AudioCodes Mediant 3000 User Manual page 578

Parameter
Web: Master Key Identifier
(MKI) Size
EMS: Packet MKI Size
[SRTPTxPacketMKISize]
[EnableSymmetricMKI]
SIP User's Manual
negotiation of the cipher suite fails, the call is terminated. Incoming
calls that don't include encryption information are rejected.

[2] Disable = The IP Profile for which this parameter is set 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 remote UA can respond
with SRTP or RTP parameters:

If the remote SIP UA does not support SRTP, it uses RTP and
ignores the crypto lines.

In the opposite direction, if the device receives an SDP offer
with a single media (as shown above), 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.
Notes:

Before configuring this parameter, set the EnableMediaSecurity
parameter to 1.

Option [2] Disable is applicable only to IP Profiles.

This parameter can also be configured per IP Profile, using the
IPProfile parameter (see 'Configuring IP Profiles' on page 236).
Defines the size (in bytes) of the Master Key Identifier (MKI) in SRTP
Tx packets.
The range is 0 to 4. The default value is 0.
Enables symmetric MKI negotiation.

[0] = Disabled (default) - the device includes the MKI in its 200 OK
response according to the SRTPTxPacketMKISize parameter (if
set to 0, then it is not included; if set to any other value, it is
included with this value).

[1] = Enabled - 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'). If it 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^
31|1:1
If the device selects a crypto line that does not contain the MKI
parameter, then the MKI parameter is not included in the crypto
line in the SDP answer (even if the SRTPTxPacketMKISize
parameter is set to any value other than 0).
Note: To enable symmetric MKI, the SRTPTxPacketMKISize
parameter must be set to any value other than 0.
578
Description
Document #: LTRT-89712
Mediant 3000