YOKOGAWA Vnet/IP, Technical Information

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1. Overview of Vnet/IP
1-11
TI 30A10A05-01E
1.3.3 Achieving high reliability with Ring Configuration
Vnet/IP is a dual-redundant control network. When bus 1 fails, the communication is continued
by switching the route to bus 2. When the bus 1 and bus 2 are installed in parallel, there may
be a case when both of the buses fail at the same time caused by an incident. In such case,
connecting multiple network switches in ring configuration, redundancy of the communication
route can be established. Using this redundant communication route, the communication among
Vnet/IP stations is continued.
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What is Ring network?
Ring network is a network connecting switches in ring configuration. The feature of the ring
network is that having redundant communication routes by its network topology, even one of the
communication routes fails, the rest of the routes continue communications.
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Detouring communication path by Ring network
Suppose a system configuration in which L2SWs are connected in series as shown in the
following figure.
In the system shown in Fig. (1) in which the L2SWs are connected in series, when the
communication failure occurs at one of the L2SWs, the communication among the Vnet/IP
stations are disturbed at the failed L2SW.
However, by connecting among L2SWs “A” to “C” in ring network, as shown in Fig. (2) and (3), to
provide ring protocol settings to the switches, the communication path can be switched to detour
if there is a communication failure point in the communication path.
In this way, the ring network achieves high reliability in communication by redundancy.
(1) An example which L2SWs are connected in series by tree topology.
L2SW B L2SW C L2SW A
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(2) In case where a cable between L2SWs fails in a ring topology network.
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L2SW B L2SW C L2SW A
(3) In case where a L2SW is defective in a ring topology network.
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L2SW B L2SW A L2SW C
Figure Detour of Communication Path by Ring Network
Dec. 26, 2016-00