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 c entral office equip ment has been busied
out.

EPN Cabinet with Power Holdover

When power is interrupted to an EPN MCC for less than 15 seco nds, no service
effect results. If the interruption excee ds 15 seconds, only the c ontrol carrier is
kept up. Circuit p acks on other carriers are powe red down. Only calls and other
services maintained b y circuit pac ks on the control carrier are maintained . For
this reason, critical services and those that require a long time to resto re (for
example, Announcement circ uit packs) should be located on c ontrol 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 ag ainst AC-POWER.

External Alarm Leads

Each cabinet provid es two leads for one major and one min or alarm contact
closure that can be c onnected to external eq uipment. 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 equip ment
connected to these lead s and reported to INADS. These may be used to report
failures of UPSs or battery reserves powering the switc h. They are also
commonly used to monitor ad juncts such as AUDIX.
Protocols
This section describes the p rotocols handled by the system and the points where
these protocols chang e. Figure 1-9 is a pictorial g uide through data-
transmission state changes. Figure 1-9 illustrates the flow of data from DTE
equipment, like a terminal or host, throug h DCE equipment, like a modem or data
module, into a communica tions port on the system. The data flow is shown b y
solid lines. Below these lines are the protoc ols used at partic ular 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 informati on. These elements conform to
ISDN level-3 protocol. In the case of BRI, the elements are c reated by the
terminal or data module; for the PRI, the elements are created b y the system,
which inserts them into the D-channel a t 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 s ystem for
processing.