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JunosE 11.2.x Link Layer Configuration Guide
Continuity Verification
16
The OAM VC status field of "show atm vc atm" on page 90 shows whether the circuit is
in RDI state.
CC cells provide continual monitoring of a connection on a segment or end-to-end basis.
To verify the integrity of the link, you can set up a VP or VC to regularly send or receive
CC cells at either the segment level or at the end-to-end level.
The CC cell source generates the CC cells, and the sink receives and processes the cells.
You can set up a VP or VC as the source, the sink, or both the source and the sink. If you
enable a VP or VC as a CC cell source, it generates CC cells. The VP or VC counts CC cells
whether or not CC cell flow is enabled. You can enable CC cells only on data circuits, not
on control circuits, such as ILMI or signaling circuits.
Activation and Deactivation Cells
To enable and disable CC cell flows, ATM OAM uses activation and deactivation cells:
To enable a CC cell flow, the router sends activation OAM cells to the peer. The peer
replies with a confirmation or denial. If the CC sink point is not activated, all received
CC cells are dropped. (See "Activating CC Cell Flow" on page 16 for more details.)
To disable a CC cell flow, the router sends deactivation OAM cells to the peer. The peer
replies with a confirmation or denial.
Activating CC Cell Flow
When the router sends a CC activation cell to the peer, one of the following occurs:
If the router receives a positive response (Activation Confirmed), the VC or VP goes to
CC active state, and CC is enabled on the VC or VP.
If the router receives a negative response (Activation Req. Denied), the VC or VP goes
to CC failed state, and CC is not enabled on the VC or VP.
If the router does not receive a response within 5 seconds, it sends another activation
cell. This process is repeated three times. If the router does not receive a response, it
stops the activation process.
If the VC or VP is the source point, CC cell generation starts as soon as the router sends
the activation request to the peer. CC cell generation stops if the CC fails, when the
maximum number of retries is reached, or when the deactivation process is complete.
Deactivating CC Cell Flow
The process of sending a deactivation request is the same as for activation cells except
that deactivation cells are sent instead.
Also, the atm oam flush command causes the router to send a deactivation request to
the peer and suspend all CC operations. Therefore, we recommend that you disable CC
cell generation and transmission on all VCs before issuing atm oam flush.
Copyright © 2010, Juniper Networks, Inc.
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