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<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<title>ns-3 Change Log</title>
</head>
<body>
<h1>
ns-3: API and model change history</h1>
<!--
This ChangeLog is updated in the reverse order
with the most recent changes coming first. Date format: DD-MM-YYYY
-->
<p>
ns-3 is an evolving system and there will be API or behavioral changes
from time to time. Users who try to use scripts or models across
versions of ns-3 may encounter problems at compile time, run time, or
may see the simulation output change. </p>
<p>
We have adopted the development policy that we are going to try to ease
the impact of these changes on users by documenting these changes in a
single place (this file), and not by providing a temporary or permanent
backward-compatibility software layer. </p>
<p>
A related file is the RELEASE_NOTES file in the top level directory.
This file complements RELEASE_NOTES by focusing on API and behavioral
changes that users upgrading from one release to the next may encounter.
RELEASE_NOTES attempts to comprehensively list all of the changes
that were made. There is generally some overlap in the information
contained in RELEASE_NOTES and this file. </p>
<p>
The goal is that users who encounter a problem when trying to use older
code with newer code should be able to consult this file to find
guidance as to how to fix the problem. For instance, if a method name
or signature has changed, it should be stated what the new replacement
name is. </p>
<p>
Note that users who upgrade the simulator across versions, or who work
directly out of the development tree, may find that simulation output
changes even when the compilation doesn't break, such as when a
simulator default value is changed. Therefore, it is good practice for
_anyone_ using code across multiple ns-3 releases to consult this file,
as well as the RELEASE_NOTES, to understand what has changed over time.
</p>
<p>
This file is a best-effort approach to solving this issue; we will do
our best but can guarantee that there will be things that fall through
the cracks, unfortunately. If you, as a user, can suggest improvements
to this file based on your experience, please contribute a patch or drop
us a note on ns-developers mailing list.</p>
<hr>
<h1>Changes from ns-3.34 to ns-3.35</h1>
<h2>New API:</h2>
<ul>
<li>In class <b>Ipv6Header</b>, new functions SetSource (), SetDestination (), GetSource () and GetDestination () are added, consistent with <b>Ipv4Header</b>. The existing functions had "Address" suffix in each of the function names, and are are deprecated now.</li>
<li>In class <b>Ipv4InterfaceAddress</b>, new functions SetAddress () and GetAddress () are added, corresponding to SetLocal () and GetLocal () respectively. This is done to keep consistency with <b>Ipv4InterfaceAddress</b>.</li>
<li>With the new support for IPv6 Nix-Vector routing, we have all the new APIs corresponding to IPv4 Nix-Vector routing. Specific to the user, there is an Ipv6NixVectorHelper class which can be set in the InternetStackHelper, and works similar to Ipv4NixVectorHelper.</li>
<li>In class <b>Ipv4InterfaceAddress</b>, a new function IsInSameSubnet () is added to check if both the IPv4 addresses are in the same subnet. Also, it is consistent with <b>Ipv6InterfaceAddress::IsInSameSubnet ()</b>.</li>
<li>In class <b>ConfigStore</b>, a new Attribue <b>SaveDeprecated</b> allows to not save DEPRECATED Attributes. The default value is <b>false</b> (save DEPRECATED Attributes).</li>
<li>In class <b>TracedCallback</b>, a new function <b>IsEmpty</b> allows to know if the TracedCallback will call any callback.</li>
<li>A new specialization of std::hash for Ptr allows one to use Ptrs as keys in unordered_map and unordered_set containers.</li>
<li>A new <b>GroupMobilityHelper</b> mobility helper has been added to ease the configuration of group mobility (a form of hierarchical mobility in which multiple child mobility models move with reference to an underlying parent mobility model). New example programs and animation scripts are also added to both the buildings and mobility modules.</li>
</ul>
<h2>Changes to existing API:</h2>
<ul>
<li>In class <b>Ipv6Header</b>, the functions SetSourceAddress (), SetDestinationAddress (), GetSourceAddress () and GetDestinationAddress () are deprecated. New corresponding functions are added by removing the "Address" suffix. This change is made for having consistency with <b>Ipv4Header</b>.</li>
<li><b>ipv4-nix-vector-helper.h</b> and <b>ipv4-nix-vector-routing.h</b> have been deprecated in favour of <b>nix-vector-helper.h</b> and <b>nix-vector-routing.h</b> respectively.</li>
</ul>
<h2>Changes to build system:</h2>
<ul>
<li>The default C++ standard is now C++17.</li>
<li>The minimum compiler versions have been raised to g++-7 and clang-10 (Linux) and Xcode 11 (macOS).</li>
</ul>
<h2>Changed behavior:</h2>
<ul>
<li>Nix-Vector routing supports topologies with multiple WiFi networks using the same WiFi channel object.</li>
<li>ConfigStore no longer saves OBSOLETE attributes.</li>
<li>The <b>Ipv4L3Protocol</b> Duplicate detection now accounts for transmitted packets, so a transmitting multicast node will not forward its own packets.</li>
<li>Wi-Fi: A-MSDU aggregation now implies that constituent MSDUs are immediately dequeued
from the EDCA queue and replaced by an MPDU containing the A-MSDU. Thus, aggregating N
MSDUs triggers N dequeue operations and 1 enqueue operation on the EDCA queue.</li>
<li>Wi-Fi: MPDUs being passed to the PHY layer for transmission are not dequeued, but
are kept in the EDCA queue until they are acknowledged or discarded. Consequently, the
BlockAckManager retransmit queue has been removed.</li>
</ul>
<hr>
<h1>Changes from ns-3.33 to ns-3.34</h1>
<h2>New features and API:</h2>
<ul>
<li>Support for Wi-Fi <b>802.11ax downlink and uplink OFDMA</b>, including multi-user OFDMA and a <b>round-robin multi-user scheduler</b>.</li>
<li><b>FqCobalt</b> queue disc with L4S features and set associative hash.</li>
<li><b>FqPIE</b> queue disc with L4S mode</li>
<li><b>ThompsonSamplingWifiManager</b> Wi-Fi rate control algorithm.</li>
<li>New <b>PhasedArrayModel</b>, providing a flexible interface for modeling a number of Phase Antenna Array (PAA) models.</li>
<li>Added the ability to configure the <b>Wi-Fi primary 20 MHz channel</b> for 802.11 devices operating on channels of width greater than 20 MHz.</li>
<li>A <b>TCP BBRv1</b> congestion control model.</li>
<li><b>Improved support for bit fields</b> in header serialization/deserialization.</li>
<li>Support for <b>IPv6 stateless address auto-configuration (SLAAC)</b>.</li>
</ul>
<h2>Changes to existing API:</h2>
<ul>
<li>The <b>WifiAckPolicySelector</b> class has been replaced by the <b>WifiAckManager</b> class. Correspondingly, the ConstantWifiAckPolicySelector has been replaced by the WifiDefaultAckManager class. A new WifiProtectionManager abstract base class and WifiDefaultProtectionManager concrete class have been added to implement different protection policies.</li>
<li>The class <b>ThreeGppAntennaArrayModel</b> has been replaced by <b>UniformPlanarArray</b>, extending the PhasedArrayModel interface.</li>
<li>The <b>Angles struct</b> is now a class, with robust setters and getters (public struct variables phi and theta are now private class variables m_azimuth and m_inclination), overloaded operator<< and operator>> and a number of utilities.</li>
<li><b>AntennaModel</b> child classes have been extended to produce 3D radiation patterns. Attributes such as Beamwidth have thus been separated into Vertical/HorizontalBeamwidth.</li>
<li>The attribute <b>UseVhtOnly</b> in <b>MinstrelHtWifiManager</b> has been replaced by a new attribute called <b>UseLatestAmendmentOnly</b>.
<li> The wifi module has <b>removed HT Greenfield support, Holland (802.11a-like) PHY configuration, and Point Coordination Function (PCF)</b></li>
<li> The wifi ErrorRateModel API has been extended to support <b>link-to-system models</b>.
<li> <b>Nix-Vector routing</b> supports multiple interface addresses and can print out routing paths</b>.
<li>The <b>TxOkHeader and TxErrHeader trace sources</b> of RegularWifiMac have been obsoleted and replaced by trace sources that better capture the result of a transmission: AckedMpdu (fired when an MPDU is successfully acknowledged, via either a Normal Ack or a Block Ack), NAckedMpdu (fired when an MPDU is negatively acknowledged via a Block Ack), DroppedMpdu (fired when an MPDU is dropped), MpduResponseTimeout (fired when a CTS is missing after an RTS or a Normal Ack is missing after an MPDU) and PsduResponseTimeout (fired when a BlockAck is missing after an A-MPDU or a BlockAckReq).</li>
</ul>
<h2>Changes to build system:</h2>
<ul>
<li> The handling of <b>Boost library/header dependencies</b> has been improved.</li>
</ul>
<h2>Changed behavior:</h2>
<ul>
<li>The default <b>TCP congestion control</b> has been changed from NewReno to CUBIC.</li>
<li>The <b>PHY layer of the wifi module</b> has been refactored: the amendment-specific logic has been ported to <b>PhyEntity</b> classes and <b>WifiPpdu</b> classes.</li>
<li>The <b>MAC layer of the wifi module</b> has been refactored. The MacLow class has been replaced by a hierarchy of FrameExchangeManager classes, each adding support for the frame exchange sequences introduced by a given amendment.</li>
<li>The <b>wifi BCC AWGN error rate tables</b> have been aligned with the ones provided by MATLAB and users may note a few dB difference when using BCC at high SNR and high MCS.</li>
<li><b>ThreeGppChannelModel has been fixed</b>: cluster and sub-cluster angles could have been generated with inclination angles outside the inclination range [0, pi], and have now been constrained to the correct range.</li>
<li>The <b>LTE RLC Acknowledged Mode (AM) transmit buffer</b> is now limited by default to a size of (1024 * 10) bytes. Configuration of unlimited behavior can still be made by passing the value of zero to the new attribute <b>MaxTxBufferSize</b>.</li>
</ul>
<hr>
<h1>Changes from ns-3.32 to ns-3.33</h1>
<h2>New API:</h2>
<ul>
<li>A model for <b>TCP CUBIC</b> (RFC 8312) has been added.</li>
<li>New <b>channel models based on 3GPP TR 37.885</b> have been added to support vehicular simulations.</li>
<li><b>Time::RoundTo (unit)</b> allows time to be rounded to the nearest integer multiple of unit</li>
<li><b>UdpClient</b> now can report both transmitted and received bytes.</li>
<li>A new <b>MPI Enable()</b> variant was introduced that takes a user-supplied MPI_Communicator, allowing for partitioning of the MPI processes.</li>
<li>A <b>Length</b> class has been introduced to allow users to replace the use of raw numbers (ints, doubles) that have implicit lengths with a class that represents lengths with an explicit unit.</li>
<li>A flexible <b>CsvReader</b> class has been introduced to allow users to read in csv- or tab-delimited data.</li>
<li>The <b>ListPositionAllocator</b> can now input positions from a csv file.</li>
<li>A new trace source for DCTCP alpha value has been added to <b>TcpDctcp</b>.</li>
<li>A new <b>TableBasedErrorRateModel</b> has been added for Wi-Fi, and the default values are aligned with link-simulation results from MATLAB WLAN Toolbox and IEEE 802.11 TGn.
