192
Figure 66 Inverse address resolution procedure of InARP
ATM OAM
OAM in the ITU-T I.610 recommendation (02/99) and Operation Administration and Maintenance in
LUCENT APC User Manual (03/99).
Whichever expansion is adopted, OAM provides a way of detecting faults, isolating faults, and
monitoring network performance without interrupting ongoing services. By inserting OAM cells,
which are constructed in the standard ATM cell format, in cell streams, you can obtain specific
information about the network.
OAM F5 loopback
The OAM F5 loopback function of ATM operates in the following workflow on a PVC:
Each side of the PVC sends OAM cells to its peer periodically. On receiving an OAM cell from the
sender, the receiver returns the OAM cell to the sender. If the sender receives the cell within the
specified period (which is the interval frequency of sending OAM cells), the PVC is normal. If the
sender fails to receive an OAM cell sent by itself, the PVC might be faulty. Then the sender continues
to send OAM cells for detection (the sending interval is retry-frequency). If the sender still does not
receive an OAM cell, the PVC is actually faulty.
Two methods are available for implementing the OAM F5 Loopback function: manual (OAMPing)
and auto (OAM Frequency). In the OAMPing method, send OAM cells manually; this method is
usually used for diagnosis. In the OAM Frequency method, you must configure an ATM interface to
send OAM cells regularly at a certain interval; this method is usually used for automatic link status
checking.
OAM continuity check
When enabled, the OAM Continuity Check (CC) function periodically sends OAM cells to check
whether a connection is idle or has failed.
OAM CC works on a PVC, where one side of the PVC sends OAM cells to its peer. The peer checks
the connection status based on these OAM cells.
Hardware compatibility with ATM
ATM interfaces are not available on the following routers:
• MSR1000.
• MSR30-11E.
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