DEFINITY Enterprise Communications Server Release 7
Maintenance for R7r
555-230-126
Issue 4
June 1999
Maintenance Architecture
1-28Protocols
1
power is restored, taking up to 15 minutes, depending on the size of the system.
Human intervention may be required if central office equipment has been busied
out.
EPN Cabinet with Power Holdover
When power is interrupted to an EPN MCC for less than 15 seconds, no service
effect results. If the interruption exceeds 15 seconds, only the control carrier is
kept up. Circuit packs on other carriers are powered down. Only calls and other
services maintained by circuit packs on the control carrier are maintained. For
this reason, critical services and those that require a long time to restore (for
example, Announcement circuit packs) should be located on control carriers. All
service to Port Networks connected to a Switch Node in the EPN is lost. When
power is restored, all affected EPNs are reset by system software (see
‘‘EXP-PN
(Expansion Port Network)’’ in
Chapter 9, ‘‘Maintenance Object Repair
Procedures’’). As with the PPN, a warning alarm is raised against AC-POWER.
External Alarm Leads
Each cabinet provides two leads for one major and one minor alarm contact
closure that can be connected to external equipment. These are located on the
SYSAM and Maintenance circuit packs. If the switch is under warranty or a
maintenance agreement, EXT-DEV alarms are generated by the equipment
connected to these leads and reported to INADS. These may be used to report
failures of UPSs or battery reserves powering the switch. They are also
commonly used to monitor adjuncts such as AUDIX.
Protocols
This section describes the protocols handled by the system and the points where
these protocols change.
Figure 1-9
is a pictorial guide through data-
transmission state changes.
Figure 1-9
illustrates the flow of data from DTE
equipment, like a terminal or host, through DCE equipment, like a modem or data
module, into a communications port on the system. The data flow is shown by
solid lines. Below these lines are the protocols used at particular points in the
data stream.
Not shown in the Figure 1-9
is the treatment of D-channels in ISDN-PRI and
ISDN-BRI transmissions. PRI and BRI D-channels transport information elements
that contain call-signaling and caller information. These elements conform to
ISDN level-3 protocol. In the case of BRI, the elements are created by the
terminal or data module; for the PRI, the elements are created by the system,
which inserts them into the D-channel at the DS1 port.
For ISDN transmissions, therefore, BRI terminals and data modules, and DS1
ports insert, interpret, and strip both layer-2 DCE information and layer-3
elements. Also, the DS1 port passes layer-3 elements to the system for
processing.
