Specifications

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Chapter 4 Configuring the Cisco MWR 2941 Router Using the CLI
Configuration Sequence
Figure 4-2 Ethernet CFM Maintenance Domain
A unique maintenance level in the range of 0 to 7 is assigned to each domain by a network administrator.
Levels and domain names are useful for defining the hierarchical relationship that exists among
domains. The hierarchical relationship of domains parallels the structure of customer, service provider,
and operator. The larger the domain, the higher the level value. For example, a customer domain would
be larger than an operator domain. The customer domain may have a maintenance level of 7 and the
operator domain may have a maintenance level of 0. Typically, operators would have the smallest
domains and customers the largest domains, with service provider domains between them in size. All
levels of the hierarchy must operate together.
Domains should not intersect because intersecting would mean management by more than one entity,
which is not allowed. Domains may nest or touch but when two domains nest, the outer domain must
have a higher maintenance level than the domain nested within it. Nesting maintenance domains is useful
in the business model where a service provider contracts with one or more operators to provide Ethernet
service to a customer. Each operator would have its own maintenance domain and the service provider
would define its domain—a superset of the operator domains. Furthermore, the customer has its own
end-to-end domain which is in turn a superset of the service provider domain. Maintenance levels of
various nesting domains should be communicated among the administering organizations. For example,
one approach would be to have the service provider assign maintenance levels to operators.
CFM exchanges messages and performs operations on a per-domain basis. For example, running CFM
at the operator level does not allow discovery of the network by the higher provider and customer levels.
Network designers decide on domains and configurations. Figure 4-3 illustrates a hierarchy of operator,
service provider, and customer domains and also illustrates touching, intersecting, and nested domains.
Port interior to domain
Maintenance
domain
Port at edge of domain
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