  We analyze scattering of string modes at string junctions of type IIB string
theory. In the infrared limit, certain orthogonal linear combinations of the
fields on the different strings satisfy either Dirichlet or Neumann boundary
conditions. We confirm that the worldsheet theory of a general string network
has eight conserved supercharges in agreement with target space BPS
considerations. As an application, we obtain the band spectrum of some simple
string lattices.
