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IEEE 802.1ag (also CFM) (''IEEE Standard for Local and Metropolitan Area Networks Virtual Bridged Local Area Networks Amendment 5: Connectivity Fault Management'') is a standard defined by IEEE. It defines protocols and practices for OAM (Operations, Administration, and Maintenance) for paths through 802.1 bridges and local area networks (LANs). It is an amendment to IEEE 802.1Q-2005 and was approved in 2007.〔(Status of IEEE 802 Standards )〕 IEEE 802.1ag is largely identical with ITU-T Recommendation Y.1731, which additionally addresses performance monitoring.〔(Ethernet Service OAM- Relevant Standards )〕 The standard: *Defines maintenance domains, their constituent maintenance points, and the managed objects required to create and administer them *Defines the relationship between maintenance domains and the services offered by VLAN-aware bridges and provider bridges *Describes the protocols and procedures used by maintenance points to maintain and diagnose connectivity faults within a maintenance domain; *Provides means for future expansion of the capabilities of maintenance points and their protocols ==Definitions== The document defines various terms: ;Maintenance Domain (MD): Maintenance Domains are management space on a network, typically owned and operated by a single entity. MDs are configured with ''Names'' and ''Levels'', where the eight levels range from 0 to 7. A hierarchical relationship exists between domains based on levels. The larger the domain, the higher the level value. Recommended values of levels are as follows: *Customer Domain: Largest (e.g., 7) *Provider Domain: In between (e.g., 3) *Operator Domain: Smallest (e.g., 1) ;Maintenance Association (MA): Defined as a "set of MEPs, all of which are configured with the same MAID (Maintenance Association Identifier) and MD Level, each of which is configured with a MEPID unique within that MAID and MD Level, and all of which are configured with the complete list of MEPIDs.” ;Maintenance association End Point (MEP): Points at the edge of the domain, define the boundary for the domain. A MEP sends and receives CFM frames through the relay function, drops all CFM frames of its level or lower that come from the wire side. ;Maintenance domain Intermediate Point (MIP): Points internal to a domain, not at the boundary. CFM frames received from MEPs and other MIPs are cataloged and forwarded, all CFM frames at a lower level are stopped and dropped. MIPs are passive points, respond only when triggered by CFM trace route and loop-back messages. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「IEEE 802.1ag」の詳細全文を読む スポンサード リンク
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