Spanning Tree Protocol Entity

The Spanning Tree Protocol Entity is described in 7.10, Clause 8, and Clause 17. The objects that comprise this managed resource are as follows:

a) The Protocol Entity itself, and b) The Ports under its control.

14.8.1 The Protocol Entity

The Protocol Entity object models the operations that can be performed upon, or inquire about, the operation of the Spanning Tree Protocol. There is a single Protocol Entity per Bridge; it can, therefore, be identified as a single fixed component of the Protocol Entity resource.

The management operations that can be performed on the Protocol Entity are Read Spanning Tree Protocol Parameters and Set Spanning Tree Protocol Parameters.

14.8.1.1 Read Spanning Tree Protocol parameters 14.8.1.1.1 Purpose

To obtain information regarding the Bridge’s Spanning Tree Protocol Entity.

14.8.1.1.2 Inputs

None.

14.8.1.1.3 Outputs

a) Bridge Identifier—as defined in 17.18.3.

b) Time Since Topology Change—the count in seconds of the time since the tcWhile timer (17.17.8) for any Port was non-zero.

c) Topology Change Count—the count of times that there has been at least one non-zero tcWhile timer (17.17.8).

d) Topology Change— asserted if the tcWhile timer (17.17.8) for any Port is non-zero.

e) Designated Root (17.18.6).

f) Root Path Cost (17.18.6).

g) Root Port (17.18.6).

h) Max Age (17.18.7).

i) Hello Time (17.13.6).

j) Forward Delay (17.13.5).

k) Bridge Max Age (17.18.4).

l) Bridge Hello Time (17.18.4).

m) Bridge Forward Delay (17.18.4).

n) TxHoldCount (17.13.12).

o) forceVersion (17.13.4).

14.8.1.2 Set Spanning Tree Protocol parameters 14.8.1.2.1 Purpose

To modify parameters in the Bridge’s Spanning Tree Protocol Entity in order to force a configuration of the spanning tree and/or tune the reconfiguration time to suit a specific topology, this operation causes these values to be set for all Ports of the Bridge.

14.8.1.2.2 Inputs

a) Bridge Max Age—the new value (17.18.4).

b) Bridge Hello Time—the new value (17.18.4).

c) Bridge Forward Delay—the new value (17.18.4).

d) Bridge Priority—the new value of the priority part of the Bridge Identifier (17.18.3).

e) forceVersion—the new value of the Force Protocol Version parameter (17.13.4).

f) TxHoldCount— the new value of TxHoldCount (17.13.12).

14.8.1.2.3 Outputs

a) Operation status. This takes one of the following values:

1) Operation rejected due to invalid Bridge Priority value (14.1); or 2) Operation accepted.

14.8.1.2.4 Procedure

The input parameter values are checked for compliance with 17.14. If they do not comply, or the value of any of Bridge Max Age, Bridge Forward Delay, or Bridge Hello Time is outside the range specified in Table 17-1, no action shall be taken for any of the supplied parameters.

Otherwise:

a) The Bridge’s Bridge Max Age, Bridge Hello Time, and Bridge Forward Delay parameters are set to the supplied values.

b) The priority component of the Bridge Identifier (17.18.3) is updated using the supplied value as specified in 17.13.

14.8.2 Bridge Port

A Bridge Port object models the operations related to an individual Bridge Port in relation to the operation of the Rapid Spanning Tree Protocol. There are a fixed set of Bridge Ports per Bridge; each can, therefore, be identified by a permanently allocated Port Number, as a fixed component of the Protocol Entity resource.

The management operations that can be performed on a Bridge Port are Read Port Parameters, Force Port State, Set Port Parameters, and Force BPDU Migration Check.

14.8.2.1 Read Port Parameters 14.8.2.1.1 Purpose

To obtain information regarding a specific Port within the Bridge’s Spanning Tree Protocol Entity.

