Nonstop Forwarding - Alcatel-Lucent 7450 Basic System Configuration Manual

However, in a centralized architecture, packet processing and forwarding is performed in a
central shared route processor and the individual line cards are relatively simple. The cards
rely solely on the route processor for routing and forwarding intelligence and, should the
centralized route processor fail, there is greater impact to the system overall, as all routing
and packet forwarding will stop.
In a distributed system, the packet forwarding functionality is situated on each line card.
Distributing the forwarding engines off the central route processor and positioning one on
each line card lowers the impact of route processor failure as the line cards can continue to
forward traffic during an outage.
The distributed system is better suited to enable the convergence of business critical services
such as real-time voice (VoIP), Video, and VPN applications over IP networks with superior
performance and scalability. The centralized architecture can be prone to performance
bottleneck issues and limits service offerings through poor scalability which may lead to
customer and service SLA violations.
Service Redundancy
All service-related statistics are kept during a switchover. Services, SDPs, and SAPs will
remain up with a minimum loss of forwarded traffic during a CPM switchover.
Accounting Configuration Redundancy
When there is a switchover and the standby CPM becomes active, the accounting servers will
be checked and if they are administratively up and capable of coming online (media present,
etc.), the standby will be brought online and new accounting files will be created at that point.
Users must manually copy the accounting records from the failed CPM.

Nonstop Forwarding

In a control plane failure or a forced switchover event, the router continues to forward packets
using the existing stale forwarding information. Nonstop forwarding requires clean control
plane and data plane separation. Usually the forwarding information is distributed to the
IOMs, XCMs and XMAs.
Basic System Configuration Guide
System Management
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