The procedures currently described in this Recommendation are for the control of circuit-switched connections, user-to-user signalling connections, and packet-switched connections. The transport of other message-based information flows on the D-channel is a subject for further study and will be included in related Recommendations.
NOTES
1. The term "layer 3" is used for the functions and protocol described in this Recommendation [see Recommendation Q.930 (I.450)]. The terms "data link layer" and "layer 2" are used interchangeably to refer to the layer immediately below layer 3.
2. Alignment of the functions and protocol with those of OSI network layer is for further study.