User's Manual

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Figure 1.3 Uplink Fast
Note:
The Uplink Fast characteristic adjusts to the slowly convergent SSTP and PVST. In RSTP and
MSTP mode, new root port can rapidly enter the Forwarding state without the Uplink Fast
function.
37.1.5 Backbone Fast
The Backbone Fast characteristic is a supplement of the Uplink Fast technology. The Uplink Fast technology
makes the redundancy line rapidly work in case the direct connection to the designated switch is disconnected,
while the Backbone Fast technology detects the indirect-link network blackout in the upper-layer network and
boosts the change of the port state.
In figure 1.3, Connection L2 between switch C and switch A is called as the direct link between switch C and
root switch A. If the connection is disconnected, the Uplink Fast function can solve the problem. Connection
L1 between devices A and B is called as the indirect link of device C. The disconnected indirect link is called
as indirect failure, which is handled by the Backbone Fast function.
The working principle of the Backbone Fast function is shown in Figure 1.4.