Basic CFD concepts

A maintenance domain (MD) defines the network or part of the network where CFD plays its role. An MD is identified by its MD name.

A maintenance association (MA) is a part of an MD. You can configure multiple MAs in an MD as needed. An MA is identified by the MD name + MA name.

An MA serves the specified VLAN or no VLAN. An MA that serves a VLAN is considered to be carrying VLAN attribute. An MA that serves no VLAN is considered to be carrying no VLAN attribute.

An MP is configured on a port and belongs to an MA. MPs include the following types: maintenance association end points (MEPs) and maintenance association intermediate points (MIPs).

MEPs define the boundary of the MA. Each MEP is identified by a MEP ID.

MEPs include inward-facing MEPs and outward-facing MEPs:

• An outward-facing MEP sends packets to its host port.

• An inward-facing MEP does not send packets to its host port. Rather, it sends packets to other ports on the device.

A MIP is internal to an MA. It cannot send CFD packets actively, but it can handle and respond to CFD packets. MIPs are automatically created by the device. By cooperating with MEPs, a MIP can perform a function similar to ping and traceroute.

A MEP list is a collection of local MEPs allowed to be configured and the remote MEPs to be monitored in the same MA. It lists all the MEPs configured on different devices in the same MA. The MEPs all have unique MEP IDs. When a MEP receives from a remote device a continuity check message (CCM) carrying a MEP ID not in the MEP list of the MA, it drops the message.

The local device must send CCM messages carrying the Remote Defect Indication (RDI) flag bits. Otherwise, the peer device cannot sense certain failures. When a local MEP has not learned all remote MEPs in the MEP list, the MEPs in the MA might not carry the RDI flag bits in CCMs.