Open Unified Communication: Protocols
The most important part of building a long-term communication platform for your organization is standardizing on a set of communication protocols for all components. Open protocols are the foundation for the Internet. Interoperability is the most important property of the protocol implementation. You need to make sure that the various components talk with each other, regardless of vendor or Open Source project. Using a protocol standardized by the IETF, the engineering team that sets the Internet standards, you are on your way towards securing your investment.
SIP – the session initiation protocol
SIP is a protocol made for realtime IP communication. The core function of the protocol is to organize a rendevous, a meeting between session participants. The session can be audio, video, chat or something else. SIP is a protocol that is application generic. IP telephony is only one, albeit the most commonly used, application. Standardising on SIP you are not only building a “PSTN over IP” network, you are building a foundation for all kinds of IP communication.
SIP-based PSTN access – “SIP Trunking”
Today SIP is mostly used for access to the telephony network. Delivering PSTN access over SIP is quickly replacing ISDN E1/T1 phone trunks. This is an easy way to lower costs and migrating to IP based communication. Unfortunately, since this is often the first SIP application, the architecture for the SIP platform is tied to this application. This makes it harder to add future applications and Internet telephony to the architecture. In Open Unified Communication, you build the platform in a generic way and then add the PSTN telephony as an application on top of the architecture.
RTP – the realtime media transport
RTP, the realtime protocol, and SRTP, the encrypted version, builds the realtime delivery platform on IP networks. It’s designed for video, audio and text. RTP is used by many realtime applications, including SIP multimedia sessions. The RTP protocol can handle many different networks and have functions for redundancy, compressions, trunking and security. SIP calls set up bidirectional multimedia streams using RTP.
The SIP platform does not stand alone. It builds on years of work in the IETF, developing the Internet protocol architecture. HTTP is integrated in many ways, both in address book management in the SIMPLE presence platform and for verifying certificates in SIP identity. LDAP is commonly used for managing user identities both in standalone directories and by connecting to Microsoft Active Directory. These are just a few of the protocols in the SIP infrastructure.