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The SBC Core supports the following H.323 components:

Media Encryption of H.323 Calls Using H.235

The SBC adopts the prevailing encryption of H.323 media using H235.6 (excluding SRTP). The RTP header is not encrypted (i.e. "in-the-clear")  while the payload is encrypted. H.235 encryption is call leg independent with the media unencrypted between call legs. The SBC supports AES-128 encryption in Cipher Block Chaining (CBC) mode. The H.245 master, as derived from Master-Slave Determination procedure, generates randomized session keys which are unique per stream and per direction. The session keys are protected while in transit on the network by encryption using the shared secret key derived from the Diffie-Hellman procedure. Media transmitter encrypts media with the session key and media receiver uses the same key for media decryption. The H.245 master sends OLC with session key and the H.245 slave receives session key in OLC Ack from the H.245 master.

Dynamic Payload Type Support for H.323 Calls

The SBC supports G722.1 which does not have statically assigned payload types. Support for G.722.1 includes the 24K and 32K bit rates. Additionally, the SBC supports dynamic payload type assignment for statically allocated payload types such as G.711. This behavior is possible when audiovisual endpoints are encrypting audio stream.

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