tional entity Responsible for other functions such as paging. Only one signaling entity exists per BSS. NSE One or more NSEs exist per BSS. Each BVC is identified by means of a BVCI, which has end-to-end sig- nificance across the Gb interface. Each BVCI is unique between two peer NSE. In the BSS, it is possible to configure BVCIs statically by administra- tive means or dynamically. In case of dynamic configuration, the BSSGP accepts any BVCI passed by the underlying NSE. Flow Control Procedures The PCU can send flow control messages to the SGSN to change the char- acteristics of the buffers managed by BSSGP (mobile station and BVC buffers) shown in Figure 9-22. That is to say Buffer maximum (Bmax) (the size of the buffer - default value = 72 kilobytes) for the BVCI Rate of flow (R) (the data rate of the leakage - default value = 10 Kbps) for the BVCI Bmax (the size of the buffer - default value = 9 kilobytes) for each mobile station R (the data rate of the leakage - default value = 0 bits) for each mobile station PCU A Figure 9-22 The flow control procedure. MS Bmax BSSGP NSE 0 <<Flow Control> > Bmax; R; MS Bmax; MS R <<Flow Control Ack>> Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. PCUSN-to-SGSN Interface (Gb) PCUSN-to-SGSN Interface (Gb) Each flow control message needs to be acknowledged. The procedure aims at adapting data rate on radio interface (RLC/MAC protocol) to the GPRS network. Mode of Operation The flow control mechanism manages the transfer of BSSGP UNITDATA PDUs sent by the SGSN on the Gb interface to the BSS. The BSS controls the flow of BSSGP UNITDATA PDUs to its BVC buffers by indicating to the SGSN the maximum accepted throughput in total for each BVC. The BSS controls the flow of BSSGP UNITDATA PDUs to the BVC buffer for an individual mobile station by indicating to the SGSN the maximum accepted throughput for a certain