Add an id attribute to the SSH tunneling section.

Link to this section with an xref element instead
of using ulink.

en_US.ISO8859-1/books/handbook/mail/chapter.sgml

@@ -342,9 +342,8 @@ FreeBSD.org mail is handled (pri=10) by mx1.FreeBSD.org</screen>
 	    username and password credentials in clear-text.  This means
 	    that if you wish to secure the transmission of information
 	    across these protocols, you should consider tunneling
-	    sessions over &man.ssh.1;. See the <ulink
-	    url="../handbook/openssh.html#AEN13610">&os;
-	    handbook</ulink> for more information.</para>
+	    sessions over &man.ssh.1;.  Tunneling sessions is
+	    described in <xref linkend="security-ssh-tunneling">.</para>
         </warning>
       </sect3>
 

en_US.ISO8859-1/books/handbook/security/chapter.sgml

@@ -4810,7 +4810,7 @@ Your identification has been saved in /home/user/.ssh/identity.
 	manual page.</para></warning>
     </sect2>
 
-    <sect2>
+    <sect2 id="security-ssh-tunneling">
       <title>SSH Tunneling</title>
       <indexterm>
         <primary>OpenSSH</primary>