diff --git a/release/doc/en_US.ISO8859-1/relnotes/article.xml b/release/doc/en_US.ISO8859-1/relnotes/article.xml
index 8234e849dee..a604cd779fc 100644
--- a/release/doc/en_US.ISO8859-1/relnotes/article.xml
+++ b/release/doc/en_US.ISO8859-1/relnotes/article.xml
@@ -290,6 +290,81 @@
       <para revision="263140">Support for the IPX network transport
 	protocol has been removed, and will not be supported in
 	&os;&nbsp;11 and later releases.</para>
+
+      <para revision="272720" contrib="sponsor"
+	sponsor="&limelight;">Support for <acronym>PLPMTUD</acronym>
+	blackhole detection (<acronym>RFC</acronym> 4821) has been
+	added to the &man.tcp.4; stack, disabled by default.  New
+	control tunables have been added:</para>
+
+      <informaltable frame="none" pgwide="0">
+	<tgroup cols="2">
+	  <colspec colwidth="1*"/>
+	  <colspec colwidth="1*"/>
+	  <thead>
+	    <row>
+	      <entry>Tunable</entry>
+	      <entry>Description</entry>
+	    </row>
+	  </thead>
+
+	  <tbody>
+	    <row>
+	      <entry><literal>net.inet.tcp.pmtud_blackhole_detection</literal></entry>
+	      <entry>Enables or disables <acronym>PLPMTUD</acronym>
+		blackhole detection</entry>
+	    </row>
+
+	    <row>
+	      <entry><literal>net.inet.tcp.pmtud_blackhole_mss</literal></entry>
+	      <entry><acronym>MSS</acronym> to try for IPv4</entry>
+	    </row>
+
+	    <row>
+	      <entry><literal>net.inet.tcp.v6pmtud_blackhole_mss</literal></entry>
+	      <entry><acronym>MSS to try for IPv6</acronym></entry>
+	    </row>
+	  </tbody>
+	</tgroup>
+      </informaltable>
+
+      <para>New monitoring &man.sysctl.8;s haven been added:</para>
+
+      <informaltable frame="none" pgwide="0">
+	<tgroup cols="2">
+	  <colspec colwidth="1*"/>
+	  <colspec colwidth="1*"/>
+	  <thead>
+	    <row>
+	      <entry>Tunable</entry>
+	      <entry>Description</entry>
+	    </row>
+	  </thead>
+
+	  <tbody>
+	    <row>
+	      <entry><literal>net.inet.tcp.pmtud_blackhole_activated</literal></entry>
+	      <entry>Number of times the code was activated to attempt
+		downshifting the <acronym>MSS</acronym></entry>
+	    </row>
+
+	    <row>
+	      <entry><literal>net.inet.tcp.pmtud_blackhole_min_activated</literal></entry>
+	      <entry>Number of times the blackhole
+		<acronym>MSS</acronym> was used in an attempt to
+		downshift</entry>
+	    </row>
+
+	    <row>
+	      <entry><literal>net.inet.tcp.pmtud_blackhole_failed</literal></entry>
+	      <entry>Number of times that the blackhole failed to
+		connect after downshifting the
+		<acronym>MSS</acronym></entry>
+	    </row>
+	  </tbody>
+	</tgroup>
+      </informaltable>
+
     </sect3>
 
     <sect3 xml:id="disks">
diff --git a/release/doc/share/xml/sponsor.ent b/release/doc/share/xml/sponsor.ent
index 6e35b8e4868..67720e30411 100644
--- a/release/doc/share/xml/sponsor.ent
+++ b/release/doc/share/xml/sponsor.ent
@@ -23,6 +23,7 @@
 
 <!ENTITY google		"Google">
 
+<!ENTITY limelight	"Limelight Networks">
 <!ENTITY lsi		"LSI">
 
 <!ENTITY netgate	"Netgate">