We transferred the frequency of an ultrastable laser over a $108\text{-}\mathrm{km}$ -long urban fiber link comprising $22\mathrm{km}$ of an optical communications network fiber simultaneously carrying Internet data traffic. The metrological signal and the digital data signal were transferred over two different frequency channels in a dense wavelength-division multiplexing scheme. The metrological signal was inserted in and extracted from the communication network using bidirectional off-the-shelf optical add–drop multiplexers. The link-induced phase noise was measured and canceled with a round-trip technique using an all-fiber-based interferometer. The compensated link showed an Allan deviation of a few ${10}^{-16}$ at 1 s and below ${10}^{-19}$ at $\mathrm{10,000}\mathrm{s}$ . This work paves the way to a wide dissemination of ultrastable optical clock signals between distant laboratories via the Internet.