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 (see the `ns-3 documentation <http://www.nsnam.org>`_).
23 Enabling ns-3 in SimGrid
24 ========================
26 SimGrid must be recompiled with the ``enable_ns3`` option activated in cmake.
27 Optionally, use ``NS3_HINT`` to tell cmake where ns3 is installed on
32 cmake . -Denable_ns3=ON -DNS3_HINT=/opt/ns3 # or change the path if needed
34 By the end of the configuration, cmake reports whether ns-3 was found,
35 and this information is also available in ``include/simgrid/config.h``
36 If your local copy defines the variable ``SIMGRID_HAVE_NS3`` to 1, then ns-3
37 was correctly detected. Otherwise, explore ``CMakeFiles/CMakeOutput.log`` and
38 ``CMakeFiles/CMakeError.log`` to diagnose the problem.
40 Test your installation after compilation as follows:
49 If you use a version of ns-3 that is not known to SimGrid yet, edit
50 ``tools/cmake/Modules/FindNS3.cmake`` in your SimGrid tree, according to the
51 comments on top of this file. Conversely, if something goes wrong with an old
52 version of either SimGrid or ns-3, try upgrading everything.
56 Using ns-3 from SimGrid
57 ***********************
59 The SimGrid/ns-3 binding only contains features that are common to
60 both systems. Not all ns-3 models are available (only the TCP and wifi
61 ones are), while not all SimGrid platform file can be used with ns-3
62 (routes must be of length 1). Also, the platform built in ns-3 from
63 the SimGrid description is very basic.
65 Platform files compatibility
66 ============================
68 Any route longer than one will be ignored when using ns-3. They are
69 harmless, but you still need to connect your hosts using one-hop routes.
70 The best solution is to add routers to split your route. Here is an
71 example of an invalid platform:
76 <!DOCTYPE platform SYSTEM "https://simgrid.org/simgrid.dtd">
77 <platform version="4.1">
78 <zone id="zone0" routing="Floyd">
79 <host id="alice" speed="1Gf" />
80 <host id="bob" speed="1Gf" />
82 <link id="l1" bandwidth="1Mbps" latency="5ms" />
83 <link id="l2" bandwidth="1Mbps" latency="5ms" />
85 <route src="alice" dst="bob">
86 <link_ctn id="l1"/> <!-- !!!! INVALID WITH ns-3 !!!! -->
87 <link_ctn id="l2"/> <!-- !!!! length=2 IS TOO MUCH !!!! -->
92 This can be reformulated as follows to make it usable with the ns-3 binding.
93 There is no direct connection from alice to bob, but that's OK because
94 ns-3 automatically routes from point to point.
99 <!DOCTYPE platform SYSTEM "https://simgrid.org/simgrid.dtd">
100 <platform version="4.1">
101 <zone id="zone0" routing="Full">
102 <host id="alice" speed="1Gf" />
103 <host id="bob" speed="1Gf" />
105 <router id="r1" /> <!-- routers are compute-less hosts -->
107 <link id="l1" bandwidth="1Mbps" latency="5ms"/>
108 <link id="l2" bandwidth="1Mbps" latency="5ms"/>
110 <route src="alice" dst="r1">
114 <route src="r1" dst="bob">
120 Once your platform is OK, just change the :ref:`network/model
121 <options_model_select>`_ configuration option to "ns-3" as follows. The rest
124 .. code-block:: shell
126 ./network-ns3 --cfg=network/model:ns-3 (other parameters)
128 Many other files from the ``examples/platform directory`` are usable with the
129 ns-3 model, such as `examples/platforms/dogbone.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/dogbone.xml>`_.
130 Check the file `examples/s4u/network-ns3/network-ns3.tesh <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/network-ns3/network-ns3.tesh>`_
131 to see which ones are used in our regression tests.
133 Build a wifi-compatible platform
134 ===================================
136 We describe here a simple platform allowing ns3 wifi communication
137 between two SimGrid hosts.
139 First, here are the mandatory information necessary to create a
142 .. code-block:: shell
144 <?xml version='1.0'?>
145 <!DOCTYPE platform SYSTEM "http://simgrid.org/simgrid.dtd">
146 <platform version="4.1">
147 <zone id="zone" routing="Floyd">
149 Then, we create our access point and station hosts:
151 .. code-block:: shell
153 <host id="alice" speed="1Gf"/>
154 <host id="bob" speed="1Gf"/>
156 We must specify that alice will be our access point. To do that we
157 simply add the property ``wifi_link`` to the host ``alice``:
159 .. code-block:: shell
161 <host id="alice" speed="1Gf">
162 <prop id="wifi_link" value="net0"/>
165 <host id="bob" speed="1Gf"/>
167 The value ``net0`` of this property defines the name of the wifi network
168 generated. To generate this wifi network we create a wifi link:
170 .. code-block:: shell
172 <link id="net0" bandwidth="0" latency="0" sharing_policy="WIFI"/>
174 The important information here are:
175 * The id of the link, ``net0``, must match the network name defined by the property ``wifi_link`` of the access point node
176 * The sharing policy must be set to ``WIFI``
178 Note: bandwidth and latency are mandatory by simgrid to create a link but are NOT used to create a wifi network. Instead the
179 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>`_
181 To connect the station node to the access point node, we
182 create a route between the hosts:
184 .. code-block:: shell
186 <route src="alice" dst="bob">
187 <link_ctn id="net0" />
190 Finally, we end the xml file with the missing closing tags:
192 .. code-block:: shell
199 Optional access point node properties
200 --------------------------------------
202 The MCS (`Modulation and Coding Scheme <https://en.wikipedia.org/wiki/Link_adaptation>`_) can be set with the property ``wifi_mcs``:
204 .. code-block:: shell
206 <host id="alice" speed="1Gf">
207 <prop id="wifi_link" value="net0"/>
208 <prop id="wifi_mcs" value="5"/>
211 Its default value is 3.
213 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``:
215 .. code-block:: shell
217 <host id="alice" speed="1Gf">
218 <prop id="wifi_link" value="net0"/>
219 <prop id="wifi_nss" value="2"/>
222 Its default value is 1.
224 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.
226 Optional station node properties
227 ---------------------------------
229 The distance in meter at which the station is placed from the access point can
230 be set with the property ``wifi_distance``.
232 .. code-block:: shell
234 <host id="alice" speed="100.0Mf,50.0Mf,20.0Mf" pstate="0">
235 <prop id="wifi_distance" value="30" />
238 Its default value is 10.
243 A ns-3 platform is automatically created from the provided SimGrid
244 platform. However, there are some known caveats:
246 * The default values (e.g., TCP parameters) are the ns-3 default values.
247 * ns-3 networks are routed using the shortest path algorithm, using
248 ``ns3::Ipv4GlobalRoutingHelper::PopulateRoutingTables``.
249 * End hosts cannot have more than one interface card. So, your
250 SimGrid hosts should be connected to the platform through only
251 one link. Otherwise, your SimGrid host will be considered as a
252 router (FIXME: is it still true?).
254 Our goal is to keep the ns-3 plugin of SimGrid as easy (and hopefully readable)
255 as possible. If the current state does not fit your needs, you should modify
256 this plugin, and/or create your own plugin from the existing one. If you come up
257 with interesting improvements, please contribute them back.
262 If your simulation hangs in a communication, this is probably because one host
263 is sending data that is not routable in your platform. Make sure that you only
264 use routes of length 1, and that any host is connected to the platform.
265 Arguably, SimGrid could detect this situation and report it, but unfortunately,
266 this is still to be done.