Maintenance Domain (MD)

A maintenance domain (MD) is the highest configuration context in which a CFM service resides. The MD is a collection of network devices, typically owned and operated by a single organization. Management of devices within a domain falls under the control of that single organization. Domains must be contiguous, such that all the devices belonging to a domain have uninterrupted network connectivity with each other. Domains may be nested or adjacent, but can not share network devices with other domains. Domains are intended to provide connectivity to systems outside of the domain. All devices associated with a monitored service must belong to the MD. The monitored service is configured within the MD. MDs are uniquely identified by an MD Name.

An MD is assigned a level relative to other MDs a monitored service passes through. The monitored service must belong to an MD with a higher level than all other MDs that the monitored service passes through. The CCM will not be allowed to enter an MD with a higher level than the MD that initiated the CCM.

Maintenance Domain Overview displays how each administratively controlled segment of the network is configured within its own MD in a service provider context made up of:

• A customer equipment maintenance domain mdCE1
• A service provider maintenance domain mdSP1
• Two operator maintenance domains mdOp1 and mdOP2

The above figure displays a typical MD domain configuration in a service provider context. The end-points of the monitored service (CE Device 1 and CE Device 2) belong to the customer equipment domain mdCE1. The monitored service is a VLAN these end-points belong to. The MD to which the monitored service devices belong must encapsulate any MDs the monitored service passes through from one end-point of the service to the other end-point. This encapsulation is accomplished by the MD level. The customer equipment MD is assigned the highest MD level in our example, assuring that CCMs will be allowed to pass between the monitored service end-points. The encapsulated MDs can belong to such entities as service providers and network operators as shown here, or they can be segmented parts of your own network.

In our example, the monitored service belongs to MD mdCE1 and passes through mdSP1, mdOp1, and mdOp2 before reaching end-point CE Device 2 which belongs to MD mdCE1.

An MD constrains CFM traffic flows. CFM traffic flows of the MD owner and can transparently flow through any encapsulated MD with a lower MD level. mdCE1 CFM traffic flows pass through all the displayed MDs. mdSP1 traffic flows pass through mdOp1 and mdOp2, but are prevented from transiting into mdCE1. mdOP1 and mdOP2 CFM traffic is restricted to its own MD. This containment of traffic flows prevents unintended information flow between MDs.