Brocade Communications Systems Brocate Ethernet Access Switch 6910 - Manual (Page 1020)

970 Brocade 6910 Ethernet Access Switch Configuration Guide
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Connectivity Fault Management
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Connectivity Fault Management
Connectivity Fault Management (CFM) is an OAM protocol that includes proactive connectivity
monitoring using continuity check messages, fault verification through loop back messages, and
fault isolation by examining end-to-end connections between provider edge devices or between
customer edge devices.
CFM is implemented as a service level protocol based on service instances which encompass only
that portion of the metropolitan area network supporting a specific customer. CFM can also provide
controlled management access to a hierarchy of maintenance domains (such as the customer,
service provider, and equipment operator).
This switch supports functions for defining the CFM structure, including domains, maintenance
associations, and maintenance access points. It also supports fault detection through continuity
check messages for all known maintenance points, and cross-check messages which are used to
verify a static list of remote maintenance points located on other devices (in the same
maintenance 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.