Cisco Catalyst 4500 Series, Руководство по настройке программного обеспечения

Страница: 1906 / 2086

76-2
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Chapter 76 Configuring Y.1731 (AIS and RDI)
About Y.1731
About Y.1731
These sections contain conceptual information about Y.1731:
•
Server MEP, page 76-2
• Alarm Indication Signal, page 76-2
•
Ethernet Remote Defect Indication, page 76-3
The advent of Ethernet as a metropolitan and WAN technology imposes a new set of Operations,
Administration, and Maintenance (OAM) requirements on Ethernet's traditionally Enterprise-oriented
functions. The expansion of this technology into the larger and more complex wider user base makes
operational management of link uptime crucial. Isolating and responding to failures quickly directly
affects the competitiveness of the service provider.
Server MEP
A Server MEP is a combined function of the server layer termination function and the server and ETH
adaptation function. It issues frames with ETH-AIS information upon detecting a defect at the Server
layer by the server layer termination function or the adaptation function.
A Virtual MEP represents the logical termination point of Connectivity Fault Management (CFM) MAs
defined at the link or transport layer. A server MEP runs or is defined at Maintenance Level -1. For
example, you could associate an outward-facing Server MEP with each termination point of IEEE
802.3ah OAM, or with each termination point of MPLS PW OAM.
Alarm Indication Signal
ETH-AIS allows you to suppress alarms when defects are detected at the server (sub) layer. Because of
STP’s ability to restore, you would not expect to apply ETH-AIS in the STP environments. For the
Catalyst 4500 Metro switch, an administrator can enable and disable AIS in the STP environment.
You can enable or disable transmission of frames with ETH-AIS information on an MEP (or on a Server
MEP).
You also can issue frames with ETH-AIS information at the client Maintenance Level by a MEP,
including a Server MEP upon detecting defect conditions.
The defect conditions may include:
•
Signal fail conditions with ETH-CC enabled
• AIS condition with ETH-CC disabled
For multipoint ETH connectivity, a MEP cannot determine the specific server (sub) layer entity that has
encountered defect conditions upon receiving a frame with ETH-AIS information. More importantly, it
cannot determine the associated subset of its peer MEPs for which it should suppress alarms because the
received ETH-AIS information does not contain that information. When a MEP receives a frame with
ETH-AIS information, it suppresses alarms for all peer MEPs whether there is still connectivity or not.
For a point-to-point ETH connection, however, a MEP has only one peer MEP. There is no ambiguity
regarding the peer MEP for which it should suppress alarms when it receives the ETH-AIS information.
Only a MEP, including a Server MEP, is configured to issue frames with ETH-AIS information. Once
the MEP detects a defect condition, it immediately starts transmitting periodic frames with ETH-AIS
information at a configured client maintenance level. We send the AIS frames at a configured MIP level