diff --git a/RELEASE_NOTES b/RELEASE_NOTES
index 06562c111..8bee1e782 100644
--- a/RELEASE_NOTES
+++ b/RELEASE_NOTES
@@ -9,8 +9,8 @@ http://www.nsnam.org including tutorials: http://www.nsnam.org/tutorials.html
 Consult the file CHANGES.html for more detailed information about changed
 API and behavior across ns-3 releases.
 
-Release 3-dev
-=============
+Release 3.21
+============
 
 Availability
 ------------
@@ -18,6 +18,13 @@ This release is not yet available.
 
 Supported platforms
 -------------------
+- Fedora Core 20 (32/64 bit) with g++-4.8.2
+- Ubuntu 14.04 (32/64 bit) with g++-4.8.2
+- Ubuntu 12.04.4 (64 bit) with g++-4.6.3
+- Ubuntu 10.04.4 LTS (64 bit) with g++-4.4.3
+- CentOS/RHEL 6.5 (64-bit) with g++-4.4.7
+- OS X Mavericks 10.9 with Xcode 5.1.1 and clang-503.0.40
+- FreeBSD 9.2-RELEASE (64 bit) with clang-3.3
 
 New user-visible features
 -------------------------
@@ -39,17 +46,25 @@ New user-visible features
    - updated RadioEnvironmentMapHelper. Now RadioEnvironmentMap can be generated 
      for Data or Control channel and for specified RbId, what is helpful when 
      using FR algorithms
-- SimpleNetDevice and SimpleChannel are not so simple anymore. 
-  SimpleNetDevice can be now a Broadcast or PointToPoint NetDevice, 
-  it can have a limited bandwidth and it uses an output queue.
+- Added a CoDel queue model.  CoDel queues measure and control the queue
+  traversal delay.  The ns-3 implementation is a port of the Linux 
+  implementation.
+- Added support for TCP timestamp and window scale options, and added
+  ability to trace the TCP slow start threshold value.
+- SimpleNetDevice and SimpleChannel (used for adding basic link effects
+  for testing of higher-layer protocols) have been extended to support 
+  the option of broadcast or PointToPoint link semantics.  The bandwidth
+  and link delay can be constrained, and it uses an output queue.
 - SimpleNetDevice and SimpleChannel can be installed in a node through 
-  an helper: SimpleNetDeviceHelper.
+  a new helper: SimpleNetDeviceHelper.
 - Implemented new PacketSocketServer and PacketSocketClient applications.
-  The primary use is in tests, to avoid the ones from the application module.
+  The primary use is in tests, to avoid using the ones from the 
+  application module that also bring in a dependency on the internet module.
   
 Bugs fixed
 ----------
 
+- Bug 1673 - Config::Set/Connect does not search for attributes in parent class
 - Bug 1762 - UE stuck in IDLE_CONNECTING because RRC CONN REQ is not transmitted
 - Bug 1811 - basic traffic generator for network module 
 - Bug 1824 - L4 protocol sockets should support BindToNetDevice over IPv6
@@ -59,6 +74,7 @@ Bugs fixed
 - Bug 1858 - wireless examples not correctly recording packet reception
 - Bug 1860 - TCP needs the Window Scale option
 - Bug 1893 - issue in DoSchedUlTriggerReq with harq
+- Bug 1911 - AODV cannot work on nodes with more than one netdevice
 - Bug 1921 - Icmpv6L4Protocol::ForgeEchoRequest returns a malformed packet
 - Bug 1930 - Use of invalid reference in OLSR RemoveLinkTuple
 - Bug 1932 - NdiscCache entry is not failsafe on double neighbor probing.
@@ -70,11 +86,15 @@ Bugs fixed
 - Bug 1960 - Wrong information on index range, about Node::GetDevice
 - Bug 1961 - planetlab-tap-creator "variable set but not used"
 - Bug 1963 - AODV can tag the same packet twice (and raise an assert)
+- Bug 1964 - Integer overflow on UniformRandomVariable::GetInteger()
 - Bug 1967 - LL Multicast is not compressed in the right way in IPHC
 - Bug 1981 - PyViz shell not compatible with ipython >= 0.11
 
 Known issues
 ------------
+- Bug 1770 - The mesh module will crash if used for g++ version >= 4.8.1
+in optimized mode, on a 32-bit Linux machine.  Lowering the optimization
+level to -O1 in this case can be used as a workaround.
 
 Release 3.20
 =============