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The H.245 messages are encapsulated into H.225 messages within a special header called H245Control as described by ASN.1. The H245Control header can be added to any message except initial Setup message. However, if there are no other messages to be shipped out from an endpoint, a designated Facility message is used. (H.323 V2 accepts and defines Empty Facility message) as transport vehicle to carry on H.245 contents.