Supported Platforms
Understanding Fault Isolation and Detection in a PBB using Connectivity Fault Management for MX Series Routers
Connectivity Fault Management (CFM) provides fault isolation and detection over large Layer 2 networks which may span several service provider networks. Provider backbone bridging (PBB) extends Layer 2 Ethernet switching to provide enhanced scalability, QoS features, and carrier-class reliability in service provider networks. CFM is used with PBB to support that carrier-class reliability. CFM is used to monitor, isolate and verify the faults in a network. The JUNOS Software implementation of PBB supports the IEEE 802.1ah (PBB) and IEEE 802.1ag (CFM) standards.
 | Note: PBB is supported only on MX Series routers with Dense Port Concentrators (DPCs). PBB is not supported on MX Series routers with Modular Port Concentrators (MPCs). |
PBB defines an architecture and bridge protocols for connecting multiple provider bridge networks (PBN). A Provider Backbone Bridged Network (PBBN) comprises a set of Backbone Edge Bridges (BEBs) interconnected by some or all of the service VLANs (S-VLANs) supported by a Provider Bridged Network (PBN). S-VLANs are first encapsulated with an I-TAG to uniquely identify the service with PBBN and then are encapsulated within a B-VLAN to be carried over the PBBN core.
CFM uses a set of protocols (Continuity Check, Linktrace and Loopback) for operation, administration and management (OAM) to provide fault isolation and detection. OAM is enabled in a PBN or PBBN by customers, service providers, and network operators in their respective maintenance domains. The OAM operations in PBN and PBBN can coexist and are independent of each other.
In the OAM protocol, the end nodes in maintenance domains are called maintenance end points (MEPs) and initiate OAM processes.
Intermediate nodes respond to these OAM processes and are called maintenance intermediate points (MIPs). MIPs are configured for the I-Component of the BEB. Using MEPs and MIPs, CFM provides end-to-end connectivity in the S-VLAN.
To configure a MEP or a MIP, include the mep or mip statement at the [edit protocols oam ethernet connectivity-fault-management maintenance-domain domain-name maintenance-association] hierarchy level.
| Note: UP MEPs for S-VLANs within an I-component are not supported. |
To enable the continuity check protocol to provide fault detection and notification, include the continuity-check statement at the [edit protocols oam ethernet connectivity-fault-management maintenance-domain domain-name maintenance-association] hierarchy level.
The Linktrace protocol provides path discovery and fault verification. Linktrace is enabled by default and can be used whenever a MEP is configured.
The Loopback protocol (modeled on the standard IP ping) is used to perform fault verification and isolation after a fault is detected. Loopback, like Linktrace, is enabled by default and can be used whenever a MEP is configured.
