consolidate docs (#3423)

Author: mairaw

xml/System.Net/HttpListener.xml

@@ -34,7 +34,8 @@
     <remarks>
       <format type="text/markdown"><![CDATA[  
   
-## Remarks  
+## Remarks
+
  Using the <xref:System.Net.HttpListener> class, you can create a simple HTTP protocol listener that responds to HTTP requests. The listener is active for the lifetime of the <xref:System.Net.HttpListener> object and runs within your application with its permissions.
    
  To use <xref:System.Net.HttpListener>, create a new instance of the class using the <xref:System.Net.HttpListener> constructor and use the <xref:System.Net.HttpListener.Prefixes%2A> property to gain access to the collection that holds the strings that specify which Uniform Resource Identifier (URI) prefixes the <xref:System.Net.HttpListener> should process.
@@ -66,8 +67,12 @@
   
 > [!NOTE]
 > If you specify multiple authentication schemes for the <xref:System.Net.HttpListener>, the listener will challenge clients in the following order: `Negotiate`, `NTLM`, `Digest`, and then `Basic`.
-  
-   
+
+### HTTP.sys
+
+The <xref:System.Net.HttpListener> class is built on top of `HTTP.sys`, which is the kernel mode listener that handles all HTTP traffic for Windows.
+`HTTP.sys` provides connection management, bandwidth throttling, and web server logging.
+Use the [HttpCfg.exe](/windows/win32/http/httpcfg-exe) tool to add SSL certificates.
   
 ## Examples
  The following code example demonstrates using a <xref:System.Net.HttpListener>.  
@@ -77,7 +82,8 @@
   
  ]]></format>
     </remarks>
-    <related type="Article" href="https://msdn.microsoft.com/library/8bf0b428-5a21-4299-8d6e-bf8251fd978a">Changes to NTLM authentication for HTTPWebRequest in Version 3.5 SP1</related>
+    <related type="Article" href="~/docs/framework/network-programming/changes-to-ntlm-authentication-for-httpwebrequest-in-version-3-5-sp1.md">Changes to NTLM authentication for HTTPWebRequest in Version 3.5 SP1</related>
+    <related type="Article" href="/windows/win32/http/httpcfg-exe">HttpCfg.exe</related>
   </Docs>
   <Members>
     <Member MemberName=".ctor">