Petri Net Modeling of SIP of Traversing NAT Based on STUN

Petri net is widely used in the simulation and analysis of the discrete event systems because of the features such as intuition, simplicity and understandability. The paper used Petri net to model and analyse SIP protocol of traversing NAT. Firstly the paper proposed using STUN to implement the NAT traversal of SIP protocol and simply introduced the advantages of Petri net modeling, then introduced the related knowledge of SIP and NAT and pointed out the impact of NAT on SIP protocol, and then detailedly described the SIP session interaction process of traversing NAT based on STUN, finally this process was modeled using Petri net and further made the reach ability analysis. In this way, the paper clearly and intuitively showed the voice communication process between the private network hosts by SIP protocol.