3 ns-3 as a SimGrid model
4 #######################
6 You can use the well-known `ns-3 packet-level network simulator
7 <http://www.nsnam.org>`_ as a SimGrid model, for example to investigate the
8 validity of your simulation. Just install ns-3 and recompile SimGrid
11 Compiling the ns-3/SimGrid binding
12 **********************************
17 SimGrid requires ns-3 version 3.26 or higher, and you probably want the most
18 recent version of both SimGrid and ns-3. While the Debian package of SimGrid
19 don't have the ns-3 bindings activated, you can still use the packaged version
20 of ns-3 by grabbing the ``libns3-dev ns3`` packages. Alternatively, you can
21 install ns-3 from scratch as follows:
26 wget http://www.nsnam.org/release/ns-allinone-3.29.tar.bz2
27 tar -xf ns-allinone-3.29.tar.bz2
28 cd ns-allinone-3.29/ns-3.29/
29 # Configure, build and install
30 ./waf configure --prefix="/opt/ns3" # or give another path if you prefer
34 For more information, please refer to the ns-3 documentation
35 (`official website <http://www.nsnam.org>`_).
37 Enabling ns-3 in SimGrid
38 ========================
40 SimGrid must be recompiled with the ``enable_ns3`` option activated in cmake.
41 Optionally, use ``NS3_HINT`` to hint cmake about where to find ns-3.
45 cmake . -Denable_ns3=ON -DNS3_HINT=/opt/ns3 # or change the path if needed
47 By the end of the configuration, cmake reports whether ns-3 was found,
48 and this information is also available in ``include/simgrid/config.h``
49 If your local copy defines the variable ``SIMGRID_HAVE_NS3`` to 1, then ns-3
50 was correctly detected. Otherwise, explore ``CMakeFiles/CMakeOutput.log`` and
51 ``CMakeFiles/CMakeError.log`` to diagnose the problem.
53 Test your installation after compilation as follows:
62 If you use a version of ns-3 that is not known to SimGrid yet, edit
63 ``tools/cmake/Modules/FindNS3.cmake`` in your SimGrid tree, according to the
64 comments on top of this file. Conversely, if something goes wrong with an old
65 version of either SimGrid or ns-3, try upgrading everything.
69 Using ns-3 from SimGrid
70 ***********************
72 The SimGrid/ns-3 binding only contains features that are common to both
73 systems. Also, the platform built in ns-3 from the
74 SimGrid description is very basic.
76 Platform files compatibility
77 ============================
79 Any route longer than one will be ignored when using ns-3. They are
80 harmless, but you still need to connect your hosts using one-hop routes.
81 The best solution is to add routers to split your route. Here is an
82 example of invalid platform:
86 <?xml version='1.0'?><!DOCTYPE platform SYSTEM "http://simgrid.gforge.inria.fr/simgrid/simgrid.dtd">
87 <platform version="4.1">
88 <AS id="AS0" routing="Floyd">
90 <host id="alice" speed="1Gf" />
91 <host id="bob" speed="1Gf" />
93 <link id="l1" bandwidth="1Mbps" latency="5ms" />
94 <link id="l2" bandwidth="1Mbps" latency="5ms" />
96 <route src="alice" dst="bob">
97 <link_ctn id="l1"/> <!-- !!!! INVALID WITH ns-3 !!!! -->
98 <link_ctn id="l2"/> <!-- !!!! length=2 IS TOO MUCH !!!! -->
103 This can be reformulated as follows to make it usable with the ns-3 binding.
104 There is no direct connection from alice to bob, but that's OK because
105 ns-3 automatically routes from point to point.
107 .. code-block:: shell
109 <?xml version='1.0'?><!DOCTYPE platform SYSTEM "http://simgrid.gforge.inria.fr/simgrid/simgrid.dtd">
110 <platform version="4.1">
111 <AS id="AS0" routing="Floyd">
113 <host id="alice" speed="1Gf"/>
114 <host id="bob" speed="1Gf"/>
116 <router id="r1"/> <!-- routers are compute-less hosts -->
118 <link id="l1" bandwidth="1Mbps" latency="5ms"/>
119 <link id="l2" bandwidth="1Mbps" latency="5ms"/>
121 <route src="alice" dst="r1">
125 <route src="r1" dst="bob">
131 Once your platform is OK, just change the :ref:`network/model
132 <options_model_select>`_ configuration option to "ns-3" as follows. The rest
135 .. code-block:: shell
137 ./network-ns3 --cfg=network/model:ns-3 (other parameters)
139 Many other files from the ``examples/platform directory`` are usable with the
142 Build a wifi-compatible platform
143 ===================================
145 We describe here a simple platform allowing ns3 wifi communication
146 between two simgrid hosts.
