When does open timeout starts ticking on the WCF service? -

i have set open timeout property value service. want know when time starts ticking. when operation called , processing , during idle time after operation returned client. starts ticking after channel or proxy opened using proxy.open()?

following code - client side - proxyclient client = new proxyclient();
var emp = client.getemployee(1);
client.close();

at proxy side code - class proxyclient : clientbase<{interface}>, {interface}
{
protected override iemployee createchannel()
{
thread.sleep(15000);
return base.createchannel();

}
public employee getemployee(int id)
{
var employee = channel.getemployee(id);
return employee;
}
}

looking @ code above, open timeout tick starts. similar question answered closetimeout also.