Juniper JUNOSE 11.1.X - LINK LAYER CONFIGURATION 4-7-2010, Configuration Manual

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Continuity Verification
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:
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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 17 for
more details.)
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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:
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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.
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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.
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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 .
Operations, Administration, and Management of ATM Interfaces
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Chapter 1: Configuring ATM