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9145E NID Software User’s Manual Service OAM

Service OAM

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11.1.1 SOAM Entities

In order to execute the Service OAM procedures, specific entities must be configured at the

network and NID level. Some of those entities are shown in Figure 11-3.

The SOAM entities are:

• Maintenance Domain: A maintenance domain (MD) is a managed part of a network. It is

bounded by a set of ports on which maintenance association end points (MEPs) are

instantiated, forming one or more maintenance associations at a particular level. An MD

is identified by an MD level value, assigned by the network administrator. The MD level is

used to define the hierarchical relationship between domains. Typically, higher level

domains are closer to the customer, while lower level domains correspond to service pro-

viders and physical level. Domains cannot intersect or overlap, but they can touch or

nest. CFM exchanges messages and performs operations on a per-domain basis.

• Maintenance Association: A maintenance association (MA) is a logical connection

between MEPs. An MA is defined by a set of MEPs configured with identical values of

maintenance association identifiers (MAID). While MDs are strictly logical entities, an MA

represents the association of an administrative domain with a specific Ethernet transport

entity. For example, an MA can be attached to a VLAN or set of VLANs, or be VLAN

unaware for low-level domains such as link-level domains.

• Maintenance Entity Group: The concepts of maintenance domain and maintenance

association are merged in a single entity called a Maintenance Entity Group in Y.1731. As

such, a MEG is a logical connection between several MEPs that are defined as the part of

the same administrative domain and have the same level.

• Maintenance Association End Point: A MEP is an entity that is instantiated in a NID

port. A MEP belongs to one MA or MEG and represents the boundaries of that specific

domain. A MEP can monitor the traffic that is transmitted and received from a port

towards the wire (a DOWN MEP), or it can monitor the traffic transmitted and received

from the forwarding engine of a device (an UP MEP). Only a MEP can initiate SOAM

requests and prevent leaking of OAM messages between domains. Figure 11-1

describes the positioning of UP and DOWN MEPs on the USER port of a 9145E NID, and

the corresponding monitoring traffic.

• Maintenance Intermediate Point: A maintenance intermediate point (MIP) is an OAM

entity that is instantiated in a NID port and a Management Domain or Management Entity

Group. A MIP is a passive Service OAM entity. It receives Service OAM messages and

responds to the originating MEP. A MIP responds to linktrace and loopback messages

only. MIPs are internal to a domain, therefore they cannot be located at the domain

boundary. MEPs and MIPs are generically called Maintenance Points (MPs). If a MEP or

MIP is associated with a MEG, it is executing Y.1731 procedures. If it is associated with

an MA or MD, it is executing 802.1ag procedures.

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Canoga-perkins 9145E NID Software Version 4.10 Manuel d'utilisateur Page 210