AudioCodes Mediant 4000 SBC User Manual page 420

Parameter
Index
[IpProfile_Index]
Name
profile-name
[IpProfile_ProfileName]
Media Security
SBC Media Security Mode
sbc-media-security-
behaviour
[IpProfile_SBCMediaSecurit
yBehaviour]
Symmetric MKI
enable-symmetric-mki
[IpProfile_EnableSymmetric
MKI]
User's Manual
Defines an index number for the new table row.
Note: Each row must be configured with a unique index.
Defines a descriptive name, which is used when associating the row in
other tables.
The valid value is a string of up to 40 characters.
Defines the handling of RTP and SRTP for the SIP entity associated
with the IP Profile.

[0] As is = (Default) No special handling for RTP\SRTP is done.

[1] SRTP = SBC legs negotiate only SRTP media lines, and RTP
media lines are removed from the incoming SDP offer-answer.

[2] RTP = SBC legs negotiate only RTP media lines, and SRTP
media lines are removed from the incoming offer-answer.

[3] Both = Each offer-answer is extended (if not already) to two
media lines - one RTP and the other SRTP.
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 must be set 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.
Enables symmetric MKI negotiation.

[0] Disable = (Default) The device includes the MKI in its SIP 200
OK response according to the SRTPTxPacketMKISize parameter
(if set to 0, it is not included; if set to any other value, it is included
with this value).

[1] Enable = The answer crypto line contains (or excludes) an MKI
value according to the selected crypto line in the offer. For
example, assume that the device receives an INVITE containing
the following two crypto lines in SDP:
a=crypto:2 AES_CM_128_HMAC_SHA1_80
inline:TAaxNnQt8/qLQMnDuG4vxYfWl6K7eBK/ufk04pR4|2^
31|1:1
a=crypto:3 AES_CM_128_HMAC_SHA1_80
inline:bnuYZnMxSfUiGitviWJZmzr7OF3AiRO0l5Vnh0kH|2^
31
The first crypto line includes the MKI parameter "1:1". In the 200
OK response, the device selects one of the crypto lines (i.e., '2' or
'3'). Typically, it selects the first line that supports the crypto suite.
However, for SRTP-to-SRTP in SBC sessions, it can be
determined by the remote side on the outgoing leg. If the device
selects crypto line '2', it includes the MKI parameter in its answer
SDP, for example:
a=crypto:2 AES_CM_128_HMAC_SHA1_80
inline:R1VyA1xV/qwBjkEklu4kSJyl3wCtYeZLq1/QFuxw|2^
420
Mediant 4000 SBC
Description
Document #: LTRT-40203