AudioCodes E-SBC User Manual page 435

CHAPTER 19 Coders and Profiles
Parameter
'Gateway Media Security Mode'
media-security-
behaviour
[IpProfile_
MediaSecurityBehaviour]
Mediant 1000 Gateway & E-SBC | User's Manual
Description
If two SBC legs (after offer-answer negotiation) use
different security types (i.e., one RTP and the other
SRTP), the device performs RTP-SRTP transcoding. To
transcode between RTP and SRTP, the following
prerequisites must be met:
■ At least one supported SDP "crypto" attribute and
parameters.
■ [EnableMediaSecurity] parameter must be configured
to [1].
If one of the above transcoding prerequisites is not met,
then:
■ any value other than As is is discarded.
■ if the incoming offer is SRTP, force transcoding, coder
transcoding, and DTMF extensions are not applied.
Defines the handling of SRTP for the SIP entity associated
with the IP Profile.
■ [-1] Not Configured = Applies the settings of the
corresponding global parameter,
MediaSecurityBehaviour.
■ [0] Preferable = (Default) The device initiates
encrypted calls to this SIP entity. However, if
negotiation of the cipher suite fails, an unencrypted call
is established. The device accepts incoming calls
received from the SIP entity that don't include
encryption information.
■ [1] Mandatory = The device initiates encrypted calls to
this SIP entity, but if negotiation of the cipher suite
fails, the call is terminated. The device rejects incoming
calls received from the SIP entity that don't include
encryption information.
■ [2] Disable = This SIP entity does not support
encrypted calls (i.e., SRTP).
■ [3] Preferable - Single Media = The device sends
SDP with a single media ('m=') line only (e.g., m=audio
6000 RTP/AVP 4 0 70 96) with RTP/AVP and crypto
keys. The SIP entity can respond with SRTP or RTP
parameters:
✔
If the SIP entity does not support SRTP, it uses
RTP and ignores the crypto lines.
✔
If the device receives an SDP offer with a single
media (as shown above) from the SIP entity, it
responds with SRTP (RTP/SAVP) if the
EnableMediaSecurity parameter is set to 1. If
SRTP is not supported (i.e., EnableMediaSecurity
is set to 0), it responds with RTP.
✔
If two 'm=' lines are received in the SDP offer, the
device prefers the SAVP (secure audio video
profile), regardless of the order in the SDP.
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