Difference Between RSTP and PVST

The Rapid Spanning Tree Protocol (RSTP) and the Per-VLAN Spanning Tree Protocol (PVST) are protocols used in Ethernet networks to prevent loops and provide network connection redundancy.

RSTP is a Spanning Tree Protocol (STP) evolution that is designed to provide faster convergence times in response to changes in network topology. PVST is a Cisco proprietary protocol that creates a separate spanning tree for each VLAN using STP.

Read this article to find out more about RSTP and PVST and how they are different from each other.

What is RSTP?

Rapid Spanning Tree Protocol (RSTP) is an evolution of Spanning Tree Protocol (STP) that allows for faster convergence times in response to changes in network topology. RSTP accomplishes this by using a more efficient algorithm for calculating network topology and providing faster port transition times.

RSTP works by selecting a root bridge, which is the central point of the spanning tree. RSTP calculates the shortest path from the root bridge to each network segment, known as a port. RSTP then forwards or blocks each port based on whether it is on the shortest path to the root bridge.

In many ways, RSTP performs better than STP in terms of convergence times. First, it calculates the network topology using a faster algorithm. This algorithm is known as the Rapid Convergence Algorithm (RCA), and it detects changes in the network topology and calculates the new spanning tree without waiting for the forwarding delay timer to expire.

Second, RSTP allows for faster port transitions. When a port goes from blocking to forwarding, it accomplishes this without waiting for the forwarding delay time to expire. This is known as edge port detection, and it helps minimise network downtime.

Third, by providing the concept of a backup port, RSTP allows for faster convergence times. If a connection fails, the backup port can take over instantly without having to wait for the spanning tree to recalculate.

RSTP also has a feature called Port Roles that allows administrators to prioritise specific ports and customise how RSTP selects the best path to the root bridge. A network administrator, for example, can classify a port as a backup port or a designated port based on its priority.

What is PVST?

Per-VLAN Spanning Tree (PVST) is a Cisco proprietary protocol that creates a separate spanning tree for each VLAN using the Spanning Tree protocol (STP). This allows load balancing across many VLANs while also providing faster convergence times than the traditional STP protocol.

PVST works by creating a separate spanning tree for each VLAN on the network. This allows administrators to customise the spanning tree to the individual needs of each VLAN. Each VLAN has its own root bridge, and the path to it is calculated separately for each VLAN.

Rapid PVST (RPVST) is a faster version of PVST that is included with PVST. RPVST calculates network topology using a more efficient algorithm, resulting in faster convergence times in response to changes in network topology.

PVST uses numerous approaches to achieve faster convergence times than STP. First, it calculates the network topology using a faster algorithm. Second, it provides faster port transition times through the use of edge port detection, which allows a port to change from blocking to forwarding without waiting for the forwarding delay timer to expire.

PVST may also balance loads across multiple VLANs. Instead of a single spanning tree for the entire network, multiple spanning trees, one for each VLAN, are used. This allows traffic to be dispersed across various paths, which helps in network congestion prevention.

PVST includes a number of features that allow network administrators to customise the spanning tree for each VLAN. Administrators, for example, can set the priority of the root bridge for each VLAN, designate ports as root or designated ports, and set the path cost for each port.

Difference between RSTP and PVST

The following table highlights the major differences between RSTP and PVST −

Characteristics	RSTP	PVST
Protocol	Standard Protocol	Cisco Proprietary Protocol
Algorithm	Rapid Convergence Algorithm (RCA)	STP
Convergence Time	Faster than STP	Faster than STP
Port Transition Time	Faster than STP	Faster than STP
Backup Port	Supported	Supported
Load Balancing	Not Supported	Supported
VLAN Support	It supports all VLANs.	Separate Spanning Tree for Each VLAN
Port Roles	Supported	Supported
Widely Supported	Yes	It is limited to Cisco Networks.
Calculation of Network Topology	More Efficient	Separate Spanning Tree for Each VLAN
Full Form	Rapid Spanning Tree Protocol.	Per-VLAN Spanning Tree Protocol

Conclusion

In conclusion, while both RSTP and PVST are protocols used in Ethernet networks to prevent loops and maintain network redundancy, they have significant differences. RSTP is a standard protocol that calculates network topology more efficiently and delivers faster port transition times, resulting in faster convergence times.

PVST, on the other hand, is a proprietary Cisco protocol that produces a separate spanning tree for each VLAN, allowing for load balancing across several VLANs and faster convergence times than STP. As a result, the decision between RSTP and PVST may depend on factors such as network size, complexity, and equipment used.