WCF EndpointNotFoundException takes longer than TimeoutException

Question

I'm setup with a group of services that each talk to each other; with the below binding I would have assumed that if I "A" sends a message to "B"(alive) and "C"(not alive) that B would return if processing did not take longer than the sendTimeout defined otherwise it would be a TimeoutException. In the case of "C" that has failed and is not available, I would have assumed it would also return within the sendTimeout defined time. For "B", this seems to be correct but for "C" an EndpointNotFoundException is caught but it takes alot longer than the 5 seconds defined for sendTimeout. Am I missing something in my configuration. The same binding is used for the service and the client

<bindings>
  <netTcpBinding>
    <binding name="SSS" maxBufferPoolSize="524288" maxBufferSize="134217728" maxReceivedMessageSize="134217728" receiveTimeout="infinite" sendTimeout="00:00:05" portSharingEnabled="true">
      <readerQuotas
         maxDepth="32"
         maxStringContentLength="65535"
         maxArrayLength="16384"
         maxBytesPerRead="4096"
         maxNameTableCharCount="16384" />
      <security mode="None">
        <transport clientCredentialType="None" protectionLevel="None"/>
        <message clientCredentialType="None"/>
      </security>
      <reliableSession ordered="true"/>
    </binding>
  </netTcpBinding>
</bindings>


<service behaviorConfiguration="DefaultBehavior" name="hostObj"> 
    <endpoint binding="netTcpBinding" bindingConfiguration="SSS" contract="Contract.IHost" />
  </service>


<endpoint name="serverAppHostEndpoint" binding="netTcpBinding" bindingConfiguration="SSS" contract="Contract.IHost" />


<behaviors>
  <serviceBehaviors>
    <behavior name="DefaultBehavior">
      <!-- To avoid disclosing metadata information, 
      set the value below to false and remove the metadata endpoint above before deployment -->
      <serviceMetadata httpGetEnabled="False" />
      <!-- To receive exception details in faults for debugging purposes, 
      set the value below to true.  Set to false before deployment 
      to avoid disclosing exception information -->
      <serviceDebug includeExceptionDetailInFaults="true" />
    </behavior>
  </serviceBehaviors>
</behaviors>

Answer 1

I'm not 100% sure, but you could be bumping into the fact that when the WCF client executes, time the OS uses to resolve the IP address is not counted towards the SendTimeout setting. You can see further details here: WCF Not Timing out correctly?