IEEE 802.1ag Standards

Support for IEEE 802.1ag Ethernet CFM (Connectivity Fault Management) Protocols, which provide end-to-end Ethernet management, includes:

1) path discovery
2) link monitoring
3) remote fault detection and notification
4) remote loopback

Salira CFM comprises three protocols to detect, isolate, and notify Ethernet network connectivity fault; they are:

1) continuity check --

these are "hello" messages issued periodically by maintenance endpoints to:

a) discover other maintenance endpoints and intermediate points within a maintenance domain
b) to detect loss of service connectivity among maintenance endpoints
c) to detect misconfiguration, such as VLAN ID mismatch, of maintenance endpoints
d) to detect bogus maintenance endpoints that intrude into the maintenance domain

2) link trace (aka L2 trace) --

these are transmitted by maintenance endpoints on the request of the administrator
to track the path hop-by-hop to any maintenance point (endpoint or intermediate point)
within a maintenance domain. 
This feature is similar in concept to UDP traceroute.

3) loopback (aka L2 ping) --

these are transmitted by maintenance endpoints on the request of the administrator
to verify reachability to any maintenance point (endpoint or intermediate point)
within a maintenance domain. 
This feature is similar in concept to ICMP echo (ping).

By deploying Salira CFM in provider Ethernet network, the network administrator can easily :

1) detect which customer service is down via proactive continuity check and fault report
2) verify the loss of service connectivity by using loopback (or l2ping) tool
3) localize the service connection faulure by using link trace (or l2trace) tool

Figure 1: Hierarchical Maintenace Domains & Maintenace points