</li>
<li>A new <b>LdpcSupported</b> attribute has been added for Wi-Fi in <b>HtConfiguration</b>, in order to select LDPC FEC encoding instead of the default BCC FEC encoding.
</li>
</ul>
<h2>Changes to existing API:</h2>
<ul>
<li> The signature of <b>WifiPhy::PsduTxBeginCallback</b> and <b>WifiPhy::PhyTxPsduBegin</b> have been changed to take a map of PSDUs instead of a single PSDU
in order to support multi-users (MU) transmissions.
</li>
<li> The wifi trace <b>WifiPhy::PhyRxBegin</b> has been extended to report the received power for every band.
</li>
<li> The wifi trace <b>WifiPhy::PhyRxBegin</b> has been extended to report the received power for every band.
</li>
<li>New attributes <b>SpectrumWifiPhy::TxMaskInnerBandMinimumRejection</b>, <b>SpectrumWifiPhy::TxMaskOuterBandMinimumRejection</b> and <b>SpectrumWifiPhy::TxMaskOuterBandMaximumRejection</b> have been added to configure the OFDM transmit masks.
</li>
</ul>
<h2>Changes to build system:</h2>
<ul>
<li>Waf has been upgraded to git development version waf-2.0.21-6-g60e3f5f4</li>
</ul>
<h2>Changed behavior:</h2>
<ul>
<li>The <b>default Wi-Fi ErrorRateModel</b> for the 802.11n/ac/ax standards has been changed from the NistErrorRateModel to a new TableBasedErrorRateModel. Users may experience a shift in Wi-Fi link range due to the new default error model, as <b>the new model is more optimistic</b> (the PER for a given MCS will degrade at a lower SNR value). The Wi-Fi module documentation provides plots that compare the performance of the NIST and new table-based model.</li>
<li>The default value of the <b>BerThreshold</b> attribute in <b>IdealWifiManager</b> was changed from 1e-5 to 1e-6, so as to correct behavior with high order MCS.</li>
<li> <b>Time values that are created from an int64x64_t value</b> are now rounded to the nearest integer multiple of the unit, rather than truncated. Issue #265 in the GitLab.com tracker describes the behavior that was fixed. Some Time values that rely on this conversion may have changed due to this fix.</li>
<li> TCP now implements the Linux-like <b>congestion window reduced (CWR)</b> state when explicit congestion notification (ECN) is enabled.</li>
<li> <b>TcpDctcp</b> now inherits from <b>TcpLinuxReno</b>, making its congestion avoidance track more closely to that of Linux.</li>
</ul>
<hr>
<h1>Changes from ns-3.31 to ns-3.32</h1>
<h2>New API:</h2>
<ul>
<li>A new TCP congestion control, <b>TcpLinuxReno</b>, has been added.</li>
<li>Added, to <b>PIE queue disc</b>, <b>queue delay calculation using timestamp</b> feature (Linux default behavior), <b>cap drop adjustment</b> feature (Section 5.5 of RFC 8033), <b>ECN</b> (Section 5.1 of RFC 8033) and <b>derandomization</b> feature (Section 5.4 of RFC 8033).</li>
<li>Added <b>L4S Mode</b> to FqCoDel and CoDel queue discs</li>
<li> A model for <b>dynamic pacing</b> has been added to TCP.</li>
<li>Added <b>Active/Inactive feature</b> to PIE queue disc</li>
<li>Added <b>netmap</b> and <b>DPDK</b> emulation device variants</li>
<li>Added capability to configure <b>STL pair and containers as attributes</b></li>
<li> Added <b>CartesianToGeographic</b> coordinate conversion capability</li>
<li> Added <b>LollipopCounter</b>, a sequence number counter type</li>
<li> Added <b>6 GHz band</b> support for Wi-Fi 802.11ax</li>
</ul>
<h2>Changes to existing API:</h2>
<ul>
<li>The <b>Sifs</b>, <b>Slot</b> and <b>Pifs</b> attributes have been moved from <b>WifiMac</b> to <b>WifiPhy</b> to better reflect that they are PHY characteristics, to decouple the MAC configuration from the PHY configuration and to ease the support for future standards.</li>
<li>The Histogram class was moved from the flow-monitor module to the stats
module to make it more easily accessed. If you previously used Histogram by
by including flow-monitor.h you will need to change that to stats-module.h.
</li>
<li>The <b>WifiHelper::SetStandard (WifiPhyStandard standard)</b> method no
longer takes a WifiPhyStandard enum, but instead takes a similarly named
WifiStandard enum. If before you specified a value such as WIFI_PHY_STANDARD_xxx, now you must specify WIFI_STANDARD_xxx.
</li>
<li> The <b>YansWifiPhyHelper::Default</b> and <b>SpectrumWifiPhyHelper::Default</b> methods have been removed; the default constructors may instead by used.</li>
<li> <b>PIE</b> queue disc now uses <b>Timestamp</b> for queue delay calculation as default instead of <b>Dequeue Rate Estimator</b></li>
</ul>
<h2>Changes to build system:</h2>
<ul>
<li>Added "--enable-asserts" and "--enable-logs" to waf configure, to selectively enable asserts and/or logs in release and optimized builds.</li>
<li>A build version reporting system has been added by extracting data from the
local git repository (or a standalone file if a git repository is not present). </li>
<li>Added support for EditorConfig</li>
</ul>
<h2>Changed behavior:</h2>
<ul>
<li>Support for <b>RIFS</b> has been dropped from wifi. RIFS has been obsoleted by the 802.11 standard and support for it was not implemented according to the standard.</li>
<li>The default loss recovery algorithm for TCP has been changed from Classic Recovery to Proportional Rate Reduction (PRR).</li>
<li>The behavior of <b>TcpPrrRecovery</b> algorithm was aligned to that of Linux.</li>
<li> <b>PIE</b> queue disc now uses <b>Timestamp</b> for queue delay calculation as default instead of <b>Dequeue Rate Estimator</b></li>
<li>TCP pacing, when enabled, now adjusts the rate dynamically based on the window size, rather than just enforcing a constant rate.</li>
<li>WifiPhy forwards up MPDUs from an A-MPDU under reception as long as they arrive at the PHY, instead of forwarding up the whole A-MPDU once its reception is completed.</li>
<li>The ns-3 TCP model was changed to set the initial congestion window to 10 segments instead of 1 segment (to align with default Linux configuration).</li>
</ul>
<hr>
<h1>Changes from ns-3.30 to ns-3.31</h1>
<h2>New API:</h2>
<ul>
<li> A <b>TCP DCTCP</b> model has been added.</li>
<li> <b>3GPP TR 38.901</b> pathloss, channel condition, antenna array, and fast fading models have been added.</li>
<li> New <b>...FailSafe ()</b> variants of the <b> Config </b> and <b>Config::MatchContainer</b> functions which set Attributes or connect TraceSources. These all return a boolean indicating if any attributes could be set (or trace sources connected). These are useful if you are not sure that the requested objects exist, for example in AnimationInterface.</li>
<li> New attributes for <b> Ipv4L3Protocol</b> have been added to enable RFC 6621-based duplicate packet detection (DPD) (<b>EnableDuplicatePacketDetection</b>) and to control the cache expiration time (<b>DuplicateExpire</b>).</li>
<li><b> MakeConsistent </b> method of <b> BuildingsHelper </b> class is
deprecated and moved to <b> MobilityBuildingInfo </b> class. <b> DoInitialize </b>
method of the <b> MobilityBuildingInfo </b> class would be responsible for making
the mobility model of a node consistent at the beginning of a simulation.
