EPC Protocols and Procedures

Subject: 4G LTE
Category: Core
Duration: 3 days

Course outline:

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

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

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