
fault, local stable, and remote stable using status bits. The OAM sublayer can also
send event and information to the link partner using OAM variable request and
response messages.
A very important function implemented in OAM is remote loopback, which
is shown in Figure 9.41. Figure 9.40 also indicates the loopback path in the
OAM sublayer. In the case of a network failure, the remote loopback function
allows an opera tor to quickly test the transmis sion link and narrow down the
fault location.
The MEF and ITU are now busy working on service provider OAM (SOAM)
functions for Ethernet services [16, 44], which we cannot cover here because of
space limits. ...