Therefore, there is no need for an explicit call to <b> MakeConsistent </b> in a simulation script.</li>
<li> The <b> IsInside </b> method of <b> MobilityBuildingInfo </b> class is extended
to make the mobility model of a moving node consistent.</li>
<li> The <b> IsOutside </b> method of <b> MobilityBuildingInfo </b> class is
deprecated. The <b> IsInside </b> method should be use to check the position of a node.</li>
<li>A new abstract base class, <b>WifiAckPolicySelector</b>, is introduced to implement
different techniques for selecting the acknowledgment policy for PSDUs containing
QoS Data frames. Wifi, mesh and wave helpers provide a SetAckPolicySelectorForAc
method to configure a specific ack policy selector for a given Access Category.</li>
<ul>
<li>The default ack policy selector is named <b>ConstantWifiAckPolicySelector</b>, which
allows to choose between Block Ack policy and Implicit Block Ack Request policy and
allows to request an acknowledgment after a configurable number of MPDUs have been
transmitted.</li>
</ul>
<li>The <b>MaxSize</b> attribute is removed from the <b>QueueBase</b> base class and moved to subclasses. A new MaxSize attribute is therefore added to the DropTailQueue class, while the MaxQueueSize attribute of the WifiMacQueue class is renamed as MaxSize for API consistency.</li>
<li> Two new <b>Application sequence number and timestamp</b> variants have been added, to support packet delivery tracing.
<ul>
<li> A new sequence and timestamp header variant for applications has been added. The <b>SeqTsEchoHeader</b> contains an additional timestamp field for use in echoing a timestamp back to a sender.</li>
<li> TCP-based applications (OnOffApplication, BulkSendApplication, and PacketSink) support a new header, <b>SeqTsSizeHeader</b>, to convey sequence number, timestamp, and size data. Use is controlled by the "EnableSeqTsSizeHeader" attribute.</li>
</ul>
<li>Added a new trace source <b>PhyRxPayloadBegin</b> in WifiPhy for tracing begin of PSDU reception.</li>
<li>Added the class <b>RandomWalk2dOutdoorMobilityModel</b> that models a random walk which does not enter any building.</li>
<li>Added support for the <b>Cake set-associative hash</b> in the FqCoDel queue disc</li>
<li>Added support for <b>ECN marking for CoDel and FqCoDel</b> queue discs</li>
</ul>
<h2>Changes to existing API:</h2>
<ul>
<li> The API for <b>enabling and disabling ECN</b> in TCP sockets has been refactored.</li>
<li> The <b>LTE HARQ</b> related methods in LteEnbPhy and LteUePhy have been renamed, and the LteHelper updated.</li>
<li> Previously the <b>Config::Connect</b> and <b>Config::Set</b> families of functions would fail silently if the attribute or trace source didn't exist on the path given (typically due to spelling errors). Now those functions will throw a fatal error. If you need the old behavior use the new <b>...FailSafe ()</b> variants.</li>
<li>The internal TCP API for <b>TcpCongestionOps</b> has been extended to support the <b>CongControl</b> method to allow for delivery rate estimation feedback to the congestion control mechanism.</li>
<li>Functions <b>LteEnbPhy::ReceiveUlHarqFeedback</b> and <b>LteUePhy::ReceiveLteDlHarqFeedback</b> are renamed to <b>LteEnbPhy::ReportUlHarqFeedback</b> and <b>LteUePhy::EnqueueDlHarqFeedback</b>, respectively to avoid confusion about their functionality. <b>LteHelper</b> is updated accordingly.</li>
<li>Now on, instead of <b>uint8_t</b>, <b>uint16_t</b> would be used to store a bandwidth value in LTE.</li>
<li>The preferred way to declare instances of <b>CommandLine</b> is now through a macro: <b>COMMANDLINE (cmd)</b>. This enables us to add the <b>CommandLine::Usage()</b> message to the Doxygen for the program.</li>
<li>New <b>...FailSafe ()</b> variants of the <b> Config </b> is used to connect PDCP TraceSources of eNB and UE in <b>RadioBearerStatsConnector</b> class. It is required for the simulations using RLC SM where PDCP objects are not created for data radio bearers.</li>
<li><b>T310</b> timer in <b>LteUeRrc</b> class is stopped if the UE receives <b>RRCConnectionReconfiguration</b> including the <b>mobilityControlInfo</b>. This change is introduced following the 3GPP standard TS36331 sec 5.3.5.4.</li>
<li>The wifi <b>High Latency tags</b> have been removed. The only rate manager (Onoe) that was making use of them has been refactored.</li>
<li>The wifi <b>MIMO diversity model</b> has been changed to better fit with MRC theory for AWGN channels when STBC is not used (since STBC is currently not supported).</li>
<li> The <b>BuildingsHelper::MakeMobilityModelConsistent()</b> method is deprecated in favor of MobilityBuildingInfo::MakeConsistent</li>
<li> The <b>MobilityBuildingInfo::IsOutdoor ()</b> method is deprecated; use the result of IsIndoor() method instead</li>
<li> IsEqual() methods of class <b>Ipv4Address, Ipv4Mask, Ipv6Address, and Ipv6Prefix</b> are deprecated.</li>
<li> The API around the <b>wifi Txop class</b> was refactored.</li>
</ul>
<h2>Changes to build system:</h2>
<ul>
<li>The <b>--lcov-report</b> option to Waf was fixed, and a new <b>--lcov-zerocounters</b> option was added to improve support for lcov.</li>
<li>Python bindings were enabled for <b>netanim</b>.</li>
</ul>
<h2>Changed behavior:</h2>
<ul>
<li> The <b>EmpiricalRandomVariable</b> no longer linearly interpolates between values by default, but instead will default to treating the CDF as a histogram and return one of the specific inputs. The previous interpolation mode can be configured by an attribute.</li>
<li> (as reported above) previously the <b>Config::Connect</b> and <b>Config::Set</b> families of functions would fail silently if the attribute or trace source didn't exist on the path given (typically due to spelling errors). Now those functions will throw a fatal error. If you need the old behavior use the new <b>...FailSafe ()</b> variants.</li>
<li> Attempting to deserialize an enum name which wasn't registered with <b>MakeEnumChecker</b> now causes a fatal error, rather failing silently. (This can be triggered by setting an enum Attribute from a StringValue.)</li>
<li> As a result of the above API changes in <b> MobilityBuildingInfo </b>
and <b> BuildingsHelper </b> classes, a building aware pathloss models, e.g.,
<b> HybridBuildingsPropagationLossModel </b> is now able to accurately compute
the pathloss for a node moving in and out of buildings in a simulation. See <a href=https://gitlab.com/nsnam/ns-3-dev/issues/80>issue 80</a>
for discussion.</li>
<li> The implementation of the <b>Wi-Fi channel access</b> functions has been improved
to make them more conformant to the IEEE 802.11-2016 standard. Concerning the DCF,
the backoff procedure is no longer invoked when a packet is queued for transmission
and the medium has not been idle for a DIFS, but it is invoked if the medium is busy
or does not remain idle for a DIFS after the packet has been queued. Concerning the
EDCAF, tranmissions are now correctly aligned at slot boundaries.</li>
<li> Various wifi physical layer behavior around channel occupancy calculation, phy state calculation, and handling different channel widths has been updated.</li>
</ul>
<hr>
<h1>Changes from ns-3.29 to ns-3.30</h1>
<h2>New API:</h2>
<ul>
<li>Added the attribute <b>Release</b> to the class <b>EpsBearer</b>, to select the release (e.g., release 15)</li>
<li>The attributes <b>RegularWifiMac::HtSupported</b>, <b>RegularWifiMac::VhtSupported</b>, <b>RegularWifiMac::HeSupported</b>, <b>RegularWifiMac::RifsSupported</b>, <b>WifiPhy::ShortGuardEnabled</b>, <b>WifiPhy::GuardInterval</b> and <b>WifiPhy::GreenfieldEnabled</b> have been deprecated. Instead, it is advised to use <b>WifiNetDevice::HtConfiguration</b>, <b>WifiNetDevice::VhtConfiguration</b> and <b>WifiNetDevice::HeConfiguration</b>.</li>
<li>The attributes <b>{Ht,Vht,He}Configuration::{Vo,Vi,Be,Bk}MaxAmsduSize</b> and <b>{Ht,Vht,He}Configuration::{Vo,Vi,Be,Bk}MaxAmpduSize</b> have been removed. Instead, it is necessary to use <b>RegularWifiMac::{VO, VI, BE, BK}_MaxAmsduSize</b> and <b>RegularWifiMac::{VO, VI, BE, BK}_MaxAmpduSize</b>.</li>
<li>A new attribute <b>WifiPhy::PostReceptionErrorModel</b> has been added to force specific packet drops.</li>
<li>A new attribute <b>WifiPhy::PreambleDetectionModel</b> has been added to decide whether PHY preambles are successfully detected.</li>
<li>New attributes <b>QosTxop::AddBaResponseTimeout</b> and <b>QosTxop::FailedAddBaTimeout</b> have been added to set the timeout to wait for an ADDBA response after the ACK to the ADDBA request is received and to set the timeout after a failed BA agreement, respectively.</li>
<li>A new attribute <b>QosTxop::UseExpliciteBarAfterMissedBlockAck</b> has been added to specify whether explicit Block Ack Request should be sent upon missed Block Ack Response.</li>
<li>Added a new trace source <b>EndOfHePreamble</b> in WifiPhy for tracing end of preamble (after training fields) for received 802.11ax packets.</li>
<li>Added a new helper method to SpectrumWifiPhyHelper and YansWifiPhyHelper to set the <b>frame capture model</b>.</li>
<li>Added a new helper method to SpectrumWifiPhyHelper and YansWifiPhyHelper to set the <b>preamble detection model</b>.</li>
<li>Added a new helper method to WifiPhyHelper to disable the preamble detection model.</li>
<li>Added a method to ObjectFactory to check whether a TypeId has been configured on the factory.</li>
<li>Added a new helper method to WifiHelper to set the <b>802.11ax OBSS PD spatial reuse algorithm</b>.</li>
<li>Added the <b>Cobalt queuing discipline</b>.</li>
<li>Added <b>Simulator::GetEventCount ()</b> to return the number of events executed.</li>
<li>Added <b>ShowProgress</b> object to display simulation progress statistics.</li>
<li>Add option to disable explicit Block Ack Request when a Block Ack Response is missed.</li>
<li>Add API to be able to tag a subset of bytes in an ns3::Packet.</li>
<li>New LTE helper API has been added to allow users to configure LTE backhaul links with any link technology, not just point-to-point links.</li>
</ul>
<h2>Changes to existing API:</h2>
<ul>
<li>
Added the possibility of setting the z coordinate for many position-allocation classes: <b>GridPositionAllocator, RandomRectanglePositionAllocator, RandomDiscPositionAllocator, UniformDiscPositionAllocator</b>.
