Megaco (a contraction of “Media Gateway Controller”) is a signalling protocol, used between a Media Gateway and a Media Gateway Controller (also known as a Call Agent or a Soft Switch) in a VoIP network. It defines the necessary signalling mechanism to allow a Media Gateway Controller (Call agent) to control gateways in order to support voice/fax calls between PSTN-IP or IP-IP networks.
The protocol is defined by IETF RFC 3525 and was the result of joint work of IETF and ITU. It is also known as H.248. H.248 is the name given to it by the ITU, Megaco is the IETF name.
The Real-time Transport Protocol (or RTP) defines a standardized packet format for delivering audio and video over the Internet. It was developed by the Audio-Video Transport Working Group of the IETF and first published in 1996 as RFC 1889 which was obsoleted in 2003 by RFC 3550.
RTP does not have a standard TCP or UDP port on which it communicates. The only standard that it obeys is that UDP communications are done via an even port and the next higher odd port is used for RTP Control Protocol (RTCP) communications. Although there are no standards assigned, RTP is generally configured to use ports 16384-32767. RTP can carry any data with real-time characteristics, such as interactive audio and video. Call setup and tear-down is usually performed by the SIP protocol. The fact that RTP uses a dynamic port range makes it difficult for it to traverse firewalls. In order to get around this problem, it is often necessary to set up a STUN server.
From Wikipedia:
Transport Layer Security (TLS) and its predecessor, Secure Sockets Layer (SSL), are cryptographic protocols which provide secure communications on the Internet for such things as web browsing, e-mail, Internet faxing, instant messaging and other data transfers. There are slight differences between SSL 3.0 and TLS 1.0, but the protocol remains substantially the same. The term “TLS” as used here applies to both protocols unless clarified by context.
The TLS protocol(s) allow applications to communicate across a network in a way designed to prevent eavesdropping, tampering, and message forgery. TLS provides endpoint authentication and communications privacy over the Internet using cryptography. Typically, only the server is authenticated (i.e., its identity is ensured) while the client remains unauthenticated; this means that the end user (whether an individual or an application, such as a Web browser) can be sure with whom they are communicating. The next level of security — in which both ends of the “conversation” are sure with whom they are communicating — is known as mutual authentication. Mutual authentication requires public key infrastructure (PKI) deployment to clients. TLS involves three basic phases:
1. Peer negotiation for algorithm support
2. Public key encryption key-based exchange and certificate-based authentication
3. Symmetric cipher traffic-based encryption
SIGTRAN is the name given to an IETF working group that produced specifications for a family of protocols that provide reliable datagram service and user layer adaptations for SS7 and ISDN communications protocols. The most significant protocol defined by the SIGTRAN group was the Stream Control Transmission Protocol (SCTP), which is used to carry PSTN signalling over IP.
The SIGTRAN group was significantly influenced by telecommunications engineers intent on using the new protocols for adapting VoIP networks to the PSTN with special regard to signaling applications. Recently, SCTP is finding applications beyond its original purpose wherever reliable datagram service is desired.
