The usual role of OpenSIPS is a SIP proxy. In this role, a SIP server—in most cases—can only route requests and replies between user agents. In this chapter, we will explain how to implement SIP services such as call forward and call transfer in this type of an environment. This chapter uses the best practices document RFC 5359, Session Initiation Protocol Service Examples, and assumes that endpoints and gateways support the required RFCs.
One important aspect regarding OpenSIPS is that it does not handle media or RTP. Thus, even simple services such as playing an announcement require an external media server. The most common media servers in use with OpenSIPS are Asterisk™, FreeSWITCH™, and SEMS. In this chapter, you will learn how to implement a series of SIP services integrating OpenSIPS with a media server. We have chosen Asterisk because of its popularity and simplicity.
In this chapter, we will cover the following topics:
Distinguishing where you...