Connectivity Fault Management (CFM) as per IEEE 802.1ag / ITU-T Y.1731 is a collection of protocols and tools for OAM on Layer 2. CFM is used for monitoring and fault analysis in LANs, bridges, or Ethernet-based WANs.
The protocols particularly enable providers or operators and administrators of Ethernet connections to proactively monitor these connections or analyze them in case of faults.
LCOS supports the following functions:
- Continuity Check Messages (CCM): Regular status messages are exchanged to monitor the availability of network elements.
- Loopback: Loopback messages can be sent and returned by the remote side (ethping / Layer 2). This function is analogous to the ICMP-based Ping on Layer 3. Both Ethernet unicast and multicast addresses are supported.
- Linktrace: Linktrace messages can be sent, which are returned by the remote side and responded to by network elements along the path (Layer 2). This function is analogous to the ICMP-based Traceroute on Layer 3.
The CCM, Loopback, and Linktrace functions can be used independently, meaning Loopback and Linktrace can be utilized even without regular CCM messages.
Additionally, LCOS supports the following functions from ITU-T Y.1731:
- Reception and status display of ETH-AIS (Alarm Indication Signal)
- Reception and status display of ETH-LCK (Ethernet Locked Signal)
- Reception and processing of ETH-RDI (Remote Defect Indication)
