3com S7906E Manuel De Montage

 

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STP does not support rapid state transition of ports. A newly elected root port or designated port must 
wait twice the forward delay time before transiting to the forwarding state, even if it is a port on a 
point-to-point link or an edge port, which directly connects to a user terminal rather than to another 
device or a shared LAN segment. 

Although RSTP supports rapid network convergence, it has the same drawback as STP does: All 
bridges within a LAN share the same spanning tree, so redundant links cannot be blocked based on 
VLAN, and the packets of all VLANs are forwarded along the same spanning tree. 

Developed based on IEEE 802.1s, MSTP overcomes the shortcomings of STP and RSTP. In addition to 
the support for rapid network convergence, it allows data flows of different VLANs to be forwarded along 
separate paths, thus providing a better load sharing mechanism for redundant links. For description 
about VLANs, refer to VLAN Configuration in the Access Volume. 

MSTP features the following: 

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MSTP supports mapping VLANs to spanning tree instances by means of a VLAN-to-instance 
mapping table. MSTP can reduce communication overheads and resource usage by mapping 
multiple VLANs to one instance. 

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MSTP divides a switched network into multiple regions, each containing multiple spanning trees 
that are independent of one another. 

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MSTP prunes a loop network into a loop-free tree, thus avoiding proliferation and endless cycling of 
packets in a loop network. In addition, it provides multiple redundant paths for data forwarding, thus 
supporting load balancing of VLAN data.  

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MSTP is compatible with STP and RSTP.