<host id="alice" speed="1Gf"/> <!-- connected to an in-file speed trace -->
<host id="bob" speed="1Gf"/> <!-- connected to an out-file speed trace -->
<host id="carol" speed="500Mf" state_file="carol.fail"/> <!-- out-file state trace as attribute -->
<host id="alice" speed="1Gf"/> <!-- connected to an in-file speed trace -->
<host id="bob" speed="1Gf"/> <!-- connected to an out-file speed trace -->
<host id="carol" speed="500Mf" state_file="carol.fail"/> <!-- out-file state trace as attribute -->