&gt; Bullshit. Non-zero in a reserved field that has no meaning now, and should be loudly diagnosed as an error until such a time that it has a meaning.<p>This makes no sense.  You must treat a reserved field as meaningless and having no consequence, otherwise eventually, when it does have meaning and your old code is looking at packets, you&#x27;re going to start &quot;loudly diagnosing&quot; all over the place.