Figure 17-7
17.1.1.7 Quick Convergence of RSTP
We now introduce the special function of RSTP, which enables the ―quick‖ forwarding of the
port.
The STP protocol will carry out the forwarding after 30s since the port role is selected.
Furthermore, the Root port and Designated port of each bridge will carry out the forwarding
again after 30s, so it will take about 50s to stabilize the tree-type structure of the whole
network topology.
The forwarding of the RSTP port is different. As is shown in Figure 17-8, the Switch A will
send the ―Proposa‖l packet dedicated for the RSTP, the Switch B detects that the priority of
Switch A is higher than itself, takes the Switch A as the root bridge and carries out the
forwarding immediately after the port that receives the packet is the Root Port, and then
sends the ―Agree‖ packet to Switch A from Root Port. The Designated Port of Switch A is
agreed and carries out the forwarding. Then, the Designated Port of Switch B sends the
proposal message to deploy the spanning tree in turn. In theory, the RSTP can immediately
restore the tree-type network structure to implement the quick convergence when the
network topology changes.
To Next Page
Loading...
