Extragalactic jets are produced by super massive black holes in the centers of active galaxies. However, we are still uncertain as to the emission process responsible for the X-ray jets of high power sources such as quasars and FRII radio galaxies. The X-ray emission in the knots along the jet can come from the same population of electrons producing the radio and optical emission, or from IC/CMB emission from a jet with high bulk velocity. The IC/CMB models can be tested using low-frequency radio observations if they have enough resolution and sensitivity to study the spectral properties of individual knots. Here we present a high-resolution study of the jet in 4C19.44 with International LOFAR. The unprecedented low-frequency images with 0.5 arcsec angular resolution between 115 and 185 MHz provide direct information about the origin of the X-ray emission along this jet.