</li>
<li>
The WifiPhy attribute <b>CcaMode1Threshold</b> has been renamed to <b>CcaEdThreshold</b>,
and the WifiPhy attribute <b>EnergyDetectionThreshold</b> has been replaced by a new attribute called <b>RxSensitivity</b>.
</li>
<li>
It is now possible to know the size of the SpectrumValue underlying std::vector, as well as
accessing read-only every element of it.
</li>
<li>
The <b>GetClosestSide</b> method of the Rectangle class returns the correct closest side also for positions outside the rectangle.
</li>
<li> The trace sources <b>BackoffTrace</b> and <b>CwTrace</b> were moved from class QosTxop to base class Txop, allowing these values to be traced for DCF operation. In addition, the trace signature for BackoffTrace was changed from TracedValue to TracedCallback (callback taking one argument instead of two). Most users of CwTrace for QosTxop configurations will not need to change existing programs, but users of BackoffTrace will need to adjust the callback signature to match.
</li>
<li> New trace sources, namely <b>DrbCreated, Srb1Created and DrbCreated</b> have beed implemented in LteEnbRrc and LteUeRrc classes repectively. These new traces are used to improve the connection of the RLC and PDCP stats in the RadioBearerStatsConnector API.
</li>
<li> <b>TraceFadingLossModel</b> has been moved from lte to spectrum module.
</li>
</ul>
<h2>Changes to build system:</h2>
<ul>
<li><b>ns-3 now only supports Python 3</b>. Use of Python 2 can be forced using the --with-python option provided to './waf configure', and may still work for many cases, but is no longer supported. Waf does not default to Python 3 but the ns-3 wscript will default the build to Python 3.
</li>
<li>Waf upgraded from 2.0.9 to 2.0.18.
</li>
<li> Options to run a program through Waf without invoking a project rebuild have been added. The command './waf --run-no-build <program-name>' parallels the behavior of './waf --run <program-name>' and, likewise, the command './waf --pyrun-no-build' parallels the behavior of './waf --pyrun <program-name>'.
</li>
</ul>
<h2>Changed behavior:</h2>
<ul>
<li>The wifi ADDBA handshake process is now protected with the use of two timeouts who makes sure we do not end up in a blocked situation. If the handshake process is not established, packets that are in the queue are sent as normal MPDUs. Once handshake is successfully established, A-MPDUs can be transmitted.</li>
<li> In the wifi module, the default value of the <b>Margin</b> attribute in SimpleFrameCaptureModel was changed from 10 to 5 dB.</li>
<li> A <b>ThresholdPreambleDetectionModel</b> is added by default to the WifiPhy. Using default values, this model will discard frames that fall below either -82 dBm RSSI or below 4 dB SNR. Users may notice that weak wifi signals that were successfully received based on the error model alone (in previous ns-3 releases) are no longer received. Previous behavior can be obtained by lowering both threshold values or by removing the preamble detection model (via WifiPhyHelper::DisablePreambleDetectionModel()).</li>
<li>The PHY model for Wi-Fi has been extended to handle reception of L-SIG and reception of non-legacy header differently.</li>
<li>LTE/EPC model has been enhanced to allow the simulation user to test more realistic topologies related to the core network:</li>
<ul>
<li>SGW, PGW and MME are full nodes.</li>
<li>There are P2P links between core network nodes.</li>
<li>New S5 interface between SGW and PGW nodes based on GTPv2-C protocol.</li>
<li>Allow simulations with multiple SGWs and PGWs.</li>
</ul>
</li>
<li>LTE eNB RRC is extended to support:</li>
<ul>
<li>S1 signalling with the core network is initiated after the RRC connection establishment procedure is finished.</li>
<li>New ATTACH_REQUEST state to wait for finalization of the S1 signalling with the core network.</li>
<li>New InitialContextSetupRequest primitive of the S1 SAP that is received by the eNB RRC when the S1 signalling from the core network is finished.</li>
</ul>
</li>
<li> A new buffer has been introduced in the LteEnbRrc class. This buffer will be used by a target eNB during handover to buffer the packets comming from a source eNB on X2 inteface. The target eNB will buffer this data until it receives RRC Connection Reconfiguration Complete from a UE.
</li>
<li> The default qdisc installed on single-queue devices (such as PointToPoint, Csma and Simple) is now <b>FqCoDel</b> (instead of PfifoFast). On multi-queue devices (such as Wifi), the default root qdisc is now <b>Mq</b> with as many FqCoDel child qdiscs as the number of device queues. The new defaults are motivated by the willingness to align with the behavior of major Linux distributions and by the need to preserve the effectiveness of Wifi EDCA Functions in differentiating Access Categories (see issue #35).</li>
<li>LTE RLC TM mode does not report anymore the layer-to-layer delay, as it misses (by standard) an header to which attach the timestamp tag. Users can switch to the PDCP layer delay measurements, which must be the same.</li>
<li> Token Bank Fair Queue Scheduler (ns3::FdTbfqFfMacScheduler) will not anymore schedule a UE, which does not have any RBG left after removng the RBG from its allocation map if the computed TB size is greater than the "budget" computed in the scheduler.
</li>
<li> LTE module now supports the <b>Radio Link Failure (RLF)</b> functionality. This implementation introduced following key behavioral changes:
<ul>
<li> The UE RRC state will not remain in "CONNECTED_NORMALLY" state if the DL control channel SINR is below a set threshold.</li>
<li> The LTE RRC protocol APIs of UE i.e., LteUeRrcProtocolIdeal, LteUeRrcProtocolReal have been extended to send an ideal (i.e., using SAPs instead to transmitting over the air) UE context remove request to the eNB. Similarly, the eNB RRC protocol APIs, i.e, LteEnbRrcProtocolIdeal and LteEnbRrcProtocolReal have been extended to receive this ideal UE context remove request.</li>
<li> The UE will not synchronize to a cell whose RSRP is less than -140 dBm.</li>
<li> The non-contention based preambles during a handover are re-assigning to an UE only if it has not been assign to another UE (An UE can be using the preamble even after the expiryTime duration).</li>
<li> The RachConfigCommon structure in LteRrcSap API has been extended to include "TxFailParam". This new field would enable an eNB to indicate how many times T300 timer can expire at the UE. Upon reaching this count, the UE aborts the connection establishment, and performs the cell selection again. See TS 36.331 5.3.3.6. </li>
<li> The timer T300 in LteUeRrc class is now bounded by the standard min and max values defined in 3GPP TS 36.331.</li>
</ul>
</li>
</ul>
<hr>
<h1>Changes from ns-3.28 to ns-3.29</h1>
<h2>New API:</h2>
<ul>
<li> CommandLine can now handle non-option (positional) arguments. </li>
<li> Added CommandLine::Parse (const std::vector<std::string>> args) </li>
<li> NS_LOG_FUNCTION can now log the contents of vectors </li>
<li> A new position allocator has been added to the buildings module, allowing
nodes to be placed outside of buildings defined in the scenario.</li>
<li> The Hash() method has been added to the QueueDiscItem class to compute the
hash of various fields of the packet header (depending on the packet type).</li>
<li> Added a priority queue disc (PrioQueueDisc).</li>
<li> Added 3GPP HTTP model
<li> Added TCP PRR as recovery algorithm
<li> Added a new trace source in StaWifiMac for tracing beacon arrivals</li>
<li> Added a new helper method to ApplicationContainer to start applications with some jitter around the start time</li>
<li> (network) Add a method to check whether a node with a given ID is within a NodeContainer.</li>
</ul>
<h2>Changes to existing API:</h2>
<ul>
<li>TrafficControlHelper::Install now only includes root queue discs in the returned
QueueDiscContainer.</li>
<li>Recovery algorithms are now in a different class, instead of being tied to TcpSocketBase.
