Web Management Guide-R05

Chapter 13 | Basic Administration Protocols
Connectivity Fault Management
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association) against those found through continuity check messages. Fault
verification is supported using loop back messages, and fault isolation with link
trace messages. Fault notification is also provided by SNMP alarms which are
automatically generated by maintenance points when connectivity faults or
configuration errors are detected in the local maintenance domain.
Key Components of CFM
CFM provides restricted management access to each Service Instance using a
structured conceptual network based on these components:
◆ A Maintenance Domain defines a part of the network controlled by a single
operator, and supports management access to the domain through Domain
Service Access Points (DSAPs) configured on the domain boundary, as well as
connectivity testing between these DSAPs.
◆ A Maintenance Association (MA) contains the DSAPs for an individual Service
Instance. DSAPs are the primary maintenance points used to monitor
connectivity across a maintenance domain, and are the entry points to the
paths which interconnect the access points allocated to a service instance.
◆ A Maintenance Level allows maintenance domains to be nested in a
hierarchical fashion, providing access to the specific network portions required
by each operator. Domains at lower levels may be either hidden or exposed to
operators managing domains at a higher level, allowing either course or fine
fault resolution.
◆ Maintenance End Points (MEPs) which provide full CFM access to a Service
Instance (i.e., a specific MA), and Maintenance Intermediate Points (MIPs) which
are passive entities that merely validate received CFM messages, or respond to
link trace and loop back requests. MIPs are the interconnection points that
make up all possible paths between the DSAPs within an MA, and may also
include interconnection points in lower-level domains if exposed by CFM
settings.