validity of your simulation. Just install ns-3 and recompile SimGrid
accordingly.
+The SimGrid/ns-3 binding only contains features that are common to both systems.
+Not all ns-3 models are available from SimGrid (only the TCP and WiFi ones are),
+while not all SimGrid platform files can be used in conjunction ns-3 (routes
+must be of length 1). Also, the platform built in ns-3 from the SimGrid
+description is very basic. Finally, communicating from a host to
+itself is forbidden in ns-3, so every such communication completes
+immediately upon startup.
+
+
Compiling the ns-3/SimGrid binding
**********************************
========================
SimGrid must be recompiled with the ``enable_ns3`` option activated in cmake.
-Optionally, use ``NS3_HINT`` to hint cmake about the path on disk
-where ns-3 is installed.
+Optionally, use ``NS3_HINT`` to tell cmake where ns3 is installed on
+your disk.
.. code-block:: shell
was correctly detected. Otherwise, explore ``CMakeFiles/CMakeOutput.log`` and
``CMakeFiles/CMakeError.log`` to diagnose the problem.
-Test your installation after compilation as follows:
+Test that ns-3 was successfully integrated with the following (from your SimGrid
+build directory). It will run all SimGrid tests that are related to the ns-3
+integration. If no test is run at all, you probably forgot to enable ns-3 in cmake.
.. code-block:: shell
Using ns-3 from SimGrid
***********************
-The SimGrid/ns-3 binding only contains features that are common to both
-systems: ns-3 wireless models are not available, while SimGrid routes
-cannot be longer than 1. Also, the platform built in ns-3 from the
-SimGrid description is very basic.
-
Platform files compatibility
============================
The best solution is to add routers to split your route. Here is an
example of an invalid platform:
-.. code-block:: shell
+.. code-block:: xml
- <platform>
- <zone id="zone0" routing="Full">
+ <?xml version='1.0'?>
+ <!DOCTYPE platform SYSTEM "https://simgrid.org/simgrid.dtd">
+ <platform version="4.1">
+ <zone id="zone0" routing="Floyd">
<host id="alice" speed="1Gf" />
<host id="bob" speed="1Gf" />
- <link id="l1" bw="1Mbps" />
- <link id="l2" bw="1Mbps" />
+ <link id="l1" bandwidth="1Mbps" latency="5ms" />
+ <link id="l2" bandwidth="1Mbps" latency="5ms" />
<route src="alice" dst="bob">
- <link_ctn id="l1"/> <!-- !!!! INVALID WITH ns-3 !!!! -->
- <link_ctn id="l2"/> <!-- !!!! length=2 IS TOO MUCH !!!! -->
+ <link_ctn id="l1"/> <!-- !!!! IGNORED WHEN USED WITH ns-3 !!!! -->
+ <link_ctn id="l2"/> <!-- !!!! ROUTES MUST CONTAIN ONE LINK ONLY !!!! -->
</route>
</zone>
</platform>
This can be reformulated as follows to make it usable with the ns-3 binding.
-There is no direct connection from alice to bob, but that's OK because
-ns-3 automatically routes from point to point.
+There is no direct connection from alice to bob, but that's OK because ns-3
+automatically routes from point to point (using
+``ns3::Ipv4GlobalRoutingHelper::PopulateRoutingTables``).
-.. code-block:: shell
+.. code-block:: xml
- <platform>
+ <?xml version='1.0'?>
+ <!DOCTYPE platform SYSTEM "https://simgrid.org/simgrid.dtd">
+ <platform version="4.1">
<zone id="zone0" routing="Full">
<host id="alice" speed="1Gf" />
<host id="bob" speed="1Gf" />
<router id="r1" /> <!-- routers are compute-less hosts -->
- <link id="l1" bw="1Mbps" />
- <link id="l2" bw="1Mbps" />
+ <link id="l1" bandwidth="1Mbps" latency="5ms"/>
+ <link id="l2" bandwidth="1Mbps" latency="5ms"/>
<route src="alice" dst="r1">
<link_ctn id="l1"/>
</platform>
Once your platform is OK, just change the :ref:`network/model
-<options_model_select>` configuration option to "ns-3" as follows. The rest
-is unchanged.
+<options_model_select>` configuration option to `ns-3` as follows. The other
+options can be used as usual.
.. code-block:: shell
./network-ns3 --cfg=network/model:ns-3 (other parameters)
-Many other files from the ``examples/platform directory`` are usable with the
+Many other files from the ``examples/platform`` directory are usable with the
ns-3 model, such as `examples/platforms/dogbone.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/dogbone.xml>`_.
Check the file `examples/s4u/network-ns3/network-ns3.tesh <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/network-ns3/network-ns3.tesh>`_
to see which ones are used in our regression tests.
+WiFi platforms
+--------------
+
+In SimGrid, WiFi networks are modeled with WiFi zones, where a zone contains
+the access point of the WiFi network and the hosts connected to it (called
+station in the WiFi world). Links inside WiFi zones are modeled as regular
+links with a specific attribute, and these links are then added to routes
+between hosts. The main difference When using ns-3 WiFi networks is that
+the network performance is not given by the link bandwidth and latency but
+by the access point WiFi characteristics, and the distance between the access
+point and the hosts.
