Medium Access Control (MAC) and Physical Layer (PHY) - CISE

4-June-07 P1901_PRO_016_r0
STP packets will be transmitted through the corresponding unicast ports.
IEEE 802.1D (Spanning Tree Protocol)
The 802.1D recommendation describes the Spanning Tree algorithm and protocol. In this document, the calculation
of the tree elements and the messages exchanged between bridges for this purpose are exposed. This specification is
fully compliant with this standard.
The implementation of IEEE 802.1D is a must for network compatibility.
For specific information on message types and their fields and the algorithm to handle them, refer to IEEE Std 802.1
and IEEE Std 802.1D (Spanning Tree).
Ports can be Ethernet or BPL. Every new BPL connection is added to the bridge as a new port. Ports can be deleted
when the BPL connection is lost for some physical reason. Some ports, such as Ethernet ports, are always present.
Each port carries out the STP.
Default timers and field values
The IEEE recommendation is relatively flexible in some aspects, such as default timer values and other message
fields, so that they can be tuned for different network sizes and Medium Access technologies. The values adopted
by this specification for these parameters are:
hello: time between each BPDU that is sent on a port.
Default: 2 seconds
Range: [1, 10] seconds
forward delay: time spent in the listening and learning states.
Default: 15 seconds
Range: [4, 30] seconds
max age: maximum length of time a bridge port saves its configuration.
Default: 20 seconds
Submission page 277 UPA-OPERA