VBST, a Huawei spanning tree protocol, constructs a spanning tree in each VLAN so that traffic from different VLANs is forwarded through different spanning trees. VBST is equivalent to STP or RSTP running in each VLAN. Spanning trees in different VLANs are independent of each other.
Currently, there are three standard spanning tree protocols: Spanning Tree Protocol (STP), Rapid Spanning Tree Protocol (RSTP), and Multiple Spanning Tree Protocol (MSTP). STP and RSTP cannot implement VLAN-based load balancing, because all the VLANs on a LAN share a spanning tree and packets in all VLANs are forwarded along this spanning tree. In addition, the blocked link does not carry any traffic, which wastes bandwidth and may cause a failure to forward packets from some VLANs. In real-world situations, MSTP is preferred because it is compatible with STP and RSTP, ensures fast convergence, and provides multiple paths to load balance traffic.
On enterprise networks, enterprise users need functions that are easy to use and maintain, whereas the configuration of MSTP multi-instance and multi-process is complex and has high requirements for engineers' skills.
To address this issue, Huawei develops VBST. VBST constructs a spanning tree in each VLAN so that traffic from different VLANs is load balanced along different spanning trees. In addition, VBST is easy to configure and maintain.
Table 1 lists the comparisons between VBST and STP/RSTP/MSTP.
Spanning Tree Protocol |
Similarity |
Difference |
|||
|---|---|---|---|---|---|
Convergence Speed |
Traffic Forwarding |
Usage Scenario |
Complexity |
||
VBST |
Forms a loop-free tree topology to prevent broadcast storms and implement link backup. |
RSTP/MSTP/VBST provides faster convergence than STP. |
A spanning tree is formed in each VLAN, so that traffic from different VLANs is forwarded through different spanning trees that are independent of each other. |
|
Medium |
MSTP |
Provides mappings between MSTIs and VLANs so that traffic from different VLANs is forwarded through different spanning trees that are independent of each other. |
Service traffic needs to be differentiated and load balanced. |
High |
||
RSTP |
Maps all VLANs to one spanning tree, so traffic from all VLANs is forwarded through the same spanning tree. |
Service traffic does not need to be differentiated. |
Low |
||
STP |
Slowest |
Low |
|||