Date Added: May 2012
In the Session Initiation Protocol (SIP), payments have been proposed as a way for vendors to obtain profit from the services they provide. Payments in SIP have also been proposed for microbilling and even as a solution to SPAM in VoIP systems. Although, several proposals exist for making payments in SIP, they present some limitations when the authors want to pay for access to real-time services: either they are not suitable for micropayments or they do not consider security in the payment information exchanged. As a response to these limitations, they propose a new SIP payment protocol, LP-SIP, that supports the payment according to different models like pay-per-time, session-based, etc.