The main signaling protocol for IP Multimedia Subsystem is Session Initiation Protocol. A typical procedure for a session establishment involves two types of signaling messages with different priority: Invite message, which initiate a session, and non-Invite messages, which continue session establishment. In the paper for the analysis of two types signaling messages service process the single server asymmetric polling system with two infinite queues and a non-zero switching time is proposed. We estimate the waiting time for the gated and the exhaustive service disciplines using input data applicable to signaling traffic analysis. For the exhaustive discipline the formulas for the second moments of the waiting time were obtained and calculation of the first and the second moments of the waiting time was carried out. © Springer International Publishing Switzerland 2015.