-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).
+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 and a bandwidth. You can write 1Gf for
+1,000,000,000 flops (full list of units in the reference guide of
+:ref:`pf_tag_host` and :ref:`pf_tag_link`).
+
+Routes defined with :ref:`pf_tag_route` are symmetrical by default,
+meaning that the list of traversed links from A to B is the same as
+from B to A. Explicitely define non-symmetrical routes if you prefer.
