Media security is obtained by using Secure RTP (SRTP) and Secure RTCP (SRTCP). SRTP encrypts the media content based on a secure key and SRTCP provides statistics and control operations.
Note:
Media security is not available on the following phones for the G.711 10ms, G.723 10ms, and G.729 10ms payloads.
200x series phase 0/1 phones
IP Desk phones 1210, 1220, and 1230
CS 1000 provided the ability to maintain media security by using Secure RTP (SRTP) and Secure RTCP (SRTCP) instead of the insecure base version. This was controlled by a setting in the CS 1000 configuration as the Media Security System default. This could be done by using either the CLI or Element Manager. In either case the system can be set as:
Never (MSNV)
Best effort (MSBT)
Always (MSAW)
This could also be applied to individual IP endpoints as a class of service, overriding the system default. However, the IP stations can also be set explicitly to use the system default (MSSD), and when that changes, the IP station changes as well.
With the Device Adapter, an equivalent operation exists. The cluster can be set with a cluster attribute. For more information, see Setting the media security policy.
When the setting is Always, any INVITE generated by Device Adapter is sent with only SRTP requested in the Session Description Protocol data. If the setting is Never, only RTP is requested. However, with Best Effort, both options are requested.
The endpoint also has the option of using media security different from the system setting, through the Features field. Enter the applicable CS 1000 class-of-service mnemonic as a feature.
