Ethernet Ring Protection Switching (ERPS)
ERPS is a ring protection scheme for Ethernet networks, and is supported on BTI 7000 Series, BTI Service Access 800 Series, and BTI 700 Series equipment. ERPS is intended for ring topologies and is typically more efficient than spanning tree protocols, but requires configuration every time you add or remove nodes or Ethernet services from the ring.
The network operator creates the ERPS service directly on the network element using either the proNX 900 or the CLI, and can use PSM to view the service graphically. PSM automatically discovers and displays ERPS services in the network but does not currently support creating ERPS services.
Visualizing an ERPS Service
Use this procedure to view the ERPS service and its states.
Under normal (non-failure) conditions, the ERPS service blocks the RPL link to prevent looping of traffic for the Ethernet services it is protecting. On link failure, the ERPS service enables the blocked port to allow traffic from those Ethernet services to continue to flow.
- In the Network tree view, select the desired
The ERPS service view opens in the main map window. If PSM is configured to show the ERPS link icons (Setting service display options), a green is displayed to indicate the RPL link being blocked.
- Right click the service view and select Show Connected
The ERPS service view is expanded to show the ports.
- Hover over the network elements to see information on
the ERPS service.
For the purposes of illustration, the mouse-over information for two network elements is shown simultaneously.
- Hover over the NNI ports to see ERPS information for
the NNI ports.
For the purposes of illustration, the mouse-over information for two NNI ports are shown simultaneously.
The same ERPS state information can be viewed from the Details tab in the UNI/NNI Ports pane of the Ethernet Service Activation window. Simply double-click on an existing ERPS service in the Network tree view and select the Details tab.
Effect Of Link Failure on ERPS States
If a link goes down, the RPL port becomes unblocked and the ERPS states change to show that it is in protecting mode. If PSM is configured to show the ERPS link icons (Setting service display options), a red is displayed to indicate the failed link, and a green is displayed on the RPL link to show that it is passing traffic.
For the purposes of illustration, the mouse-over information for various elements and ports are shown simultaneously.
Viewing the ERPS Services Table
Use this procedure to view the ERPS services table.
The ERPS services table displays information on all ERPS services running in the network.
- Select View >Ethernet >ERPS.
The ERPS services table opens in the main Map window. The table shows the ERPS services in the network along with their port states and other information.
Adding VLANs to an ERPS Ring
Use this procedure to add VLANs to a node in an ERPS ring.
PSM can be used to add VLAN IDs to a node in an ERPS ring. The typical use case for this procedure is to help with ERPS node insertion. Node insertion refers to breaking the NNI between two adjacent nodes in a ring, and reattaching the same NNI ports to a new node.
When a node is inserted into an ERPS ring, the list of VLANs must be configured on the new node, as follows:
Associate the list of VLANs to the ERPS ring NNIs on the new node. This is not needed if GVRP is enabled on the ring.
Add the list of VLANs to the ERPS protected VLAN list on the new node.
Create the Ethernet services represented by these VLANs on the new node.
This procedure performs the above 3 tasks and runs an audit of the ERPS ring. The audit checks to make sure the existing configuration is consistent across all the nodes, and highlights any inconsistencies that it finds. Although the audit results are purely informational, and do not block the user from proceeding, you should examine the results for potential issues.
Additionally, PSM creates MIPs on the ERPS ring NNIs on the new node if MIPs have been configured on the ERPS ring NNIs on the existing nodes.
The following are the constraints for this procedure:
This procedure should only be used on non-interconnect nodes. A non-interconnect node is a node that is not simultaneously part of a main ring and a sub-ring.
This procedure should only be used when there is a single ERPS ring on the physical topology. Running this procedure in a configuration where there are multiple ERPS rings on the same physical ring is not supported.
This procedure should only be run when a single node is inserted. When inserting multiple nodes in a ring, you should insert and repair one node at a time.
This procedure supplements the ERPS node insertion procedures on the network elements. Refer to the ERPS node insertion procedures in the respective documentation for the different network elements for more details.
- Select the desired ERPS service in the tree view.
- In the Ethernet services topology window, identify the
node that you want to add the VLANs to.
This is typically the newly inserted node.
- Right click
that node and select Repair VLANs.
PSM audits the ERPS service, treats the existing nodes as the baseline, and prepares to configure the selected node to be consistent with the baseline. The audit results and the list of VLANs to be added are presented. For example:
Here is an example of an audit that has uncovered underlying issues:
You can use this procedure purely to audit the ERPS ring.
- Add the VLANs to the selected node.
If the audit shows that the ERPS ring is healthy, select OK to add the VLANs to Repair list to the selected node.
If the audit shows issues with the existing ERPS ring configuration, select Cancel, fix the issues, and repeat 3.
You are advised, but not required, to fix the audit issues before selecting OK to add the VLANs.
Once you click OK, PSM associates the list of VLANs to the ERPS ring NNIs on the selected node, adds the list of VLANs to the protected VLAN list for the ERPS service on the selected node, creates the Ethernet services represented by these VLANs, and finally, creates the MIPs as necessary.