Take a look to TcpRecoveryOps for more information.</li>
<li>The Mode, MaxPackets and MaxBytes attributes of the Queue class, that had been deprecated in favor of the MaxSize attribute in ns-3.28, have now been removed and cannot be used anymore. Likewise, the methods to get/set the old attributes have been removed as well. Commands such as:
<pre>
Config::SetDefault ("ns3::QueueBase::MaxPackets", UintegerValue (4));
</pre>
should now be written as:
<pre>
Config::SetDefault ("ns3::QueueBase::MaxSize", QueueSizeValue (QueueSize (QueueSizeUnit::PACKETS, 4)));
</pre>
or with a string value with 'b' (bytes) or 'p' (packets) suffix, such as:
<pre>
Config::SetDefault ("ns3::QueueBase::MaxSize", StringValue ("4p"));
</pre>
</li>
<li>The Limit attribute of the PfifoFastQueueDisc class, that had been deprecated in favor of the MaxSize attribute in ns-3.28, has now been removed and cannot be used anymore. Likewise, the methods to get/set the old Limit attribute have been removed as well. The GetMaxSize/SetMaxSize methods of the base QueueDisc class must be used instead.</li>
<li>The Mode, MaxPackets and MaxBytes attributes of the CoDelQueueDisc class, that had been deprecated in favor of the MaxSize attribute in ns-3.28, have now been removed and cannot be used anymore. Likewise, the methods to get/set the old attributes have been removed as well. The GetMaxSize/SetMaxSize methods of the base QueueDisc class must be used instead.</li>
<li>The PacketLimit attribute of the FqCoDelQueueDisc class, that had been deprecated in favor of the MaxSize attribute in ns-3.28, has now been removed and cannot be used anymore. Likewise, the methods to get/set the old PacketLimit attribute have been removed as well. The GetMaxSize/SetMaxSize methods of the base QueueDisc class must be used instead.</li>
<li>The Mode and QueueLimit attributes of the PieQueueDisc class, that had been deprecated in favor of the MaxSize attribute in ns-3.28, have now been removed and cannot be used anymore. Likewise, the methods to get/set the old attributes have been removed as well. The GetMaxSize/SetMaxSize methods of the base QueueDisc class must be used instead.</li>
<li>The Mode and QueueLimit attributes of the RedQueueDisc class, that had been deprecated in favor of the MaxSize attribute in ns-3.28, have now been removed and cannot be used anymore. Likewise, the methods to get/set the old attributes have been removed as well. The GetMaxSize/SetMaxSize methods of the base QueueDisc class must be used instead.</li>
<li> Several traffic generating applications have additional trace sources that export not only the transmitted or received packet but also the source and destination addresses.</li>
<li>The returned type of <b>GetNDevices</b> methods in <b>Channel</b> and subclasses derived from it were changed from uint32_t to std::size_t. Likewise, the input parameter type of <b>GetDevice</b> in <b>Channel</b> and its subclasses were changed from uint32_t to std::size_t.</li>
<li>Wifi classes <b>DcfManager</b>, <b>DcaTxop</b> and <b>EdcaTxopN</b> were renamed to <b>ChannelAccessManager</b>, <b>Txop</b> and <b>QosTxop</b>, respectively.</li>
<li>QueueDisc::DequeuePeeked has been merged into QueueDisc::Dequeue and hence no longer exists.</li>
<li>The QueueDisc base class now provides a default implementation of the DoPeek private method
based on the QueueDisc::PeekDequeue method, which is now no longer available.</li>
<li>The QueueDisc::SojournTime trace source is changed from a TracedValue to a TracedCallback; callbacks that hook this trace must provide one ns3::Time argument, not two.</li>
<li>To avoid the code duplication in SingleModelSpectrumChannel and MultiModelSpectrumChannel classes, the attributes MaxLossDb and PropagationLossModel, and the traces PathLoss and TxSigParams are moved to the base class SpectrumChannel. Similarly, the functions AddPropagationLossModel, AddSpectrumPropagationLossModel, SetPropagationDelayModel and GetSpectrumPropagationLossModel are now defined in SpectrumChannel class. Moreover, the TracedCallback signature of LossTracedCallback has been updated from :
<pre>
typedef void (* LossTracedCallback) (Ptr<SpectrumPhy> txPhy, Ptr<SpectrumPhy> rxPhy, double lossDb);
</pre>
To :
<pre>
typedef void (* LossTracedCallback) (Ptr<const SpectrumPhy> txPhy, Ptr<const SpectrumPhy> rxPhy, double lossDb);
</pre></li>
<li>For the sake of LTE module API consistency the IPV6 related functions AssignUeIpv6Address and GetUeDefaultGatewayAddress6 are now declared in EpcHelper base class. Thus, these functions are now declared as virtual in the child classes, i.e., EmuEpcHelper and PointToPointEpcHelper.</li>
</ul>
<h2>Changes to build system:</h2>
<ul>
<li>Waf upgraded from 1.8.19 to 2.0.9, and ns-3 build scripts aligned to the new API.</li>
<li>The '--no32bit-scan' argument is removed from Waf apiscan; generation of ILP32 bindings is now automated from the LP64 bindings.</li>
<li> When using on newer compilers, new warnings may trigger build failures.
The --disable-werror flag can be passed to Waf at configuration time to turn
off the Werror behavior.</li>
<li> GTK+3 libraries (including PyGObject, GooCanvas2) are needed for the Pyviz visualizer, replacing GTK+2 libraries.</li>
</ul>
<h2>Changed behavior:</h2>
<ul>
<li>FqCoDelQueueDisc now computes the hash of the packet's 5-tuple to determine
the flow the packet belongs to, unless a packet filter has been configured.
The previous behavior is simply obtained by not configuring any packet filter.
Consequently, the FqCoDelIpv{4,6}PacketFilter classes have been removed.</li>
<li> ARP packets now pass through the traffic control layer, as in Linux. </li>
<li> The maximum size UDP packet of the UdpClient application is no longer limited to 1500 bytes.</li>
<li> The default values of the <b>MaxSlrc</b> and <b>FragmentationThreshold</b> attributes in WifiRemoteStationManager were changed from 7 to 4 and from 2346 to 65535, respectively.
</ul>
<hr>
<h1>Changes from ns-3.27 to ns-3.28</h1>
<h2>New API:</h2>
<ul>
<li> When deserializing Packet contents, <b>Header::Deserialize (Buffer::Iterator start)</b> and <b>Trailer::Deserialize (Buffer::Iterator start)</b> can not successfully deserialize variable-length headers and trailers. New variants of these methods that also include an 'end' parameter are now provided.</li>
<li> Ipv[4,6]AddressGenerator can now check if an address is allocated (<b>Ipv[4,6]AddressGenerator::IsAddressAllocated</b>) or a network has some allocated address (<b>Ipv[4,6]AddressGenerator::IsNetworkAllocated</b>).</li>
<li> LTE UEs can now use IPv6 to send and receive traffic.</li>
<li> UAN module now supports an IP stack.</li>
<li> Class <b>TcpSocketBase</b> trace source <i>CongestionWindowInflated</i> shows the values with the in-recovery inflation and the post-recovery deflation.
<li> Added a FIFO queue disc (FifoQueueDisc) and the Token Bucket Filter (TbfQueueDisc).</li>
</ul>
<h2>Changes to existing API:</h2>
<ul>
<li> Class <b>LrWpanMac</b> now supports extended addressing mode. Both <b>McpsDataRequest</b> and <b>PdDataIndication</b> methods will now use extended addressing if <b>McpsDataRequestParams::m_srcAddrMode</b> or <b>McpsDataRequestParams::m_dstAddrMode</b> are set to <b>EXT_ADDR</b>.</li>
<li> Class <b>LteUeNetDevice</b> MAC address is now a 64-bit address and can be set during construction.</li>
<li> Class <b>TcpSocketBase</b> trace source <i>CongestionWindow</i> shows the values without the in-recovery inflation and the post-recovery deflation; the old behavior has been moved to the new trace source <i>CongestionWindowInflated</i>.
<li>The Mode, MaxPackets and MaxBytes attributes of the Queue class have been deprecated in favor of the MaxSize attribute. Old attributes can still be used, but using them will be no longer possible in one of the next releases. The methods to get/set the old attributes will be removed as well.</li>
<li>The attributes of the QueueDisc subclasses that separately determine the mode and the limit of the QueueDisc have been deprecated in favor of the single MaxSize attribute.</li>
<li>The GetQueueSize method of some QueueDisc subclasses (e.g., RED) has been removed and replaced by the GetCurrentSize method of the QueueDisc base class.</li>
</ul>
<h2>Changes to build system:</h2>
<ul>
<li> The C++ standard used during compilation (default std=c++11) can be now be changed via the CXXFLAGS variable.</li>
</ul>
<h2>Changed behavior:</h2>
<ul>
<li>All Wi-Fi management frames are now transmitted using the lowest basic rate.</li>
<li>The Wi-Fi spectrum model now takes into account adjacent channels through OFDM transmit spectrum masks.</li>
<li> The CsmaNetDevice::PhyTxBeginTrace will trace all attempts to transmit, even those that result in drops. Previously, eventual channel drops were excluded from this trace.</l>
<li>The TCP congestion window trace now does not report on window inflation during fast recovery phase because it is no longer internally maintained as an inflated value (a separate trace called CongestionWindowInflated can be used to recover the old trace behavior).</li>
</ul>
<hr>
<h1>Changes from ns-3.26 to ns-3.27</h1>
<h2>New API:</h2>
<ul>
<li>Added <code>Vector{2,3}D.GetLength ()</code>.</li>
<li>Overloaded <code>operator+</code> and <code>operator-</code> for <code>Vector{2,3}D</code>.</li>
<li>Added iterator version of WifiHelper::Install() to install Wi-Fi devices on range of nodes.</li>
<li>Added a new attribute in TcpSocketBase to track the advertised window.</li>
<li>Included the model of <b>TCP Ledbat</b>.</li>
<li>Included the TCP SACK-based loss recovery algorithm outlined in RFC 6675.</li>
<li>Added <b>TCP SACK</b> and the <b>SACK emulation</b>. Added an Attribute to TcpSocketBase class,
called "Sack", to enable or disable the SACK option usage.</li>
<li>In 'src/wifi', several changes were made to enable partial <b>802.11ax</b> High Efficiency (HE) support:
<ul>
<li>A new standard value has been added that enables the new 11ax data rates.</li>
<li>A new 11ax preamble has been added.</li>
<li>A new attribute was added to configure the guard interval duration for High Efficiency (HE) PHY entities. This attribute can be set using the YansWifiPhyHelper.</li>
<li>A new information element has been added: HeCapabilities. This information element is added to the MAC frame header if the node is a HE node. This HeCapabilites information element is used to advertise the HE capabilities of the node to other nodes in the network.</li>
</ul>
</li>
<li> A new class were added for the RRPAA WiFi rate control mechanism.</li>
<li>Included carrier aggregation feature in LTE module</li>
<ul>
<li>LTE model is extended to support carrier aggregation feature according to 3GPP Release 10, for up to 5 component
carriers. </li>
<li>InstallSingleEnbDevice and InstalSingeUeDevice functions of LteHelper are now constructing LteEnbDevice and LteUeDevice
according to CA architecture. Each device, UE and eNodeB contains an instance of component carrier manager, and may
have several component carrier instances.</li>
<li>SAP interfaces are extended to include CA message exchange functionality.</li>
<li>RRC connection procedure is extended to allow RRC connection reconfiguration for the configuration of the secondary carriers.</li>
<li>RRC measurement reporting is extended to allow measurement reporting from the secondary carriers.</li>
<li>LTE traces are extended to include component carrier id.</li>
</ul>
</li>
<li>Function <b>PrintRoutingTable</b> has been extended to add an optional Time::Units
parameter to specify the time units used on the report. The new parameter is
optional and if not specified defaults to the previous behavior (Time::S).
