The modern stage of development of telecommunication networks is characterized by active improvement of routing algorithms in packet-switched networks taking into account the provision of the required quality of service. The need to transfer large amounts of information is due to the need to ensure the normal functioning of modern multimedia applications, in particular such as IP telephony, video and radio broadcasting, interactive distance learning, which determines the multiservice nature of traffic, which is heterogeneous, and its statistical properties in most cases are of a complex polymodal nature. Taking into account the fact that traditional Poisson models providing FIFO servicing of network traffic for solving modern telecommunication problems lead to overly optimistic results in terms of delays, there is a need to develop a new mathematical model of a unidirectional switch providing FIFO servicing of multiservice traffic with polymodal distribution taking into account the provision of the required quality of subscriber service and an algorithm for estimating its main parameters. Development of a mathematical model of a unidirectional switch FIFO-service of multiservice traffic with polymodal distribution taking into account the provision of the required quality of subscriber service and an algorithm for estimating its main parameters. A new mathematical model of a unidirectional switch implementing FIFO-service of multiservice traffic with polymodal distribution has been developed, allowing one to estimate the probabilities that packets arriving at the switch input will not be processed due to overflow of its buffer memory and exceeding the maximum packet processing time. The model takes into account the delays introduced by the channel and channel equipment during the distribution and processing of packets from the source to the switch in question. Recommendations for modeling traffic processing to ensure the specified accuracy of the results are presented.