148 First, here are the mandatory information necessary to create a
151 .. code-block:: shell
153 <?xml version='1.0'?><!DOCTYPE platform SYSTEM "http://simgrid.gforge.inria.fr/simgrid/simgrid.dtd">
154 <platform version="4.1">
155 <AS id="AS0" routing="Floyd">
157 Then, we create our access point and station hosts:
159 .. code-block:: shell
161 <host id="alice" speed="1Gf"/>
162 <host id="bob" speed="1Gf"/>
164 We must specify that alice will be our access point. To do that we
165 simply add the property ``wifi_link`` to the host ``alice``:
167 .. code-block:: shell
169 <host id="alice" speed="1Gf">
170 <prop id="wifi_link" value="net0"/>
173 <host id="bob" speed="1Gf"/>
175 The value ``net0`` of this property defines the name of the wifi network
176 generated. To generate this wifi network we create a wifi link:
178 .. code-block:: shell``
180 <link id="net0" bandwidth="0" latency="0" sharing_policy="WIFI"/>
182 The important information here are:
183 * The id of the link, ``net0``, must match the network name defined by the property ``wifi_link`` of the access point node
184 * The sharing policy must be set to ``WIFI``
186 Note: bandwidth and latency are mandatory by simgrid to create a link but are NOT used to create a wifi network. Instead the
187 wifi network capabilities are defined by its MCS, NSS and distance from access point to station. Those properties are described in section :ref:`Optional access point node properties <optional_prop>`_
189 To connect the station node to the access point node, we
190 create a route between the hosts:
192 .. code-block:: shell
194 <route src="alice" dst="bob">
195 <link_ctn id="net0" />
198 Finally, we end the xml file with the missing closing tags:
200 .. code-block:: shell
207 Optional access point node properties
208 --------------------------------------
210 The MCS (`Modulation and Coding Scheme <https://en.wikipedia.org/wiki/Link_adaptation>`_) can be set with the property ``wifi_mcs``:
212 .. code-block:: shell
214 <host id="alice" speed="1Gf">
215 <prop id="wifi_link" value="net0"/>
216 <prop id="wifi_mcs" value="5"/>
219 Its default value is 3.
221 The NSS (Number of Spatial Streams, also known as the `number of antennas <https://en.wikipedia.org/wiki/IEEE_802.11n-2009#Number_of_antennas>`_) can be set with the property ``wifi_nss``:
223 .. code-block:: shell
225 <host id="alice" speed="1Gf">
226 <prop id="wifi_link" value="net0"/>
227 <prop id="wifi_nss" value="2"/>
230 Its default value is 1.
232 Note: not all value of MCS and NSS are valid nor compatible. Check `802.11n standard <https://en.wikipedia.org/wiki/IEEE_802.11n-2009#Data_rates>`_ for more information.
234 Optional station node properties
235 ---------------------------------
237 The distance in meter at which the station is placed from the access point can
238 be set with the property ``wifi_distance``.
240 .. code-block:: shell
242 <host id="alice" speed="100.0Mf,50.0Mf,20.0Mf" pstate="0">
243 <prop id="wifi_distance" value="30" />
246 Its default value is 10.
251 A ns-3 platform is automatically created from the provided SimGrid
252 platform. However, there are some known caveats:
254 * The default values (e.g., TCP parameters) are the ns-3 default values.
255 * ns-3 networks are routed using the shortest path algorithm, using
256 ``ns3::Ipv4GlobalRoutingHelper::PopulateRoutingTables``.
258 Our goal is to keep the ns-3 plugin of SimGrid as easy (and hopefully readable)
259 as possible. If the current state does not fit your needs, you should modify
260 this plugin, and/or create your own plugin from the existing one. If you come up
261 with interesting improvements, please contribute them back.
266 If your simulation hangs in a communication, this is probably because one host
267 is sending data that is not routable in your platform. Make sure that you only
268 use routes of length 1, and that any host is connected to the platform.
269 Arguably, SimGrid could detect this situation and report it, but unfortunately,
270 this is still to be done.