</li>
<li><b>TxopTrace</b>: new trace source exported by EdcaTxopN.</li>
<li>A <b>GetDscpCounts</b> method is added to <b>Ipv4FlowClassifier</b> and <b>Ipv6FlowClassifier</b>
which returns a vector of pairs (dscp,count), each of which indicates how many packets with the
associated dscp value have been classified for a given flow.
</li>
<li>MqQueueDisc, a multi-queue aware queue disc modelled after the mq qdisc in Linux, has been introduced.
</li>
<li>Two new methods, <b>QueueDisc::DropBeforeEnqueue()</b> and <b>QueueDisc::DropAfterDequeue()</b> have
been introduced to replace <b>QueueDisc::Drop()</b>. These new methods require the caller to specify the
reason why a packet was dropped. Correspondingly, two new trace sources ("DropBeforeEnqueue" and
"DropAfterDequeue") have been added to the QueueDisc class, providing both the items that were dropped
and the reason why they were dropped.
</li>
<li>Added <b>QueueDisc::GetStats()</b> which returns detailed statistics about the operations of
a queue disc. Statistics can be accessed through the member variables of the returned object and
by calling the <b>GetNDroppedPackets()</b>, <b>GetNDroppedBytes()</b>, <b>GetNMarkedPackets()</b> and <b>GetNMarkedBytes()</b> methods on the returned object. Such methods return the number of packets/bytes
dropped/marked for the specified reason (passed as argument). Consequently:
<ul>
<li>A number of methods of the QueueDisc class have been removed: <b>GetTotalReceivedPackets()</b>,
<b>GetTotalReceivedBytes()</b>, <b>GetTotalDroppedPackets()</b>, <b>GetTotalDroppedBytes()</b>,
<b>GetTotalRequeuedPackets()</b>, <b>GetTotalRequeuedBytes()</b>.</li>
<li>The <b>Stats</b> struct and the <b>GetStats()</b> method of <b>RedQueueDisc</b> and <b>PieQueueDisc</b> have been removed and replaced by those of the QueueDisc base class.</li>
<li>The <b>GetDropOverLimit</b> and <b>GetDropCount</b> methods of <b>CoDelQueueDisc</b> have been removed.
The values they returned can be obtained by calling, respectively,
GetStats ().GetNDroppedPackets (CoDelQueueDisc::OVERLIMIT_DROP) and
GetStats ().GetNDroppedPackets (CoDelQueueDisc::TARGET_EXCEEDED_DROP). The "DropCount" trace of
<b>CoDelQueueDisc</b> has been removed as well. Packets dropped because the target is exceeded can
be obtained through the new "DropAfterDequeue" trace of the QueueDisc class.</li>
</ul>
</li>
<li> The new <b>QueueDisc::Mark()</b> method has been introduced to allow subclasses to request to mark a packet.
The caller must specify the reason why the packet must be marked. Correspondingly, a new trace source ("Mark")
has been added to the QueueDisc class, providing both the items that were marked and the reason why they
were marked.
</li>
<li>A new trace source, <b>SojournTime</b>, is exported by the QueueDisc base class to provide the
sojourn time of every packet dequeued from a queue disc. This has been made possible by adding a
timestamp to QueueDiscItem objects, which can be set/get through the new <b>GetTimeStamp()</b> and
<b>SetTimeStamp()</b> methods of the QueueDiscItem class. The <b>CoDel</b> queue disc now makes use of such feature of the base class, hence its Sojourn trace source and the CoDelTimestampTag class
have been removed.
</li>
</ul>
<h2>Changes to existing API:</h2>
<ul>
<li><b>ParetoRandomVariable</b> "Mean" attribute has been deprecated,
the "Scale" Attribute have to be used instead.
Changing the Mean attribute has no more an effect on the distribution.
See the documentation for the relationship between Mean, Scale and Shape.
</li>
<li>The default logging timestamp precision has been changed from 6 digits
to 9 digits, with a fixed format to ensure that 9 digits to the right of
the decimal point are always printed. Previously, default C++ iostream
precision and formatting was used.
</li>
<li>Abstract base class <b>WifiChannel</b> has been removed. As a result, a Channel type instead of a WifiChannel type
is now exported by WifiNetDevice.</li>
<li> The <b>GetPacketSize</b> method of <b>QueueItem</b> has been renamed <b>GetSize</b>
</li>
<li> The <b>DequeueAll</b> method of <b>Queue</b> has been renamed <b>Flush</b>
</li>
<li>The attributes <b>WifiPhy::TxAntennas</b> and <b>WifiPhy::RxAntennas</b>,
and the related accessor methods, were replaced by <b>WifiPhy::MaxSupportedTxSpatialStreams</b>
and <b>WifiPhy::MaxSupportedRxSpatialStreams</b>. A new attribute <b>WifiPhy::Antennas</b>
was added to allow users to define the number of physical antennas on the device.
</li>
<li>Sockets do not receive anymore broadcast packets, unless they are bound to an "Any" address (0.0.0.0)
or to a subnet-directed broadcast packet (e.g., x.y.z.0 for a /24 noterok).
As in Linux, the following rules are now enforced:
<ul>
<li> A socket bound to 0.0.0.0 will receive everything.</li>
<li> A socket bound to x.y.z.0/24 will receive subnet-directed broadcast (x.y.z.255) and unicast packets.</li>
<li> A socket bound to x.y.z.w will only receive unicast packets.</li>
</ul>
<b>Previously, a socket bound to an unicast address received also subnet-directed broadcast packets.
This is not anymore possible</b>.
</li>
<li>You can now Bind as many socket as you want to an address/port, provided that they are bound to different NetDevices.
Moreover, BindToNetDevice does not anymore call Bind. In other terms, Bind and BindToNetDevice can be called
in any order.
However, it is suggested to use BindToNetDevice <i>before</i> Bind in order to avoid conflicts.
</li>
</ul>
<h2>Changes to build system:</h2>
<ul>
<li> The API scanning process for Python bindings now relies on CastXML, and only 64-bit scans are presently supported (Linux 64-bit systems). Generation of 32-bit scans is documented in the Python chapter of the ns-3 manual.
</li>
<li> Modules can now be located in the 'contrib/' directory in addition to 'src/'
</li>
<li> Behavior for running Python programs was aligned with that of C++ programs; the list of modules built is no longer printed out.
</li>
</ul>
<h2>Changed behavior:</h2>
<ul>
<li><b>MultiModelSpectrumChannel</b> does not call StartRx for receivers that
operate on subbands orthogonal to transmitter subbands. Models that depend
on receiving signals with zero power spectral density from orthogonal bands
may change their behavior.
See <a href=https://www.nsnam.org/bugzilla/show_bug.cgi?id=2467>bug 2467</a>
for discussion.
</li>
<li><b>Packet Tag objects</b> are no longer constrained to fit within 21
bytes; a maximum size is no longer enforced.
</li>
<li> The default value of the <b>TxGain</b> and <b>RxGain</b> attributes in WifiPhy was changed from 1 dB to 0 dB.
</li>
<li> The reported SNR by WifiPhy::MonitorSnifferRx did not include the RxNoiseFigure, but now does; see <a href=https://www.nsnam.org/bugzilla/show_bug.cgi?id=2783>bug 2783</a> for discussion.
</li>
<li><b>Queue</b> has been redesigned as a template class object, where the type parameter
specifies the type of items to be stored in the queue. As a consequence:
<ul>
<li>Being a subclass of Queue, <b>DropTailQueue</b> is a template class as well.
<li>Network devices such as SimpleNetDevice, PointToPointNetDevice and CsmaNetDevice
use a queue of type Queue<Packet> to store the packets to transmit. The SetQueue
method of their helpers, however, can still be invoked as, e.g.,
SetQueue ("ns3::DropTailQueue") instead of, e.g., SetQueue
("ns3::DropTailQueue<Packet>").</li>
<li>The attributes <b>Mode</b>, <b>MaxPackets</b> and <b>MaxBytes</b> are now
defined by the QueueBase class (which Queue is derived from).</li>
</ul>
</li>
<li>Queue discs that can operate both in packet mode and byte mode (Red, CoDel, Pie) define their own
enum QueueDiscMode instead of using QueueBase::QueueMode.
</li>
<li>The CoDel, PIE and RED queue discs require that the size of the internal queue is the same as
the queue disc limit (previously, it was allowed to be greater than or equal).
</li>
<li> The default value of the <b>EnableBeaconJitter</b> attribute in ApWifiMac was changed from false to true.
</li>
<li> The NormalClose() callback of a TcpSocket object used to fire upon leaving TIME_WAIT state (2*MSL after FINs have been exchanged). It now fires upon entering TIME_WAIT state. Timing of the callback for the other path to state CLOSED (through LAST_ACK) has not been changed.
