Based on carriers that cannot be copied or eavesdropped without notice to the communicating parties, quantum key distribution (QKD) allows remote users to establish shared encryption keys with information-theoretic security. A prerequisite for the widespread adoption of QKD systems as a quantum-safe cryptography solution is that they allow for easy networking. A variant of QKD that relies on single-photon interference, called twin-field (TF) QKD, enables key generation over unprecedented channel losses, offering a promising approach to metropolitan quantum networks that consist of long fibers and several lossy nodes. We present advancements on experimental TF-QKD based on a Sagnac interferometer. By managing the noise sources that previously restricted this platform to a fiber distance of 10 km, we enable a highly practical TF-QKD network spanning 127 km. We also simulate QKD performance under packet switching, which is the dominant mode of operation for today’s Internet and thus an important step towards integration with existing classical network infrastructure. By developing a general framework for key rate optimization in a packet-switched network, we show that packet-switched QKD is feasible under realistic network conditions and hardware limitations.