This book constitutes revised selected papers from the 24th International Conference on Distributed and Computer and Communication Networks, DCCN 2021, held in Moscow, Russia, in September 2021. Due to the COVID-19 pandemic the conference was held online. The 31 full papers along with the 4 short papers were carefully reviewed and selected from 151 submissions.The papers are organized in the following topical sections: computer and communication networks; analytical modeling of distributed systems, and distributed systems applications.