Procedures for bearer capability selection are described in 5.11.3. Procedures for high layer compatibility selection are described in subclause 5.12.3.
Each basic telecommunications service has the required Bearer capability information element encodings, and if applicable the required High layer compatibility information element encodings, defined for that service (e.g. see Recommendation Q.939).
The user (the private ISDN) shall identify the requested teleservices by taking the presented Bearer capability and High layer compatibility information elements in all combinations. Where a combination is not identified as a defined teleservice, that combination shall be ignored. Where a combination is identified as a defined teleservice, that combination may be considered for the purposes of service provision.
The user (the private ISDN) shall identify the requested bearer services from the values of the requested Bearer capability information elements.