+
+So, to declare a new WiFi network, simply declare a zone with the ``WIFI``
+routing.
+
+.. code-block:: xml
+
+ <zone id="SSID_1" routing="WIFI">
+
+Inside this zone you must declare which host or router will be the access point
+of the WiFi network.
+
+.. code-block:: xml
+
+ <prop id="access_point" value="alice"/>
+
+Afterward simply declare the hosts and routers inside the WiFi network. Remember
+that one must have the same name as declared in the property "access point".
+
+.. code-block:: xml
+
+ <router id="alice" speed="1Gf"/>
+ <host id="STA0-0" speed="1Gf"/>
+ <host id="STA0-1" speed="1Gf"/>
+
+Finally, close the WiFi zone.
+
+.. code-block:: xml
+
+ </zone>
+
+The WiFi zone may be connected to another zone using a traditional link and
+a zoneRoute. Note that the connection between two zones is always wired.
+
+.. code-block:: xml
+
+ <link id="wireline" bandwidth="100Mbps" latency="2ms" sharing_policy="SHARED"/>
+
+ <zoneRoute src="SSID_1" dst="SSID_2" gw_src="alice" gw_dst="bob">
+ <link_ctn id="wireline"/>
+ </zoneRoute>
+
+WiFi network performance
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+
+The performance of a wifi network is controlled by 3 property that can be added
+to hosts connected to the wifi zone:
+
+ * ``mcs`` (`Modulation and Coding Scheme <https://en.wikipedia.org/wiki/Link_adaptation>`_)
+ Roughly speaking, it defines the speed at which the access point is
+ exchanging data with all stations. It depends on its model and configuration,
+ and the possible values are listed for example on Wikipedia.
+ |br| By default, ``mcs=3``.
+ It is a property of the WiFi zone.
+ * ``nss`` (Number of Spatial Streams, or `number of antennas <https://en.wikipedia.org/wiki/IEEE_802.11n-2009#Number_of_antennas>`_)
+ defines the amount of simultaneous data streams that the AP can sustain.
+ Not all value of MCS and NSS are valid nor compatible (cf. `802.11n standard <https://en.wikipedia.org/wiki/IEEE_802.11n-2009#Data_rates>`_).
+ |br| By default, ``nss=1``.
+ It is a property of the WiFi zone.
+ * ``wifi_distance`` is the distance from the station to the access point. Each
+ station can have a specific value.
+ |br| By default, ``wifi_distance=10``.
+ It is a property of stations of the WiFi network.
+
+Here is an example of a zone changing ``mcs`` and ``nss`` values.
+
+.. code-block:: xml
+
+ <zone id="SSID_1" routing="WIFI">
+ <prop id="access_point" value="alice"/>
+ <prop id="mcs" value="2"/>
+ <prop id="nss" value="2"/>
+ ...
+ </zone>
+
+Here is an example of a host changing ``wifi_distance`` value.
+
+.. code-block:: xml
+
+ <host id="STA0-0" speed="1Gf">
+ <prop id="wifi_distance" value="37"/>
+ </host>
+
+Random Number Generator
+=======================
+
+It is possible to define a fixed or random seed to the ns3 random number
+generator using the config tag.
+
+.. code-block:: xml
+
+ <?xml version='1.0'?><!DOCTYPE platform SYSTEM "https://simgrid.org/simgrid.dtd">
+ <platform version="4.1">
+ <config>
+ <prop id = "network/model" value = "ns-3" />
+ <prop id = "ns3/seed" value = "time" />
+ </config>
+ ...
+ </platform>
+
+The first property defines that this platform will be used with the ns3 model.
+The second property defines the seed that will be used. Defined to ``time``
+it will use a random seed, defined to a number it will use this number as
+the seed.
+
Limitations
===========
platform. However, there are some known caveats:
* The default values (e.g., TCP parameters) are the ns-3 default values.
- * ns-3 networks are routed using the shortest path algorithm, using
- ``ns3::Ipv4GlobalRoutingHelper::PopulateRoutingTables``.
- * End hosts cannot have more than one interface card. So, your
- SimGrid hosts should be connected to the platform through only
- one link. Otherwise, your SimGrid host will be considered as a
- router.
-
+ * ns-3 networks are routed using the shortest path algorithm, using ``ns3::Ipv4GlobalRoutingHelper::PopulateRoutingTables``.
+ * End hosts cannot have more than one interface card. So, your SimGrid hosts
+ should be connected to the platform through only one link. Otherwise, your
+ SimGrid host will be considered as a router (FIXME: is it still true?).
+
Our goal is to keep the ns-3 plugin of SimGrid as easy (and hopefully readable)
as possible. If the current state does not fit your needs, you should modify
this plugin, and/or create your own plugin from the existing one. If you come up
use routes of length 1, and that any host is connected to the platform.
Arguably, SimGrid could detect this situation and report it, but unfortunately,
this is still to be done.
+
+.. |br| raw:: html
+
+ <br />