</li>
</ul>
<hr>
<h1>Changes from ns-3.25 to ns-3.26</h1>
<h2>New API:</h2>
<ul>
<li>A <b>SocketPriorityTag</b> is introduced to carry the packet priority. Such a tag
is added to packets by sockets that support this mechanism (UdpSocketImpl,
TcpSocketBase and PacketSocket). The base class Socket has a new SetPriority
method to set the socket priority. When the IPv4 protocol is used, the
priority is set based on the ToS. See the Socket options section of the
Network model for more information.
</li>
<li>A <b>WifiNetDevice::SelectQueue</b> method has been added to determine the user
priority of an MSDU. This method is called by the traffic control layer before
enqueuing a packet in the queue disc, if a queue disc is installed on
the outgoing device, or passing a packet to the device, otherwise. The
user priority is set to the three most significant bits of the DS field
(TOS field in case of IPv4 and Traffic Class field in case of IPv6). The
packet priority carried by the SocketPriorityTag is set to the user priority.
</li>
<li>The <b>PfifoFastQueueDisc</b> classifies packets into bands based on their priority.
See the pfifo_fast queue disc section of the Traffic Control Layer model
for more information.
</li>
<li>A new class <b>SpectrumWifiPhy</b> has been introduced that makes use of the
Spectrum module. Its functionality and API is currently very similar to that
of the YansWifiPhy, especially because it reuses the same InterferenceHelper
and ErrorModel classes (for this release). Some example programs in the
'examples/wireless/' directory, such as 'wifi-spectrum-per-example.cc',
illustrate how the SpectrumWifiPhy class can be substituted for the default
YansWifiPhy PHY model.
</li>
<li>We have added support for generating traces for the
<a href="https://wilseypa.github.io/desMetrics">DES Metrics</a> project.
These can be enabled by adding <tt>--enable-des-metrics</tt> at configuration;
you must also use <tt>CommandLine</tt> in your script. See the API docs
for class <b>DesMetrics</b> for more details.
</li>
<li> The traffic control module now includes the <b>FQ-CoDel</b> and <b>PIE</b> queue disc
models, and behavior corresponding to Linux <b>Byte Queue Limits (BQL)</b>.
</li>
<li> Several new TCP congestion control variants were introduced, including
<b>TCP Vegas, Scalable, Veno, Illinois, Bic, YeAH, and H-TCP</b>
congestion control algorithms.
</li>
</ul>
<h2>Changes to existing API:</h2>
<ul>
<li><b>SocketAddressTag</b> was a long-standing approach to approximate the POSIX
socket recvfrom behavior (i.e., to know the source address of a packet)
without actually calling RecvFrom. Experience with this revealed that
this option was difficult to use with tunnels (the new tag has to
replace the old one). Moreover, there is no real need
to create a new API when there is a an existing one (i.e., RecvFrom).
As a consequence, SocketAddressTag has been completely removed from ns-3.
Users can use RecvFrom (for UDP), GetPeerName (for TCP), or similar.
</li>
<li><b>InetSockAddress</b> can now store a ToS value, which can be set through its
SetTos method. The Bind and Connect methods of UDP (UdpSocketImpl) and
TCP (TcpSocketBase) sockets set the socket ToS value to the value provided
through the address input parameter (of type InetSockAddress). See the
Socket options section of the Network model for more information.
</li>
<li>The <b>QosTag</b> is removed as it has been superseded by the SocketPriorityTag.</li>
<li>The <b>Ipv4L3Protocol::DefaultTos</b> attribute is removed.</li>
<li>The attributes <b>YansWifiPhy::Frequency, YansWifiPhy::ChannelNumber, and
YansWifiPhy::ChannelWidth</b>, and the related accessor methods, were moved to
base class WifiPhy. YansWifiPhy::GetChannelFrequencyMhz() was deleted.
A new method WifiPhy::DefineChannelNumber () was added to allow users to
define relationships between channel number, standard, frequency, and channel width.
</li>
<li>The class <b>WifiSpectrumValueHelper</b> has been refactored; previously it
was an abstract base class supporting the WifiSpectrumValue5MhzFactory spectrum
model. It now contains various static member methods supporting the creation
of power spectral densities with the granularity of a Wi-Fi OFDM subcarrier
bandwidth. The class <b>WifiSpectrumValue5MhzFactory</b> and its API remain but
it is not subclassed.
</li>
<li>A new Wifi method <b>InterferenceHelper::AddForeignSignal</b> has been introduced to
support use of the SpectrumWifiPhy (so that non-Wi-Fi signals may be handled
as noise power).
</li>
<li>A new Wifi attribute <b>Dcf::TxopLimit</b> has been introduced to add support for 802.11e TXOP.
</li>
</ul>
<h2>Changes to build system:</h2>
<ul>
<li> A new waf build option, <tt>--check-config</tt>, was added to allow users to print the current configuration summary, as appears at the end of ./waf configure. See bug 2459 for discussion.</li>
<li> The <tt>configure</tt> summary is now sorted, to make it easier to check the status of optional features.</li>
</ul>
<h2>Changed behavior:</h2>
This section is for behavioral changes to the models that were not due to a bug fix.
<ul>
<li>The relationship between Wi-Fi channel number, frequency, channel width,
and Wi-Fi standard has been revised (see bug 2412). Previously, ChannelNumber
and Frequency were attributes of class YansWifiPhy, and the frequency was
defined as the start of the band. Now, Frequency has been redefined to be
the center frequency of the channel, and the underlying device relies on
the pair of frequency and channel width to control behavior; the channel
number and Wi-Fi standard are used as attributes to configure frequency
and channel width. The wifi module documentation discusses this change
and the new behavior.
</li>
<li>AODV now honors the TTL in RREQ/RREP and it uses a method
compliant with <a href="http://www.ietf.org/rfc/rfc3561.txt">RFC 3561</a>. The node search radius is increased progressively. This could increase
slightly the node search time, but it also decreases the network
congestion.
</li>
</ul>
<hr>
<h1>Changes from ns-3.24 to ns-3.25</h1>
<h2>New API:</h2>
<ul>
<li> In 'src/internet/test', a new environment is created to test TCP properties.</li>
<li> The 'src/traffic-control' module has been added, with new API for adding and configuring queue discs and packet filters.</li>
<li> Related to traffic control, a new interface has been added to the
NetDevice to provide a queue interface to access device queue state and
register callbacks used for flow control.</li>
<li> In 'src/wifi', a new rate control (MinstrelHT) has been added for
802.11n/ac modes.</li>
<li> In 'src/wifi', a new helper (WifiMacHelper) is added and is a merged helper from all previously existing MAC helpers (NqosWifiMacHelper, QosWifiMacHelper, HtWifiMacHelper and VhtWifiMacHelper).</li>
<li> It is now possible to use RIPv2 in IPv4 network simulations.</li>
</ul>
<h2>Changes to existing API:</h2>
<ul>
<li>TCP-related changes:
<ul>
<li>Classes TcpRfc793, TcpTahoe, and TcpReno were removed.</li>
<li>The 'TcpNewReno' log component was effectively replaced by 'TcpCongestionOps'
<li>TCP Hybla and HighSpeed have been added.</li>
<li>Added the concept of Congestion State Machine inside TcpSocketBase.</li>
<li>Merged Fast Recovery and Fast Retransmit inside TcpSocketBase.</li>
<li>Some member variables have been moved from TcpSocketBase inside TcpSocketState. Attributes are not touched.</li>
<li>Congestion control split from TcpSocketBase as subclass of TcpCongestionOps.</li>
<li>Added Rx and Tx callbacks on TcpSocketBase.</li>
<li>Added BytesInFlight trace source on TcpSocketBase. The trace is updated when the implementation requests the value.</li>
<li>Added attributes about the number of connection and data retransmission attempts.</li>
</ul>
</li>
<li> ns-3 is now capable of serializing SLL (a.k.a. cooked) headers.
This is used in DCE to allow the generation of pcap directly readable by wireshark.
</li>
<li> In the WifiHelper class in the wifi module, Default has been declared deprecated. This is now immediately handled by the constructor of the class.</li>
<li> The API for configuring 802.11n/ac aggregation has been modified to be more user friendly. As any MAC layer attributes, aggregation parameters can now also be configured through WifiMacHelper::SetType. </li>
<li> The class Queue and subclasses derived from it have been changed in two ways:
<ul>
<li>Queues no longer enqueue simple Packets but instead enqueue QueueItem objects, which include Packet but possibly other information such as headers.</li>
<li>The attributes governing the mode of operation (packets or bytes) and the maximum size have been moved to base class Queue.</li>
</ul>
</li>
<li> Users of advanced queues (RED, CoDel) who have been using them directly in the NetDevice will need to adjust to the following changes:
<ul>
<li> RED and CoDel are no longer specializations of the Queue class, but are now specializations of the new QueueDisc class. This means that RED and CoDel can now be installed in the context of the new Traffic Control layer instead of as queues in (some) NetDevices. The reason for such a change is to make the ns-3 stack much more similar to that of real operating systems (Linux has been taken as a reference). Queuing disciplines such as RED and CoDel can now be tested with all the NetDevices, including WifiNetDevices. </li>
<li> NetDevices still use queues to buffer packets. The only subclass of Queue currently available for this purpose is DropTailQueue. If one wants to approximate the old behavior, one needs to set the DropTailQueue MaxPackets attribute to very low values, e.g., 1.</li>
<li> The Traffic Control layer features a mechanism by which packets dropped by the NetDevice are requeued in the queue disc (more precisely: if NetDevice::Send returns false, the packet is requeued), so that they are retransmitted later. This means that the MAC drop traces may include packets that have not been actually lost, because they have been dropped by the device, requeued by the traffic control layer and successfully retransmitted. To get the correct number of packets that have been actually lost, one has to subtract the number of packets requeued from the number of packets dropped as reported by the MAC drop trace. </li>
</ul>
</li>
</ul>
<h2>Changes to build system:</h2>
<ul>
<li> Waf was upgraded to 1.8.19</li>
<li> A new waf build option, --check-profile, was added to allow users to check the currently active build profile. It is discussed in bug 2202 in the tracker.</li>
</ul>
<h2>Changed behavior:</h2>
This section is for behavioral changes to the models that were not due to a bug fix.
