+The purpose of the simgrid::kernel::routing module is to retrieve the
+routing path between two points in a time- and space-efficient manner.
+Indeed, the network model needs both the list of links that the convey
+the created communication, and the summed latency that these links
+represent. This operation is clearly on the critical path of most
+SimGrid simulations.
+
+When defining how the information is routed in the simulated network,
+it is certainly very tempting to use a formalism somehow similar to
+how it is defined on real network. One would have to define the
+routing tables of each routers interconnections sub-networks, just
+like in the real life. Given the daunting amount of configuration
+required, we could complete the information given by the user with
+classical protocols such as BGP and RIP. Many network simulator take
+such configuration as an input, for good reasons.
+
+This is not the way it goes in SimGrid: the network routing is defined
+in a global and compact way instead. This eases the modeling of very
+large systems, and allows highly optimized datastructures and
+algorithms in the simulator. The proposed description mechanism is
+thus much more convinient and efficient. In addition, it is more
+expressive than the classical solution based on forwarding tables on
+each host and router.
+
+The price to pay is that this representation of networks is very
+specific to SimGrid, so you will have to read further to understand
+it, even if you already know how real networks work.
+
+The central notion here are @b Networking @b Zones. NetZones represent
+network areas in which the routing is done in an homogeneous way.
+Conceptually, netzones generalize from the ideas of local networks
+(such as Ethernet switched networks) and Autonomous System. The
+network as a whole is represented as a single hierarchy of netzones,
+meaning that every netzone is part of another netzone (but the @c
+NetRoot, which is the top-level netzone).
+
+The main goal of the routing module is to provide a list of links
+traversed by a given communication and/or a latency to apply. These
+information are then used by the network model to compute the time
+that this communication takes. This information is retrieved by three
+combined algorithms: intra-zone routing, inter-zone routing, and the
+bypass mechanism.