The Secure Real-Time Transport Protocol (SRTP), is an extension profile of Real-Time Transport Protocol (RTP) which adds further security features, such as encryption, message authentication, confidentiality, and replay protection.
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SDES Security parameters and keys to set up SRTP sessions are exchanged in clear text in form of SDP attributes, hence relying on the signaling plane to secure the SDP message using TLS, for instance.
MIKEY Performs the key exchange and negotiates cryptographic parameters on behalf of multimedia applications. Its messages are transported in the SDP payload and encoded in base64.
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DTLS Enables the exchange of the cryptographic parameters and derives keying material. The key exchange takes place in the media plane and is multiplexed on the same ports as the media itself. We will elaborate on this in a future post, but, in short, once some of the ICE checks have been completed, DTLS-SRTP allows the SRTP media channel to be established with no need to reveal keys in the SDP message exchange as is done with SDES.
The Peeredge Switch SBC supports SDES and DTLS to negotiate SRTP parameters.