255-700-585
2-5
PacketStar
®
PSAX 3-Port DS3/E3 ATM Protection Module User Guide
, Issue 1
Release 10.0.0
Chapter 2 Module Description
Protection Features
When the user executes the switchover command, the PSAX system
instructs the LIM
nn
module to switch the traffic from the protection mod-
ule running in Active mode to the working module. The working module
is then placed into Active mode and the protection module is placed into
Standby mode.
•
Replacement working module
When the user inserts the new replacement module into the chassis, the
PSAX system recognizes it as an unconfigured module. The user then exe-
cutes the switchover command, and the PSAX system downloads the mod-
ule and connection configurations from the protection module to the new
working module. After this download is finished, the system instructs the
LIM
nn
module to switch the traffic from the protection module running in
Active mode to the working module. The working module is then placed
into Active mode and the protection module is placed into Standby mode.
The connection downtime during this manual switchover in the previous
scenarios is only the amount of time needed to switch the LIM
nn
module.
N:1 Protection Feature
The following sections describe how all aspects of the N:1 Protection feature
work.
N:1 Traffic Protection
Modules
The N-to-1 (N:1) Protection feature on the PSAX 4500 Multiservice Media
Gateway system provides traffic protection by configuring the system to use
the N: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 4500 chassis midplane to corresponding 3-Port
Line Interface modules (LIM3–4 modules). The N:1 Traffic Protection mod-
ules are installed at the front of the chassis. The LIM3–4 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 LIM3–4 modules are electrically connected to the protec-
tion module for a protection group via the midplane.
Protection Groups
The N:1 Protection feature supports the configuration of one or two protec-
tion groups for the PSAX 4500 system, with each group containing either
one-to-six or one-to-four working modules of the same type, one LIM3–4
module for each working module, and one protection module of the same
type for each group. The protection groups are set up as follows.
•
For group 1, up to six working modules are installed in slots
3
,
4
,
5
,
6
,
7
,
and
8
, and the protection module is installed in slot
15
. A LIM3–4 module
is installed directly behind each working module.
•
For group 2, up to four working modules are installed in slots
9
,
10
,
11
, and
12
, and the protection module is installed in slot
13
. A LIM3–4 module is
installed directly behind each working module.
Two types of protection schemes are supported for each protection group: N:1
and 1:1. In the N:1 scheme, one to six working modules are associated with
one protection module in group 1, and one to four working modules are
