H.225.0 is a substandard of H.323.

The main concern of H.225 is the definition of news:

  • Call signaling: Establish, monitor and terminate an H.323 call. Call signaling of H.225 is based on the ISDN call procedures, standard Q.931.
  • RAS signaling function: Perform registration, access, bandwidth changes, status and logout procedures between endpoints and an H.323 gatekeeper. This amount of messages is called RAS (Registration Admission and Status ). The RAS signaling function uses a separate channel.

The encoding of the message is done using the Q.931 user-to -user information element. The messages themselves are coded in accordance with the Packed Encoding Rules (PER) of ASN.1.

  • Network protocol
  • ITU Recommendation