  We study a BPS configuration in which four strings (of different type) meet
at a point in $N = 2, D = 8$ supergravity, i.e., the low energy effective
theory of $T^2$-compactified type II string theory. We demonstrate that the
charge conservation of the four strings implies the vanishing of the net force
(due to the tensions of various strings) at the junction and vice versa, using
the tension formula for $SL(3, Z)$ strings obtained recently by the present
authors. We then show that a general 4-string junction preserves 1/8 of the
spacetime supersymmetries. Using 4-string junctions as building blocks, we
construct a string network which also preserves 1/8 of the spacetime
supersymmetries.
