring group, only an activated subring with the lowest domain ID and ring ID cansend Edge-Hello packets. In an assistant-edge node RRPP ring group, any activated subring that hasreceived Edge-Hello packets will forward these packets to the other activated subrings. With an edgenode RRPP ring group and an assistant-edge node RRPP ring group configured, only one subringsends and receives Edge-Hello packets, thus reducing CPU workload.As shown in Figure 3-5, Device B is the edge node of Ring 2 and Ring 3, and Device C is theassistant-edge node of Ring 2 and Ring 3. Device B and Device C need to send or receive Edge-Hellopackets frequently. If more subrings are configured or load balancing is configured for more multipledomains, Device B and Device C will send or receive a mass of Edge-Hello packets.To reduce Edge-Hello traffic, you can assign Ring 2 and Ring 3 to an RRPP ring group configured onthe edge node Device B, and assign Ring 2 and Ring 3 to an RRPP ring group configured on Device C.After such configurations, if all rings are activated, only Ring 2 on Device B sends Edge-Hello packets.Typical RRPP NetworkingHere are several typical networking applications.
