he 3G- GPRS with WCDMA radio interface. Although architectural differences between these two systems exist, the procedures and concepts are very similar. The EPS network architecture is the newest 3GPP network architecture family mem- ber with the new LTE radio interface. 3GPP has specified two variants of the EPS architecture - the GTP, and the PMIP variant. EPS uses a new network architecture with significant changes from the GPRS architecture. However, due to the common pedigree similarities between the architectures also exist. The main difference in the philosophy between the GPRS and EPS is that the EPS does not have the CS mode and the default bearer establishment is part of the EPS network attachment procedure, whereas in GPRS the PDP Context has to be activated separately. Both architectures support primary network connections - Primary PDP Context in GPRS, and default EPS Bearer in EPS. In addition, both architectures support secondary connections, for instance for QoS reasons - Secondary PDP Context in GPRS, and dedi- cated EPS Bearer in EPS. APNs are used for selecting the PDN where the sessions (PDP Context, or EPS Bearer) are connected. The TFT is used to decide into which Secondary PDP Context or Dedicated EPS Bearer the traffic is directed. 2.10 Suggested Reading WCDMA for UMTS: HSPA Evolution and LTE, H. Holma and A. Toskala. LTE for UMTS: Evolution to LTE-Advanced, H. Holma and A. Toskala Voice over LTE (VoLTE), M. Poikselkä, H. Holma, J. Hongisto and J. Kallio SAE and the Evolved Packet Core: Driving the Mobile Broadband Revolution, M. Olsson, S. Sultana, S. Rommer, L. Frid, C. Mulligan The IMS: IP Multimedia Concepts and Services, M. Poikselkä and G. Mayer The 3G IP Multimedia Subsystem (IMS): Merging the Internet and the Cellular Worlds, G. Camarillo and M-A. Garcia-Martin Deploying IPv6 in 3GPP Networks References 1. 3GPP. 3rd Generation Partnership Project, http://www.3gpp.org/ 2. ARIB. Association of Radio Industries and Businesses, http://www.arib.or.jp/english/. 3. ATIS. Alliance for Tel