CANOGA PERKINS 9145EMP NID Software Version 4.0 - Manual (Page 143)

9145EMP NID Software User’s Manual Service OAM
Service OAM
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11.1.1 SOAM Entities
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 11-2.
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 the 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 an EVC record, 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.
• 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.
11.1.2 Logical Positioning of MEPs and MIPs
Untagged down MEPs can be configured on each physical User port. On the Network side, if
LAG is disabled, an untagged down MEP can be configured on the active network port. If LAG is
enabled, a single untagged down MEP can be configured on the LAG.
Figure 11-1 describes the logical positioning of MEPs in the 9145EMP NID system. The NID
sports the following endpoints, i.e., MEPs: