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RipEX in detail
Note
Limited broadcast 255.255.255.255 and Direct broadcast e.g. 192.168.255.255 as well as
Multicast (224.0.0.0 through 239.255.255.255) on Ethernet are supported and transferred
over the network.
You can see an instructional video explaining the Bridge mode functionality here: http://www.ra-
com.eu/ripex-bridge-mode
2.2.1. Detailed Description
Bridge mode is suitable for Point-to-Multipoint networks, where Master-Slave applications with polling-
type communication protocol are used. RipEX in bridge mode is as easy to use as a simple transparent
device, while providing communication reliability and spectrum efficiency by employing a sophisticated
protocol in the radio channel.
In bridge mode, the radio channel protocol does not solve collisions. There is a CRC check of data in-
tegrity, however, i.e. once a message is delivered, it is 100% error free.
All the messages received from user interfaces (ETH&COM) are immediately transmitted to the radio
channel.
ETH - The whole network of RipEX radiomodems behaves as a standard Ethernet network bridge.
Each ETH interface automatically learns which devices (MAC addresses) are located in the local LAN
and which devices are accessible over the radio channel. Consequently, only the Ethernet frames ad-
dressed to remote devices are physically transmitted on the radio channel. This arrangement saves
the precious RF spectrum from extra load which would be otherwise generated by local traffic in the
LAN (the LAN to which the respective ETH interface is connected).
One has to be very careful when RipEX in Bridge mode is connected to LAN, because all LAN traffic
is then broadcast to the Radio channel.
COM1,COM2 - All frames received from COM1(2) are broadcast over the radio channel and transmitted
to all COM ports (COM1 as well as COM2) on all radio modems within the network, the other COM on
the source RipEX excluding.
There is a special parameter TX delay (Adv. Config., Device), which should be used when all substations
(RTU) reply to a broadcast query from the master station. In such case massive collisions would ensue
because all substations (RTU) would reply at nearly the same time. To prevent such collision, TX delay
should be set individually in each slave RipEX. The length of responding frame, the length of radio
protocol overhead, modulation rate have to be taken into account.
2.2.2. Functionality example
In the following, common acronyms from SCADA systems are used:
•
FEP - Front End Processor, designates the communication interface equipment in the centre
•
RTU - Remote Telemetry Unit, the terminal SCADA equipment at remote sites
The single digits in illustrations are "site names" and do not necessarily correspond with actual addresses
of both the RipEX's and SCADA equipment. Address configuration examples are given in the next
chapter.
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RipEX Radio modem & Router – © RACOM s.r.o.
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