title: Should I use Request-Id, X-Request-Id or X-Correlation-Id in the request header?
body: <p>I am not clear which id header I should put in the request and response for the correlationship purpose.</p>
  
  <p>"X-Correlation-ID" and the "X-Request-ID" are the known http header.  Does it matter which one I use in the request and response?</p>
  
  <p>ASP.NET Core's System.Diagnostics.DiagnosticSource looks for the "Request-Id".  Is this for the Activity purpose only?  Why doesn't it use the "X-Request-ID"?</p>
  
  <p>If I don't use the Activity, I don't need to send that header, right?   </p>
  
  <p>ASP.NET Core also has the Hierarchical Request-Id (<a href="https://github.com/dotnet/corefx/blob/master/src/System.Diagnostics.DiagnosticSource/src/HierarchicalRequestId.md" rel="noreferrer">https://github.com/dotnet/corefx/blob/master/src/System.Diagnostics.DiagnosticSource/src/HierarchicalRequestId.md</a>
  ) that I like the idea.   I can do something like this</p>
  
  <pre><code>    var newRequestId = $"{context.Request.headers["X-Correlation-ID"]}:{CreateNewGuid()}";
  </code></pre>
  
  <p>OR is it better to use the Activity?  I find the Activity.Current is always null.  Does it need to be enabled and does it affect performance?</p>