ZyXEL Communications Multi-service Access Platform MSAP2000 - Manual (Page 101)

6. System Design
MSAP2000 Technical Manual V3.0 6-4
6.3. Redundancy and Protection Design
Overview
MSAP2000 universal shelf allows most of the modules to be
hot-swappable without interruption or and influence to the existing
traffic and services, for the convenience of maintenance and system
upgrade.
Power Protection
Design
Both CoPSM and RtPSM provide redundancy and load-sharing, as
well as real-time monitoring and alarm function. These two modules
will provide main power conversion under normal operating conditions.
And in any event they are designed to achieve high reliability.
MPM 1:1 Protection
Design
MPM uses 1:1 protection, so that when an active MPM fails, the
system can automatically switch to the standby MPM, to ensure
operation stability. The switch-over between the active and standby
MPM modules will cause any service interruption.
ELM/EPM 1:1
independent
protection Design
The Main Shelf and Extension Shelf are linked by a star connection
layout, instead of a cascade-tiered connection layout. This is to
prevent one extension shelf connection failure from disrupting the
connection status of other extension shelves. When expansion is
used, slots at main shelf should be reserved for later installation.
Modules on new expansion will be added to network database
automatically once the link between ELM & EPM is established.
Channel assignment can then be added without interfering the existing
traffic and service. To ensure transmission connection stability
between the main shelf and extension shelf, both ELM and EPM
provide 1:1 protection. When an active ELM or EPM fails, the System
will automatically switch to the Standby ELM or EPM Link, to ensure
un-interrupted connection.
OIM/SM1/SM4 1:1
Protection
Design
The OIM/SM1/SM4 trunk interface provides 1:1 card protection. The
switching time is less than 50ms, and will not interrupt services.
OIM/SM1/SM4 Ring
Protection
Design
The OIM/SM1/SM4 optic trunk interface supports ring protection. The
service interruption time for E1 leased line subscribers is <50ms; and
ongoing voice services will not be interrupted. OIM/SM1/SM4 can
support protection switching, based on its pre-set threshold switch
value (such as BER). Besides pre-set protection switching, Users
can also manually conduct protection switching via the NMS and LCT
(Local Craft Terminal) interface. In the event of an OIM/SM1/SM4
protection switch failure, the System will generate an alarm.
QE1M N+1
protection design
When E1 is used as trunk in point-to-point topology, additional E1 ports
can be used as protection. The traffic will be routed automatically to
the active E1 when other E1s go down.
Service modules
N+1 protection
design
For analog voice module, the protection is realized at COT network
side. Total subscribers available are determined by switch operator
and therefore form N+1 protection where N equals to the total number
of the subscriber module, in this case, all FXS/E&M in the system.
For V5 PSTN/ISDN service, the protection is also achieved at COT
network side, the V5 El links. Concentration ratio is decided by the total
number of E1 provided by the LE interface and the total subscribers
that interface intend to provide. Thus the N+1 protection forms as N
equals to the number of E1 links for each interface. When one of the