4 Data Link Layer

25.4243GPPRelease 17TSUTRAN Iur interface data transport & transport signalling for Common Transport Channel data streams

4.1 ATM Transport Option

ATM shall be used in the transport network user plane and the transport network control plane according to ITU‑T Recommendation I.361 [1]. The structure of the cell header used in the UTRAN Iur interface is the cell header format and encoding at NNI (see Figure 3/I.361 [1]).

4.2 IP Transport Option

A UTRAN Node supporting IP transport option shall support PPP protocol with HDLC framing (IETF RFC 1661 [10], IETF RFC 1662 [11]).

Note: This does not preclude the single implementation and use of any other data link layer protocols (e.g. PPPMux/AAL5/ATM (IETF RFC 3153 [20], IETF RFC 2364 [21]), PPP/AAL2/ATM, Ethernet, MPLS/ATM (IETF RFC 3031 [22]), etc.) fulfilling the UTRAN requirements toward the upper layers.

An RNC using IP transport option having interfaces connected via slow bandwidth PPP links like E1/T1/J1 shall also support IP Header Compression (IETF RFC 2507 [12]) and the PPP extensions ML/MC-PPP (IETF RFC 1990 [13]), (IETF RFC 2686 [14]). In this case, negotiation of header compression (IETF RFC 2507 [12]) over PPP shall be performed via IETF RFC 2509 [15].