Chapter 2 Module Description
Protection Features
2-2
255-700-585
PacketStar
®
PSAX 3-Port DS3/E3 ATM Protection Module User Guide
, Issue 1
Release 10.0.0
Protection Features
The 3-Port DS3/E3 ATM Protection module provides 1:1 protection on the
PSAX 1000 and N:1 protection on the PSAX 4500.
1:1 Protection Feature
The following sections describe how all aspects of the 1:1 Protection feature
work.
1:1 Traffic Protection
Modules
The 1-to-1 (1:1) Protection feature on the PSAX 1000 Multiservice Media
Gateway system provides traffic protection by configuring the system to use
the 1:1 Traffic Protection modules. These modules do not have external con-
nectors, but receive traffic from and transmit traffic to the network by physi-
cal connection at the PSAX 1000 chassis midplane to corresponding 3-Port
Line Interface modules (LIM3–1 modules). The 1:1 Traffic Protection mod-
ules are installed at the front of the chassis. The LIM3–1 modules, which are
installed at the rear of the chassis, receive incoming traffic and transmit out-
going traffic via the attached network cables on the external connectors on
the faceplates. The LIM3–1 modules are electrically connected to the protec-
tion module for a protection group via the midplane.
Protection Group
The 1:1 Protection feature supports the configuration of one protection group
for the PSAX 1000 system that contains one working module and one pro-
tection module of the same type, and one LIM3–1 module for the working
module. The working module is installed in slot
4
and the protection module
is installed in slot
15
. A LIM3–1 module is installed directly behind the work-
ing module.
In the 1:1 scheme, one working module in a protection group is associated
with one protection module. Under normal conditions, the working module
in a protection group is in Active mode, exchanging traffic, and the protec-
tion module is in Standby mode.
The 1:1 Traffic Protection modules can also be used in a nonprotected config-
uration in which one of these modules can be installed in slot
4
with a corre-
sponding LIM3–1 module installed directly behind it.
Working Module
Monitoring
Traffic is switched from a working module to its associated protection module
under the following conditions:
•
Working module failure
•
Removal of the working module from the chassis
•
Manual switchover initiated by the user
•
Nonservice affecting upgrades
The protection module monitors the operation of the working module. Inter-
Slot Communication (ISC) cells are exchanged between the working and
protection module. If the protection module detects eight consecutive miss-
