EPC Protocols and Procedures

3 days

Download brochureThe course provides a complete overview of the Evolved Packet Core (EPC) protocols and procedures covering both EPC signaling towards E-UTRAN as well as towards IMS direction. A thorough consideration of IMS protocols, procedures and services is presented. Security in EPC and IMS is discussed with great detail. Then, Policy and Charging Control for EPS and IMS is discussed. The course is concluded with the explanation of EPS Interworking with other networks, which includes discussion of S3 and S4 interfaces, as well as presentation of the representative interworking cases.

Introduction to EPS

• Evolution steps of the 3GPP systems, the goals for LTE/SAE
• Current status of the EPS standardization process

EPS Network Architecture

• IP in the Core Network
• Nodes and their roles: UE, eNB, SGW, MME, PGW, PCRF, HSS
• Interfaces: Uu, X2, S1, S11, S5, Gx, S6a, SGi, Rx
• Overview of EPC protocols: GTP, X2AP, S1-AP, S1-MME, GTP, Diameter
• IP connectivity, user plane and control plane
• Access Stratum signaling and Non-Access Stratum signaling

Evolved Packet Core Protocols

• NAS protocols (EMM and ESM)
• EMM, ECM and RRC states and state transitions
• Subscriber identities and their relations (IMEI, IMSI, GUTI, S-TMSI, RNTIs)
• Control plane EPC protocols: S1-AP and GTP-C over SCTP
• User plane EPC protocols: GTP-U over UDP
• S1 Application Protocol (S1AP) procedures
• Main GTP procedures in EPS
• The GTP version 2 protocol (eGTP)
• General message headers

Evolved Packet Core Procedures

• Mobility management (Tracking Area Update)
• MMEs in the Pool (pool area, MME selection and addressing, load balancing, overload control)
• Network Attach and Detach
• Session establishment and control (call establishment procedure)
• QoS related procedures (default and dedicated bearer, QoS Parameters, PDN Connectivity Request and EPS Bearer Establishment)
• User data transfer (GTP tunneling concept, tunnel establishment)
• Service request procedure (UE- and network-triggered)

IMS Protocols

• IMS architecture and nodes (S-CSCF, P-CSCF, I-CSCF, AS, HSS, MRFC, MRFP, etc)
• Control plane protocols: SIP and SDP
• User plane protocols: RTP and RTCP
• End-to-end IMS protocol stack
• UICC and ISIM and USIM (Subscriber modules)
• Public and private user identities
• IP in the EPS/IMS (IETF Dependence, dynamic UE address allocation)
• User profiles (IMS service profile) and filter criteria

IMS Procedures and Services

• Service Control and the IMS
• Charging Requirements and Functionality (AAA charging example)
• IMS discovery
• SIP signaling procedures – registration, invitation, security
• End-to-end call establishment via IMS
• Services: SMS, Voice (CS Fallback, Voice Call Continuity, VoLGA)

Security in EPS and IMS

• Security architecture (key hierarchy) and keys' derivation
• Integrity and encryption - SNOW 3G, AES
• Key distribution and mobility aspects
• EPS authentication (AAA procedures)
• User-to-Network security mechanisms
• Network domain security mechanisms (IPsec in EPS and IMS with ESP and IKE)
• The IMS security architecture
• Diameter protocol, commands, applications and Attribute Value Pairs
• Diameter nodes and 3GPP extensions
• MME - HSS interface (S6a) and signaling with the use of Diameter
• S-CSCF - HSS interface (Cx) and signaling with the use of Diameter

Policy and Charging Control in EPS and IMS

• IP Connectivity Access Networks (IP-CANs) relation to PCC
• IP-CAN bearer establishment procedure
• IMS based charging principles (PCC rules and high level PCC operation)
• PCC nodes and functions (PCRF, PCEF, AF and SPR)
• QoS handling and authorization (filtering of user data and gating)
• QoS parameter mapping and management functions
• User plane handling in the PCEF
• Charging architecture (including CDR)
• Online, offline and roaming charging

EPC Interworking with Other Networks

• Inter-working with 3GPP and non-3GPP networks
• S3 interface and protocol stack (MME and SGSN)
• S4 interface and protocol stack (SGW and SGSN)
• Example interworking procedures (handover between LTE and UMTS, ISR concept and operation)
• Roaming scenarios (local breakout and home routed access)
• Interworking security considerations (example of untrusted non-3GPP access)
• Access Network Discovery and Selection Function (ANDSF) functionality and operation