The status reported by the service and service acknowledge messages for B-channels and
ISL channels are:
• in-service
• maintenance
• out-of-service
Near-end and far-end sub-categories are defined for each maintenance status. See Table 40:
Maintenance message and status combinations on page
101 for possible combinations of
near-end and far-end statuses, and the channel capability for each status. When the near-end
and far-end status does not match, the more severe maintenance status takes effect over the
less severe maintenance status.
Table 40: Maintenance message and status combinations
Near-end status Far-end status B or ISL channel capability
In-service In-service Incoming and outgoing call allowed
In-service Maintenance Incoming calls allowed only
In-service Out-of-service Not allowed to use
Maintenance N/A Not allowed to use
Out-of-service N/A Not allowed to use
Note:
Enabling/Disabling of Service Messages must be coordinated between the two ends.
Enabling Service Messages at one end and not the other results in B-channels being placed
out-of-service.
Message functions
Service messages are used to monitor the following:
•
D-channel establishment
• D-channel sanity polling
• B-channel or ISL channel status change
• Channel status audit
D-channel establishment
When the D-channel establishes, the B-channel status is supported by sending service
messages for each B-channel controlled by a D-channel. This messaging allows the far end
to synchronize its channel states. The service messages are sent when the system brings up
the D-channel automatically or an administrator brings up the D-channel manually by using
LD 96.
Monitor DTI/PRI operation
ISDN Primary Rate Interface Maintenance November 2011 101
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