Siemens S223 - Manual (Page 265)

User Manual UMN:CLI
SURPASS hiD 6615 S223/S323 R1.5
A50010-Y3-C150-2-7619 265
8.9 Ethernet 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.
8.9.1 ERP 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 RM Node
P
S
1. Secondary port of RM node is
blocking in Normal state
Fig. 8.35 Ethernet Ring Protocol Operation in Failure State