14.8.2.1.2 Inputs

a) Port Number—the number of the Bridge Port.

14.8.2.1.3 Outputs

a) Uptime—count in seconds of the time elapsed since the Port was last reset or initialized.

b) State—the current state of the Port (i.e., Discarding, Forwarding, or Blocking) (7.4).

c) Port Identifier—the unique Port identifier comprising two parts, the Port Number and the Port Priority field (17.19.19).

d) Path Cost (17.13.11).

e) Designated Root (17.19.21).

f) Designated Cost (17.19.21).

g) Designated Bridge (17.19.21).

h) Designated Port (17.19.21).

i) Topology Change Acknowledge (17.19.41).

j) adminEdgePort (17.13.1). Present in implementations that support the identification of edge ports.

k) operEdgePort (17.19.17). Present in implementations that support the identification of edge ports.

l) autoEdgePort (17.13.3). Optional and provided only by RSTP Bridges that support the automatic identification of edge ports.

m) MAC Enabled—the current state of the MAC Enabled parameter (6.4.2). Present if the implementation supports the MAC Enabled parameter.

n) MAC Operational—the current state of the MAC Operational parameter (6.4.2). Present if the implementation supports the MAC Operational parameter.

o) adminPointToPointMAC—the current state of the adminPointToPointMAC parameter (6.4.3).

Present if the implementation supports the adminPointToPointMAC parameter.

p) operPointToPointMAC—the current state of the operPointToPointMAC parameter (6.4.3). Present if the implementation supports the operPointToPointMAC parameter.

14.8.2.2 Force port state 14.8.2.2.1 Purpose

To set the Administrative Bridge Port state (see 7.4) for the specified Port to Disabled or Enabled.

14.8.2.2.2 Inputs

a) Port Number—the number of the Bridge Port.

b) State—either Disabled or Enabled.

14.8.2.2.3 Outputs

None.

14.8.2.2.4 Procedure

The effect of changing this parameter is defined by 17.19.18 and the state machines specified in Clause 17.

14.8.2.3 Set Port Parameters 14.8.2.3.1 Purpose

To modify parameters for a Port in the Bridge’s Spanning Tree Protocol Entity in order to force a configuration of the spanning tree.

14.8.2.3.2 Inputs

a) Port Number—the number of the Bridge Port.

b) Path Cost—the new value (17.13.11).

c) Port Priority—the new value of the priority field for the Port Identifier (17.19.21).

d) adminEdgePort—the new value of the adminEdgePort parameter (17.13.1). Present in implementations that support the identification of edge ports.

e) autoEdgePort — the new value of the autoEdgePort parameter (17.13.3). Optional and provided only by RSTP Bridges that support the automatic identification of edge ports.

f) MAC Enabled—the new value of the MAC Enabled parameter (6.4.2). May be present if the implementation supports the MAC Enabled parameter.

g) adminPointToPointMAC—the new value of the adminPointToPointMAC parameter (6.4.3). May be present if the implementation supports the adminPointToPointMAC parameter.

14.8.2.3.3 Outputs

a) Operation status. This takes one of the following values:

1) Operation rejected due to invalid Port Priority value (14.3); or 2) Operation accepted.

14.8.2.3.4 Procedure

The Path Cost (17.13.11) and Port Priority (17.19.21) parameters for the Port are updated using the supplied values. The reselect parameter for the Port (17.19.34) is set TRUE, and the selected parameter for the Port (17.19.36) is set FALSE.

14.8.2.4 Force BPDU Migration Check 14.8.2.4.1 Purpose

To force the specified Port to transmit RST BPDUs (see 17.24).

14.8.2.4.2 Inputs

a) Port Number—the number of the Bridge Port.

14.8.2.4.3 Outputs

None.

14.8.2.4.4 Procedure

The mcheck variable (17.19.13) for the specified Port is set to the value TRUE if the value of the forceVersion variable (17.13.4) is greater than or equal to 2.