This project extends the capabilities of JAIN-SIP by using DNS procedures detailed in RFC 3263 to enable a UAC to determine the IP address (including IPv6), port and transport protocol of the next hop for a SIP request.

Why should I care about using DNS in SIP?

Firstly, using DNS to determine the next hop allows you to understand the capabilities of the SIP entity to which you're routing a request. RFC 3263 provides a mechanism for a SIP server to advertise what transports it supports, and in what preference. So if you need to route to a server that only supports TLS, you can do that without any local configuration.

Secondly, RFC 3263 provides the ability for a server to identify secondary hosts, for failover and load-balancing purposes. So if the server you're trying to contact suddenly fails, you can pick a new one with no loss of service.

How do I use it?

Adding DNS support to your JAIN-SIP user agent is extremely simple, and often requires changing only one line of code. To use the router from this project in your JAIN-SIP application, add the latest JAR to your application's classpath, and create a new SipStack like so:

Properties properties = new Properties();
properties.setProperty("javax.sip.ROUTER_PATH", "com.google.code.rfc3263.DefaultRouter");

SipFactory sipFactory = SipFactory.getInstance();
SipStack sipStack = sipFactory.createSipStack(properties);

For more information, please visit the usage page.

ENUM Support

If you want ENUM support too, consider looking at the JAIN-SIP Extension project.