Siemens S223, S323 user manual Ethernet Ring Protection ERP, ERP Operation

User Manual	UMN:CLI
SURPASS hiD 6615 S223/S323 R1.5

8.9Ethernet Ring Protection (ERP)

The ERP is a Siemens protection protocol and procedure to protect Ethernet ring topolo- gies. It is a fast failure detection and recovery so that it decreases the time to prevent Loop under 50ms.

The main characteristics of the ERP are the follows:

•It required no additional underlying protection mechanism within the ring configuration, the complete functionality is implemented on the interface units of the system and does not require additional dedicated hardware which may raise network complexity and costs.

•It is a unique robustness functionality which runs on every network element involved in the ring configurations. It means each system is active part of the ring protection mechanism. Therefore, it guarantees a maximum of 50 ms to switch over towards a new configuration after link or system failures.

•ERP and STP cannot be configured at once.

8.9.1ERP Operation

Ethernet Ring Protection (ERP) is a concept and protocol optimized for fast failure detec- tion and recovery on Ethernet ring topologies. The Protection of fast failure detection and recovery occurs on RM Node. An Ethernet ring consists of two or more switches. One of the nodes on the ring is designated as redundancy manager (RM) and the two ring ports on the RM node are configured as primary port and secondary port respectively.

The RM blocks the secondary port for all non-control traffic belongs to this ERP domain. Here, if Line failure occurs, the Nodes detecting Link Failure transmit Link Down message and Link Failure port becomes Blocking status. When the RM nodes receive this link- down message, it immediately declares failed state, and opens the logically blocked pro- tected VLANs on the secondary port. Then, Ethernet Ring restarts the communication.

The following is ERP operation when Link Failure occurs.

3.Nodes detecting Link Failure Transmit Link Down message

3.Nodes detecting Link Failure Transmit Link Down message

Normal Node Normal Node

2. Link Failure

Normal Node

S

P

RM Node

1. Secondary port of RM node is

blocking in Normal state

Fig. 8.35 Ethernet Ring Protocol Operation in Failure State

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