TLLI is used for addressing at the LLC layer. TLLI is described in clause "NSAPI and TLLI for A/Gb mode".
LLC provides the services necessary to maintain a ciphered data link between an MS and an SGSN. The LLC layer does not support direct communication between two MSs.
The LLC connection is maintained as the MS moves between cells served by the same SGSN. When the MS moves to a cell being served by a different SGSN, the existing connection is released and a new logical connection is established with the new SGSN.
LLC shall be independent of the underlying radio interface protocols. In order to allow LLC to operate with a variety of different radio interface protocols, and to ensure optimum performance, it may be necessary to adjust e.g. the maximum LLC PDU length and the LLC protocol timer values. Such adjustments can be made through negotiation between the MS and the SGSN. The maximum length of an LLC PDU shall not be greater than 1 600 octets minus the BSSGP protocol control information.
The Logical Link Control layer supports:
service primitives allowing the transfer of SNDCP Protocol Data Units (SN PDUs) between the Subnetwork Dependent Convergence layer and the Logical Link Control layer;
procedures for transferring LL PDUs between the MS and SGSN, including:
procedures for unacknowledged delivery of LL PDUs between the MS and the SGSN; and
procedures for acknowledged, reliable delivery of LL PDUs between the MS and SGSN;
procedures for detecting and recovering from lost or corrupted LL PDUs;
procedures for flow control of LL PDUs between the MS and the SGSN; and
procedures for ciphering of LL PDUs. The procedures are applicable to both unacknowledged and acknowledged LL PDU delivery.
The layer functions are organised in such a way that ciphering resides immediately above the RLC/MAC layer in the MS, and immediately above the BSSGP layer in the SGSN.