Proposed basic principle
Fig.2
Basic principle of our proposed system
In our proposed system, two sets of HRA (Half Relay Agent) having special functions inside and outside the private network are established (Fig.2). The inside device is called HRAC (Half Relay Agent Client) and the outside device HRAS (Half Relay Agent Server). These devices perform a function as a set of hypothetical SIP server when dialing. HRAS and HRAC transmit SIP message and voice stream using HTTP tunnel technology, and relay necessary data by HTTP downloading and uploading.As a web access to the outside server from the inside of the company can surely pass through firewall, linkage of HTTP from HRAC to HRAS is easily established in advance. Dialing and voice information of IP phone is conveyed through this HTTP linkage. In our proposed system, communication by means of standard IP phone terminal can be used without modifying the enterprise security policy.
