Using Rstp; Using Pvst; Using Mstp; Limitations Of Stp, Rstp, And Pvst - HP A5830 Configuration Manual

The device sends hello packets at the hello time interval to the neighboring devices to make sure that the
paths are fault-free.
Max age

The device uses the max age to determine whether a stored configuration BPDU has expired and discards
it if the max age is exceeded.

Using RSTP

RSTP achieves rapid network convergence by allowing a newly elected root port or designated port to
enter the forwarding state much faster under certain conditions than STP.
A newly elected RSTP root port rapidly enters the forwarding state if the old root port on the device has
stopped forwarding data and the upstream designated port has started forwarding data.
A newly elected RSTP designated port rapidly enters the forwarding state if it is an edge port (a port that
directly connects to a user terminal rather than to another network device or a shared LAN segment) or it
connects to a point-to-point link (to another device).
Edge ports directly enter the forwarding state. Connecting to a point-to-point link, a designated port
enters the forwarding state immediately after the device receives a handshake response from the directly
connected device.

Using PVST

PVST was introduced to improve link bandwidth usage in network environments where multiple VLANs
exist. Unlike STP and RSTP whose bridges in a LAN must forward their VLAN packets in the same
spanning tree, PVST allows each VLAN to build a separate spanning tree.
PVST uses the following BPDUs:
STP BPDUs—Sent by access ports according to the VLAN status, or by trunk ports and hybrid ports

according to the status of VLAN 1.
PVST BPDUs—Sent by trunk port and hybrid ports according to the status of permitted VLANs except

VLAN 1.

Using MSTP

Limitations of STP, RSTP, and PVST

STP does not support rapid state transition of ports. A newly elected port must wait twice the forward
delay time before it transits to the forwarding state, even if it connects to a point-to-point link or is an
edge port.
Although RSTP supports rapid network convergence, it has the same drawback as STP—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.
The number of PVST BPDUs generated grows with that of permitted VLANs on trunk ports. When the
status of a trunk port transitions, network devices can be overloaded to re-calculate a large number of
spanning trees.
53