Help on Boundry Conditions of Dielectric in FDTD

Can anyone help me on the boundry conditions in wave propagating from free space into a dielectric. According to electromagnetics, the tangential E-field is continous, but in Dennis Sullivan book on FDTD (chapter 1), he takes D-field to be continous.

Thankx

E=eD
I think since it is in the free space, they both are the same. Please correct me if I am wrong.

At the interface between two arbitrary dielectrics:
Et1=Et2 (tangential)
Dn1-Dn2=rho (normal); most of the time rho=0 (no free charges)

eps1*En1=eps2*En2, so En is discontinuous