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DES-7200 Configuration Guide Chapter 10 Redundancy Configuration for Management
Module
10-3
10.1.2 NSF Advantages and Limits
The advantages of NSF technology implementation in network service are:
Improving the network availability:
NSF technology maintains the information of data forwarding and user session
status in the process of device change.
Preventing the neighbour from detecting link flap:
The forwarding side does not reboot during the switchover, so the neighbour
can not detect the link status change from Down to Up.
Preventing routing flaps:
The forwarding side maintains to forward and communicate during the
switchover and the control side forms new forwarding list quickly without
apparent substitution between the new and oil forwarding list, thus preventing
routing flaps.
User sessions will not be lost:
User sessions built before the switchover will not be lost due to the
synchronization in real time.
The limits of using NSF technology in the switch are:
NSF works well on the premise that the software and hardware constitution of
the dual the management modules are consistent.
It should synchronizes the master and the slave management modules in batch
to make them consistent, before which is the window period when NSF can not
take effect.
Not all the functions related with forwarding are synchronized. The switch
function can be classified into the following types according to NSFsupporting
degree:
z High availability support function;
z Real time synchronization of status information between master and the
slave management module. For example, it synchronizes the control side
function directly related with L2 forwarding in real time.
z High availability compatibility function
z These features do not support high availability for the status datas are not
synchronized. However, when enabling high availability, these functions that
starts to run from initialization can still be used after switching.
z High availability incompatibility function