| The design is such that SIP clients use TCP and UDP | | | | central network architecture and dumb endpoints; |
| port 5060 to connect the SIP servers and others SIP | | | | therefore it requires only a very simple core network |
| endpoints. The sole purpose of SIP uses are setting up | | | | with intelligence distributed to the network edge, |
| and tearing down voice or video calls. Where session | | | | embedded. The features of SIP are implemented as |
| initiation is required, however, SIP is used as well. | | | | compared to traditional SS7 features, which are |
| These include Event Subscription and Notification, | | | | implemented in the network. |
| Terminal mobility and so on. A lot of SIP-related RFCs | | | | SIP is characterized by its proponents as having roots |
| actually define behaviour for such solutions. All voice | | | | in the IP community rather than the telecom industry |
| video communications are done over separate session | | | | although many other VoIP signaling protocols exist. |
| protocols, like RTP. | | | | While the H. 323 VoIP protocol has been traditionally |
| SIP was tasked to provide a signaling and call setup | | | | more associated with the ITU, SIP has been |
| protocol for IP-based communications that can support | | | | standardized and governed primarily by the IETF. The |
| a superset of the call processing functions and | | | | two organizations have endorsed both protocols in |
| features present in the Public Switched Telephone | | | | some fashion. |
| Network (PSTN). The SIP Protocol by itself, defines | | | | SIP is like HTTP and shares some of its design |
| the focus of the call-setup and signaling. However, it | | | | principles as well. Things like readable by humans and |
| has been designed to enable the building of these | | | | request-response structured. Codes like '404 not |
| featured network elements called Proxy Servers and | | | | found' are used as well. SIP is much simpler than H. |
| User Agents. As such, these are features that permit | | | | 323. However, some would counter that while SIP has |
| familiar telephone-like operations: dialing, ringing, hearing | | | | a goal for simplicity, its current state is as complex as |
| ring tones or busy signals. The implementation might be | | | | H. 323. It is a stateless control, that some might point |
| different but the behaviour is similar. | | | | out, hence making it possible to fail like other difficult |
| SIP enabled telephony networks can also implement | | | | protocols as well. SIP and H. 323 are not limited to |
| many of the more advanced call processing features | | | | voice communication but can mediate any kind of |
| present in SS7 (Signaling System 7), though the two | | | | communication session from voice to video, maybe |
| protocols themselves are different. SIP is a | | | | even unrealized applications in future. |
| peer-to-peer protocol, characterized by highly complex | | | | |