SRTP

SRTP stands for Secure Real-time Transport Protocol. It is the encrypted version of RTP, the protocol that carries the actual voice on a call. Plain RTP sends audio across the network in the clear, which means anyone able to capture the packets could, in theory, reassemble and listen to the conversation. SRTP scrambles that stream so the audio is unreadable to anyone who does not hold the key.

Encryption matters in a call center because conversations often include names, account details, or payment information. SRTP protects the talking part of the call, but it only covers the audio. The setup messages, where the call is dialed and answered, travel over SIP (Session Initiation Protocol) and need their own protection.

SRTP and signaling go together

For a fully private call you want SRTP for the audio and SIP over TLS (SIP over TLS) for the signaling. One without the other leaves a gap: encrypt only the signaling and the voice is still exposed; encrypt only the audio and the call details can still be read. Used as a pair, they give you a VoIP call that is private from end to end.

Encryption adds a small amount of processing on each end, but on modern hardware the cost is negligible and it does not change which Codec you use. SRTP does not fix quality problems on its own; issues like Packet loss still come through, just encrypted. Check that both your carrier and your phones support SRTP before turning it on, since both sides have to agree to use it.

It is worth being clear about what SRTP does and does not protect. It scrambles the audio while it travels across the network, so someone snooping on the wire cannot listen in. It does not encrypt the recording once it is saved to disk, and it does not stop a supervisor with the right access from using Barge-in or Call monitoring to join a live call. Those are separate controls. If your goal is keeping conversations private from outsiders on the network, SRTP is the right tool; if your goal is also protecting stored audio, you handle that with how and where the Call recording files are kept. Knowing the difference saves you from assuming one setting covers everything.