2.1. User Agents
2.2. Proxy Server
2.3. Redirect Server
2.4. Registrar
2.5. Back to Back UA
3.1. Call
3.2. Dialog
3.3. Transaction
4.1. SIP Request messages
4.2. SIP Request messages
6.1. SIP Header extensions
6.2. SIP Request extensions
7.1. Direct UA to UA session setup
7.2. Simple session with two stateful proxy-servers
7.3. Session establishment with two stateless proxies
7.4. Stateless vs stateful proxies
7.5. Redirect server
7.6. Calling party abandon
7.7. Called party busy
7.8. Called party no reply
7.9. SIP to ISUP call
7.10. SIP registration