ETSI - TS 124 022
Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile Telecommunications System (UMTS); Radio Link Protocol (RLP) for circuit switched bearer and teleservices
|Publication Date:||1 August 2020|
The present document specifies the Radio Link Protocol (RLP) for circuit switched data transmission within a PLMN. RLP covers the Layer 2 functionality of the ISO OSI Reference Model (ISO/IEC 7498 ). It is based on ideas contained in ISO/IEC 3309 , ISO/IEC 4335  and ISO/IEC 7809  (HDLC of ISO) as well as ITU-T Recommendation X.25  and Q.92x (LAP-B and LAP-D of ITU, respectively.) RLP has been tailored to the special needs of digital radio transmission. RLP provides to its users the OSI Data Link Service (ISO/IEC 8886 ).
RLP is intended for use with non-transparent data-transfer. Protocol conversion may be provided for a variety of protocol configurations. Those foreseen immediately are:
- character-mode protocols using start-stop transmission (IA5);
- X.25 LAP-B.
For reasons of better presentation, material about protocol conversion has been placed within those Specifications concerned with the relevant Terminal Adapters, i.e. 3GPP TS 27.002  for the asynchronous case and 3GPP TS 27.003  for the synchronous case. Care must be taken that that material also applies to Interworking Functions; see 3GPP TS 29.007 .
The present document is valid for a PLMN in A/Gb mode as well as in Iu mode. If text applies only for one of these systems it is explicitly mentioned by using the terms "A/Gb mode" and "Iu mode". Please note, that the Gb interface does not play any role in the scope of the present document although the term "A/Gb mode" is used.