-Note the way in which hosts, links, and routes are defined in
-this XML. All hosts are defined with a speed (in Gflops), and links
-with a latency (in us) and bandwidth (in MBytes per second). Other
-units are possible and written as expected. Routes specify the list of
-links encountered from one route to another. Routes are symmetrical by
-default.
+The elements basic elements (with :ref:`pf_tag_host` and
+:ref:`pf_tag_link`) are described first, and then the routes between
+any pair of hosts are explicitely given with :ref:`pf_tag_route`. Any
+host must be given a computational speed (in flops) while links must
+be given a latency (in seconds) and a bandwidth (in bytes per
+second). Note that you can write 1Gflops instead of 1000000000flops,
+and similar. Last point: :ref:`pf_tag_route`s are symmetrical by
+default (but this can be changed).