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Spacevars
0 series4

supports DTLS-SRTP and is extended to allow a relay mechanism that transparently passes the DTLS, SRTP, and SRTCP packets end-to-end without DTLS certification or SRTP cryptographic encryption and decryption taking place at SBC

Spacevars
0 product

. When SBC is configured to relay DTLS-SRTP, the endpoints establish DTLS association using each other’s credentials, which are transparently passed by SBC in the SDP of the SIP signaling messages. Encryption and decryption of the SRTP and SRTCP packets take place at the endpoints based on the cryptographic credentials passed through DTLS. If media transcoding, DTMF interworking, or Lawful Intercept (LI) processing is required on the session, as determined during the initial invite or offer call negotiation stage DTLS-SRTP is not relayed.

Enable dtlsSrtpRelay on both legs of the call for DTLS-/SRTP stream to be relayed.

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This feature also adds relay support for DTLS/-SCTP media streams that is not based on RTP but relayed transparently by SBC. When SBC is configured to relay DTLS/-SCTP, the DTLS and SCTP packets are transparently passed end-to-end and the peer endpoints establish the DTLS association using each other’s credentials, which are transparently passed by SBC in the SDP of the SIP signaling messages.

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When DTLS-SRTP and/or DTLS/-SCTP stream requires ICE to traverse NAT, the relay mechanism is supported with ICE procedures terminated locally at SBC. DTLS-SRTP and/or DTLS-SCTP packets are transparently passed by SBC once SBC, once ICE processing is complete.

DTLS-SCTP stream is logged in call detail record Call Detail Record (CDR) as UDP/DTLS/SCTP in fields 230/231. When a DTLS-SRTP stream is relayed, it is indicated in fields 242/243 where 1 indicates the stream is terminated and 2 indicates the stream is relayed.

Warning
title Warning
When a session contains DTLS-SRTP video stream or DTLS/-SCTP application stream and there is no audio stream specified, SBC allows the session when the ingress and egress Packet Service Profiles (PSP) are configured as audio pass-through.

Info
In case of WRTC, when ICE is part of session establishment, the relay mechanism implemented for DTLS-SRTP and DTLS/-SCTP is supported independent of ICE processing.

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