Ring topology

4th of January 2018
To ensure the protection of communication channels from single failure, they must be reserved. Reservation inevitably leads to the emergence of ring network sections - closed routes. The Ethernet standard provides only a tree topology and does not allow ring topologies, as this leads to looping of packets.
Spanning Tree Protocol (STP, IEEE 802.1d) support is implemented in PSW-2G4F switches, what allows creating ring routes in Ethernet networks. Constantly analyzing the network configuration, STP automatically builds a tree topology, transferring redundant communication lines to the reserve. In case of integrity violation of the network constructed in this way (for example, a break in the optics), STP in a few seconds includes the necessary backup lines, restoring the tree structure of the network.
In addition, a more powerful version of this protocol - Rapid Spanning Tree Protocol (RSTP, IEEE 802.1w) is implemented in the PSW-2G4F switches, what allows reducing network rebuild time to several milliseconds. When using RSTP, a break in the optics results in a short-term fading of the picture from the video camera (less than 1 second), followed by the restoration of normal operation.
It is recommended to use the RSTP protocol in the ring topology.

Please note that the PSW-2G4F has only 2 Gigabit ports. To connect the video server at maximum speed, you need a 3rd Gigabit port. This means that you will need a switch with 3 Gigabit ports (required with RSTP support). As a rule, this switch should be located in the room next to the video server, so there were no special requirements for the operating conditions.
Note that the IEEE802.w standard does not recommend that you exceed 7 switches in the ring with standard RSTP protocol parameters.
Before installing the PSW-2G4F on an object, you need to locally connect to the device (how to do it, described in detail in the RE) and configure it. First, you need to set up network settings (set a unique IP address, mask, etc.), then enable RSTP (by default, it is off.). Only after this, it is possible to connect the switches into a “ring”. The switch that connects to the video server is recommended to assign the highest priority, so that it becomes ROOT. All management of the PSW-2G4F is done via the WEB interface.
It is important to note that the PSW-2G4F switches support the STP/RSTP protocols in full, so the devices will work not only in the “ring”, but in any topology with redundant connections on any ports.
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