When using the web, large response times are bones of contention for users, i.e. they damp the Quality of Experience (QoE). Though, if one knew the cause of a large response time, one can examine what can be done about this obstacle. In this paper, we determine the weak point of the Extensible Authentication Protocol Method for GSM Subscriber Identity Modules (EAP-SIM) with the OpenID service with regards to excessive authentication times, which determine the response times. In order to provoke controlled raises of latter, we emulate bad network performance by introducing bi-directional delay between the supplicant (client) and the authenticator (server). Based on a recent, exponential relationship between QoE and response time, we then identify, quantify and compare the decisive factors for QoE reduction as functions of the components of the authentication times. The results we obtain clearly show that one task of the authentication contributes significantly more to the total response times than the other task, which points out the direction for future optimisation of user perception of authentication times.