The following recommendations are made on the use of cause values.q931 标准的报错解释：1) When the calling user or called user is not an authorized subscriber of the multirate circuit-mode bearer capability, cause No. 57 bearer capability not authorized shall be returned to the calling user.2) When a network (public or private)cannot support the specified transfer rate or bearer capability, cause No. 65 bearer capability not implemented shall be returned to the calling user.3) When there are insufficient channels on a single interface to support the information transfer rate requested, cause No. 34 no circuit/channel available or cause No. 17 user busy shall be returned to the calling user (see Recommendation Q.850 which is also reproduced in Appendix I).