<ul>
<li>TCP behavioral changes:
<ul>
<li>TCP closes connection after a number of failed segment retries,
rather than trying indefinitely. The maximum number of retries, for both SYN
attempts and data attempts, is controlled by attributes.</li>
<li>Congestion algorithms not compliant with Fast Retransmit
and Fast Recovery (TCP 793, Reno, Tahoe) have been removed.</li>
</ul>
</li>
<li> 802.11n/ac MPDU aggregation is now enabled by default for both AC_BE and AC_VI.</li>
<li> The introduction of the traffic control layer leads to some additional buffering by default in the stack; when a device queue fills up, additional packets become enqueued at the traffic control layer.</li>
</ul>
<hr>
<h1>Changes from ns-3.23 to ns-3.24</h1>
<h2>New API:</h2>
<ul>
<li>In 'src/wifi', several changes were made to enable partial 802.11ac support:
<ul>
<li>A new helper (VhtWifiMacHelper) was added to set up a Very high throughput (VHT) MAC entity.</li>
<li>A new standard value has been added that enables the new 11ac data rates.</li>
<li>A new 11ac preamble has been added.</li>
<li>A new information element has been added: VhtCapabilities. This information element is added to the MAC frame header if the node is a VHT node. This VhtCapabilites information element is used to advertise the VHT capabilities of the node to other nodes in the network.</li>
</ul>
</li>
<li>The ArpCache API was extended to allow the manual removal of ArpCache entries and the addition of permanent (static) entries for IPv4.
</li>
<li> The SimpleChannel in the 'network' module now allows per-NetDevice blacklists, in order to do hidden terminal testcases.
</li>
</ul>
<h2>Changes to existing API:</h2>
<ul>
<li> The signatures on several TcpHeader methods were changed to take const arguments.</li>
<li> class TcpL4Protocol replaces Send() methods with SendPacket(), and adds new methods to AddSocket() and RemoveSocket() from a node. Also, a new PacketReceived() method was introduced to get the TCP header of an incoming packet and check its checksum.</li>
<li> The CongestionWindow and SlowStartThreshold trace sources have been moved from the TCP subclasses such as NewReno, Reno, Tahoe, and Westwood to the TcpSocketBase class.</li>
<li> The WifiMode object has been refactored:
<ul>
<li>11n data rates are now renamed according to their MCS value. E.g. OfdmRate65MbpsBW20MHz has been renamed into HtMcs7. 11ac data rates have been defined according to this new renaming.</li>
<li>HtWifiMacHelper and VhtWifiMacHelper provide a helper to convert a MCS value into a data rate value.</li>
<li>The channel width is no longer tied to the wifimode. It is now included in the TXVECTOR.</li>
<li>The physical bitrate is no longer tied to the wifimode. It is computed based on the selected wifimode and on the TXVECTOR parameters (channel width, guard interval and number of spatial streams).</li>
</ul>
</li>
</ul>
<h2>Changes to build system:</h2>
<ul>
<li> Waf was upgraded to 1.8.12</li>
<li> Waf scripts and test.py test runner program were made compatible with Python 3</li>
</ul>
<h2>Changed behavior:</h2>
This section is for behavioral changes to the models that were not due to a bug fix.
<ul>
</ul>
<hr>
<h1>Changes from ns-3.22 to ns-3.23</h1>
<h2>New API:</h2>
<ul>
<li> The mobility module includes a GeographicPositions class used to
convert geographic to cartesian coordinates, and to generate randomly
distributed geographic coordinates.
</li>
<li> The spectrum module includes new TvSpectrumTransmitter classes and helpers to create television transmitter(s) that transmit PSD spectrums customized by attributes such as modulation type, power, antenna type, channel frequency, etc.
</li>
</ul>
<h2>Changes to existing API:</h2>
<ul>
<li> In LteSpectrumPhy, LtePhyTxEndCallback and the corresponding methods have been removed, since they were unused.
</li>
<li> In the DataRate class in the network module, CalculateTxTime has been declared deprecated. CalculateBytesTxTime and CalculateBitsTxTime are to be used instead. The return value is a Time, instead of a double.
</li>
<li> In the Wi-Fi InterferenceHelper, the interference event now takes the WifiTxVector as an input parameter, instead of the WifiMode. A similar change was made to the WifiPhy::RxOkCallback signature.
</li>
</ul>
<h2>Changes to build system:</h2>
<ul>
<li> None </li>
</ul>
<h2>Changed behavior:</h2>
This section is for behavioral changes to the models that were not due to a bug fix.
<ul>
<li> In Wi-Fi, HT stations (802.11n) now support two-level aggregation. The InterferenceHelper now distinguishes between the PLCP and regular payload reception, for higher fidelity modeling. ACKs are now sent using legacy rates and preambles. Access points now establish BSSBasicRateSet for control frame transmissions. PLCP header and PLCP payload reception have been decoupled to improve PHY layer modeling accuracy. RTS/CTS with A-MPDU is now fully supported.
</li>
<li> The mesh module was made more compliant to the IEEE 802.11s-2012 standard and packet traces are now parseable by Wireshark.
</li>
</ul>
<hr>
<h1>Changes from ns-3.21 to ns-3.22</h1>
<h2>New API:</h2>
<ul>
<li> New classes were added for the PARF and APARF WiFi power and rate control mechanisms.
</li>
<li> Support for WiFi 802.11n MPDU aggregation has been added.
</li>
<li> Additional support for modeling of vehicular WiFi networks has been added, including the channel-access coordination feature of IEEE 1609.4. In addition, a Basic Safety Message (BSM) packet generator and related statistics-gathering classes have been added to the wave module.
</li>
<li> A complete LTE release bearer procedure is now implemented which can be invoked by calling the new helper method LteHelper::DeActivateDedicatedEpsBearer ().
</li>
<li> It is now possible to print the Neighbor Cache (ARP and NDISC) by using
the RoutingProtocolHelper
</li>
<li> A TimeProbe class has been added to the data collection framework in
the stats module, enabling TracedValues emitting values of type
ns3::Time to be handled by the framework.
</li>
<li> A new attribute 'ClockGranularity' was added to the TcpSocketBase class,
to control modeling of RTO calculation.
</li>
</ul>
<h2>Changes to existing API:</h2>
<ul>
<li> Several deprecated classes and class methods were removed, including EmuNetDevice, RandomVariable and derived classes, Packet::PeekData(), Ipv6AddressHelper::NewNetwork(Ipv6Address, Ipv6Prefix), Ipv6InterfaceContainer::SetRouter(), Ipv4Route::GetOutputTtl(), TestCase::AddTestCase(TestCase*), and TestCase::GetErrorStatus().
</li>
<li> Print methods involving routing tables and neighbor caches, in classes Ipv4RoutingHelper and Ipv6RoutingHelper, were converted to static methods.
</li>
<li>PointerValue attribute types in class UanChannel (NoiseModel), UanPhyGen (PerModel and SinrModel), UanPhyDual (PerModelPhy1, PerModelPhy2, SinrModelPhy1, and SinrModelPhy2), and SimpleNetDevice (TxQueue), were changed from PointerValue type to StringValue type, making them configurable via the Config subsystem.
</li>
<li> WifiPhy::CalculateTxDuration() and WifiPhy::GetPayloadDurationMicroSeconds () now take an additional frequency parameter.
</li>
<li> The attribute 'Recievers' in class YansWifiPhy was misspelled, so
this has been corrected to 'Receivers'.
</li>
<li> We have now documented the callback function signatures
for all TracedSources, using an extra (fourth) argument to
TypeId::AddTraceSource to pass the fully-qualified name
of the signature typedef. To ensure that future TraceSources
are similarly documented, the three argument version of
AddTraceSource has been deprecated.
</li>
<li> The "MinRTO" attribute of the RttEstimator class was moved to the TcpSocketBase class. The "Gain" attribute of the RttMeanDeviation class was replaced
by new "Alpha" and "Beta" attributes.
</li>
<li> Attributes of the TcpTxBuffer and TcpRxBuffer class are now accessible through the TcpSocketBase class.
</li>
<li> The LrWpanHelper class has a new constructor allowing users to configure a MultiModelSpectrumChannel as an option, and also provides Set/Get API to allow users to access the underlying channel object.
</li>
</ul>
<h2>Changes to build system:</h2>
<ul>
<li> waf was upgraded to version 1.7.16
</li>
</ul>
<h2>Changed behavior:</h2>
This section is for behavioral changes to the models that were not due to a bug fix.
<ul>
<li> The default value of the `Speed` attribute of ConstantSpeedPropagationDelayModel was changed from 300,000,000 m/s to 299,792,458 m/s (speed of light in a vacuum), causing propagation delays using this model to vary slightly.
</li>
<li> The LrWpanHelper object was previously instantiating only a LogDistancePropagationLossModel on a SingleModelSpectrumChannel, but no PropagationDelayModel. The constructor now adds by default a ConstantSpeedPropagationDelayModel.
</li>
<li> The Nix-vector routing implementation now uses a lazy flush mechanism,
which dramatically speeds up the creation of large topologies.
</li>
</ul>
<hr>