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# 8. The NetworkingBridge Service

The OpenSplice NetworkingBridge is a pluggable service that allows bridging of data between networking services. This section gives an overview of the features of the NetworkingBridge.

The configuration parameters that control the behaviour of the NetworkingBridge are described in the Configuration section.

## 8.1. Background

When a networking service is selected that best suits a specific deployment, sometimes a part of the data needs to be obtained from or disclosed to a system that is using a different kind of networking service. The NetworkingBridge allows `DCPSPublications` and `DCPSSubscriptions` to be matched and the related data forwarded between a RTNetworking system and a DDSI2 system and vice versa.

The NetworkingBridge employs a fast path in the OpenSplice kernel by directly connecting the network queues of the bridged services. This also allows full end-to-end flow control mechanisms to be realised across the bridge. Which publications/subscriptions are bridged can be controlled by means of white- and black-lists.

The NetworkingBridge relies on the discovery of publications and subscriptions by the common means for the networking services. This means that it relies on the real transient topics, aligned by the Durability service, for the RTNetworking part of the bridge. For the part that connects to DDSI2 the native DDSI2 discovery of end-points is used. In order for DDSI2 to only advertise bridged publications and subscriptions, the `LocalDiscoveryPartition` used for regular discovery should be set to a non-existent partition, as can be seen in the following example. This discovery takes some time and can introduce a short delay before data is bridged.

## 8.2. Example Configuration

In order to properly configure the NetworkingBridge for bridging data between RTNetworking and DDSI2, both networking services (and the Durability service for the alignment of the builtin topics of the RTNetworking side) have to be configured. Filtering is also configured with the NetworkingBridge.

An example configuration file for bridging of all data (excluding Topic MyLocalTopic) in partition BridgedPartition is shown below.

    <OpenSplice>
       <Domain>
          <Name>NetworkingBridgeExample</Name>
          <Id>0</Id>
          <Service name="networking">
             <Command>networking</Command>
          </Service>
          <Service name="ddsi2e">
             <Command>ddsi2e</Command>
          </Service>
          <Service name="nwbridge">
            <Command>nwbridge</Command>
          </Service>
          <Service name="durability">
             <Command>durability</Command>
          </Service>
       </Domain>
       <NetworkService name="networking">
          <Partitioning>
             <GlobalPartition Address="broadcast"/>
          </Partitioning>
          <Channels>
             <Channel default="true" enabled="true" name="BestEffort" reliable="false">
                <PortNr>54400</PortNr>
             </Channel>
             <Channel enabled="true" name="Reliable" reliable="true">
                <PortNr>54410</PortNr>
             </Channel>
          </Channels>
          <Discovery enabled="true">
             <PortNr>54420</PortNr>
          </Discovery>
       </NetworkService>
       <DDSI2EService name="ddsi2e">
          <Discovery>
            <LocalDiscoveryPartition>ThisIsNotAPartition</LocalDiscoveryPartition>
          </Discovery>
       </DDSI2EService>
       <NetworkingBridgeService name="nwbridge">
         <Include>
           <!-- Multiple entries can be added here with DCPSPartitionTopic expressions
                on what to include -->
           <Entry DCPSPartitionTopic="BridgedPartition.*"/>
         </Include>
         <Exclude>
           <!-- Multiple entries can be added here with DCPSPartitionTopic expressions
                on what to exclude.
                If a DCPSPublication or DCPSSubscription matches both the include- and
                exclude expressions it will be excluded. -->
           <Entry DCPSPartitionTopic="*.MyLocalTopic"/>
         </Exclude>
       </NetworkingBridgeService>
       <DurabilityService name="durability">
          <Network>
             <Alignment>
                <TimeAlignment>FALSE</TimeAlignment>
                <RequestCombinePeriod>
                   <Initial>2.5</Initial>
                   <Operational>0.1</Operational>
                </RequestCombinePeriod>
             </Alignment>
             <WaitForAttachment maxWaitCount="10">
               <ServiceName>networking</ServiceName>
               <ServiceName>ddsi2e</ServiceName>
             </WaitForAttachment>
          </Network>
          <NameSpaces>
             <NameSpace name="defaultNamespace">
                <Partition>*</Partition>
             </NameSpace>
             <Policy nameSpace="defaultNamespace" durability="Durable"
                               alignee="Initial" aligner="True"/>
          </NameSpaces>
       </DurabilityService>
       <Description>Federated deployment for extending an RTNetworking-based
                    domain into a DDSI network.</Description>
    </OpenSplice>

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