The GPRS Resource System logical network for PDN access, which is con- structed by the protocol SNDPC, one type of GTP messages and IP-and X.25- protocols. 2. The GPRS Resource System logical network for SMS, which is constructed by part of the MAP+TCAP protocol. 3. The GPRS Process Control System logical network, which is constructed by the protocols GMM, MAP+TCAP, BSSAP+ and other types of GTP messages. 4. The GPRS Access Transport Network, which is constructed by the protocols LLC, RLC, MAC, BSSGP and NWS. 5. The GPRS Core Transport Network, which is constructed by UDP and the tunnel mechanism in the GTP protocol. The complete GPRS logical network structure, including the CSPs on which GPRS network is built, will therefore look as shown in Fig. 4.15. GPRS logical networks- Resource System, PDN-accesses IP and {SNDCP,GTP mess.type 255,IP,X.25} X.25 user Process Control System {GMM,BSSAP+,MAP+TCAP,GTPr mess.} {MAP+TCAP} Access transport network Core transport network {LLC,RLC,MAC,BSSGP,NWS} {GTP tunneling, UDP} External CSP SCCP-CSP Internal RF-CSP FR-CSP External CSP (CNL only) IP-CSP External CSP Fig. 4.15 The logical network structure for GPRS 4.4 General Packet Radio Service, a Case Study 4.4.4 The GPRS Standard Like most self-referenced standardized network concepts, the GPRS-standard defines its own terminology. Examples includes the use of the terms interface, ref- erence point, physical node and logical node. Although we do not expect that the SM&AML interpretation of these terms would be used, it is helpful if the meanings of terms that are used are consistent with the usage in other standards and within the standard. The GPRS standard is neither better nor worse than other standards in that respect. It is therefore not correct to conclude that GPRS is poorly described. On the contrary, it is described by ETSI both on an overview level and in great detail. The standards that are GPRS-specific exceed 600 pages; those for MAP are 1000 pages. In addition there are a large number of pages for TCAP and RFCs,