  Understanding of the signatures of cosmic string networks is limited by a
large uncertainty in the sizes at which cosmic string loops form. We review
cosmic string network evolution, and the gravitational signatures, with
emphasis on this uncertainty. We then review a recent analytic model of cosmic
string networks. In combination with recent simulations, this suggests that 90%
of the string goes into very small loops, at the gravitational radiation scale,
and 10% into loops near the Hubble scale. We discuss cosmic string signatures
in such a scenario, and the `inverse problem' of determining the microscopic
cosmic string properties from observations.
