The present disclosure relates to a method performed in a Radio Access Network (RAN) 2 comprised in a communication network, for locating a communication bottleneck in said communication network. The method comprises estimating a first Round Trip Time (RTT) between the RAN and a terminal device 4 connected via the RAN. The method also comprises estimating a second RTT between the RAN and a server 6 of a service provider configured for providing a service to the terminal device via the RAN. The method also comprises estimating an end-to-end RTT between the terminal device and the server, based on the first RTT and the second RTT. The method also comprises determining a relative contribution of the second RTT to the end-to-end RTT. The method also comprises determining that the relative contribution of the second RTT indicates that signalling performance between the server and the terminal device is limited by the signalling performance between the server and the RAN.