title: Silent Push Notification in iOS 7 does not work
body: <p>In the WWDC 2013's "What's New with Multitasking" presentation, there is a section about Silent Push Notifications.  It seems straight forward.  According to the presentation, if you send the APS payload with just the content-available set to 1, users will not be notified of the notification.</p>
  
  <pre><code>// A. This doesn't work
  { 
    aps: { 
            content-available: 1 
         }
  }
  </code></pre>
  
  <p>My testing shows that this does not work as no push is received.  But if I include the sound attribute but exclude the alert attribute, it works (though not silent anymore).</p>
  
  <pre><code>// B. This works
  { 
    aps: {
            content-available: 1,
            sound: "default"
         }
  }
  </code></pre>
  
  <p>However, if I change the sound attribute to play a silent audio, I can mimic a silent push.</p>
  
  <pre><code>// C. This works too.
  { 
    aps: {
            content-available: 1,
            sound: "silence.wav"
         }
  }
  </code></pre>
  
  <p>Does anyone know:</p>
  
  <ol>
  <li>If this a bug?</li>
  <li>And if it is correct to assume that B or C is being treated as a Remote Notification (and not a bug with Silent Push where you need a sound attribute)? If so, this means it is not rate limited like Silent Pushes are... which Apple will likely fix.  So I probably should not rely on it.</li>
  <li>What the rate limit is (N pushes every X seconds, etc)?</li>
  </ol>
  
  <p>Thanks in advance.</p>
  
  <p><strong>Edit with more information</strong></p>
  
  <p>For A, the state of the application does not matter.  Notification is never received.</p>
  
  <p>It seems like B and C only work if you enclose the attributes and values in quotes, like below.</p>
  
  <pre><code>{"aps":{"content-available": 1, "sound":"silent.wav"}}
  </code></pre>
  
  <p>And the notification arrives in <strong>application:didReceiveRemoteNotification:fetchCompletionHandler:</strong> regardless of state.</p>