KBC Networks ESML6-P3 - Manual (Page 26)

Ethernet Switch User Manual
Manual_web_mgt_sw-ESML6-P3-Rev 1107
Copyright © KBC Networks Ltd. 2011 Page 25 of 51 www.kbcnetworks.com
Note:
The bridge ID is made up from the device’s bridge priority and MAC address, RSTP uses
these to determine the root bridge and root port. The lower the port priority number, the
higher its actual priority, the device with the lowest bridge ID will be chosen as the root
bridge. The bridge priority is set as the lowest but can be forced to be the root bridge. In
the case of the same priorities, the one with the lowest MAC address is the root bridge.
The Forward Delay Time, Max Age Time and Hello Time must follow these rules:
2 x (Bridge_Forward_Delay – 1.0 seconds) >= Bridge_Max_Age Bridge_Max_Age >= 2
x (Bridge_Hello_Time + 1.0 seconds).
The port path cost is the path expenses of the port link, and is used to calculate the
shortest path, which depends on link bandwidth. The greater the bandwidth, the lower
the link cost. The forwarding path from the current device to root port can be changed by
changing port link cost.
The port priority and port number make up the port ID, which is used for the root port
selection calculation. The smaller the port ID is, the higher the priority it has.
3.1.3.10 RSTP Transparent Transmission
RSTP is a redundant protection protocol and is the IEEE standard, it is not compatible
with the DT-Ring protocol which is available on the ESML6-P3 switch. If an RSTP network
is to be connected to one configured to use DT-Ring then RSTP Transparent Transmission
must be enabled.
RSTP transparent transmission is the process by which the switch forwards the received
RSTP frames to the port set in transparent mode. In an RSTP network the switch is
considered as transparent link.
The benefit of using the RSTP transparent transmission is that the switch can use its own
redundancy protocol which ensures the link reconfiguration time meets industrial
requirements.
In an RSTP domain the switches can be set to use the RSTP protocol and in a DT-Ring
domain they can be set to use the DT-Ring protocol; The RSTP is enabled in the ring port
and the RSTP transparent transmission is set in the switch port connected to the RSTP
domain.
Choose on each port whether RSTP transparent transmission should be enabled or
disabled. Select <Apply> to confirm these choices.
Example:
In the example below switches S1 & S2 are in the RSTP domain and switches A, B, C & D
are in the DT-Ring domain. RSTP transparent transmission is set on the switch ports of A
and C that are connected to the RSTP domain.