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EPC Network Fundamental www.huawei.com



Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.



References 3GPP TS23401 R8



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Page1



Objectives Upon completion of this course, you will be able to: Describe the EPC network structure Describe the EPC Network interface and protocol Describe the EPC Network working procedures



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Page2



Contents 1. EPC Network Structure 2. EPC Network Working Principle



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Page3



Contents 1. EPC Network Structure 2. EPC Network Working Principle



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Page4



Contents 1. EPC Network Structure 1.1 EPC Network Structure 1.2 EPC Network Interfaces



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Page5



3GPP System Evolution 3GPP



GSM/ GPRS



UMTS: R99/R4/R5/R6/R 7



1.PS core network only support nonreal time services. 2. Voice services are carried in the CS domain. 3. Low efficiency of routes in forwarding data due to the over-layered networks. 4. Incapability of supporting multiple radio access systems



LTE/EPC: R8/R9/R10



1. The all-IP network contains the PS. Voice services are jointly provided by the PS and the IP Multimedia Subsystem (IMS). 2. Flattened network architecture. 3. Support of the multiple access technologies. 4. High data transmission rate: downlink 100 Mbit/s and uplink traffic 50 Mbit/s.



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Page6



The Evolution of PS Network



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Page7



EPS Network Structure Control plane



PCRF



HSS eNodeB



User plane MME S1-MME S6a



LTE -Uu



X2



S1-U



UE



LTE



Gx



S11



S1-MME eNodeB



Rx



Gxc



S1-U



S5



S-GW



SGi P-GW



SAE



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Page8



Operator's IP Service



EPS Network Functions The EPS network perform the following logical functions : Network Access Control Functions. Packet Routeing and Transfer Functions. Mobility Management Functions. Security Functions. Radio Resource Management Functions. Network Management Functions.



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Page9



GUL Network Structure Co-Site of the S-GW and P-GW UTRAN NodeB



SGSN S12



RNC



GERAN



S6a



S3



PCRF HSS



BTS



BSC/PCU MME S11



S4 Gx



Rx



S1-MME



LTE eNodeB



S1-U



SGi S-GW/P-GW



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Page10



Operator's IP Services



GUL Network Structure Separate Installation of the S-GW and P-GW



UTRAN



SGSN S12



RNC



NodeB



S3



GERAN



PCRF



S6a HSS



BTS



BSC/PCU



S4



MME S1-MME



LTE eNodeB



Gx



S11



S1-U



S5 S-GW



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Rx



SGi P-GW



Page11



Operator's IP Services



Functions of EPC Network Entity MME: mobility management entity Non-access stratum (NAS) signaling



MME selection for handovers with MME change



NAS signaling security



SGSN selection for handovers to 2G/3G access networks



Signaling interaction between core network (CN) Roaming nodes during an inter–3GPP access network handover Reachability of UEs in IDLE mode



Authentication



Tracking area (TA) list management



Bearer management



Selection of the P-GW and S-GW



Lawful interception of signaling traffic



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Page12



Functions of EPC Network Entity SGW: serving gateway Functioning as the local mobility anchor point for inter-eNodeB handovers



Assisting the eNodeB reordering function during inter-eNodeB handovers by sending one or more "end marker" packets to the source eNodeB immediately after switching the path Supporting inter-operator charging based on subscriber and QoS class identifier (QCI) granularity Implementing downlink packet buffering and E-UTRAN triggered paging in ECM-IDLE mode



Functioning as the mobility anchor point for



Supporting packet routing and transfer



inter-3GPP handovers Performing lawful interception



Supporting transport level packet marking for uplink and downlink data



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Page13



Functions of EPC Network Entity P-GW: packet data network gateway Packet filtering based on single user



Uplink and downlink gateway control based on traffic



Lawful interception



Uplink and downlink rate control based on traffic



IP address allocation for UEs



Uplink and downlink rate enforcement based on access point name-aggregate maximum bit rate (APN-AMBR)



Supporting packet marking for uplink and



Downlink rate enforcement based on



downlink data based on transfer priority



guaranteed bit rate (GBR)



Uplink and downlink charging based on traffic



DHCPv4 (server/client) and DHCPv6 (server) functions



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Page14



Functions of EPC Network Entity HSS: home subscriber server Supporting authentication and registration for subscribers and downloading user profiles to the MME Supporting authentication and registration for non-3GPP subscribers and distributing user profiles to the AAA Providing roaming restriction Providing barring services Providing restrictions over access network types Implementing IPv4/IPv6 dual protocol stack Supporting Diameter-based IP networking



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Page15



Functions of EPC Network Entity PCRF: policy control and charging rule function The PCRF is mainly used for prescribing rules for policy and charging control. The PCRF is responsible for terminating the Rx interface and the Gx interface.



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Page16



HUAWEI LTE-EPC Solution HSS



SGSN GPRS



Control plane User plane BTS



BSC/PCU PCRF



UMTS NodeB



RNC



MME



Operator Service Network



LTE S-GW



eNodeB



P-GW



CDMA BTS



BSC/PCF



PDSN/HSGW



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Page17



Corporate Services



Contents 1. EPC Network Structure 1.1 EPC Network Structure 1.2 EPC Network Interfaces



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Page18



EPC Network Interfaces Control plane



PCRF



HSS eNodeB



User plane MME S1-MME S6a



LTE -Uu



X2



S1-U



UE



LTE



Gx



S11



S1-MME eNodeB



Rx



Gxc



S1-U



S5



S-GW



SGi P-GW



SAE



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Page19



Operator's IP Service



Control Plane Protocol Stacks NAS



NAS RRC



RRC



S1-AP



S1-AP



PDCP



PDCP



SCTP



SCTP



RLC



RLC



IP



IP



MAC



MAC



L2



L2



L1



L1



L1



L1



UE



LTE-Uu



eNodeB



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S1-MME



Page20



MME



User Plane Protocol Stacks Application IP



IP Relay



Relay



PDCP



GTP-U



GTP-U GTP-U



PDCP



GTP-U



RLC



RLC



UDP/IP



UDP/IP



UDP/IP



UDP/IP



MAC



MAC



L2



L2



L2



L2



L1



L1



L1



L1



L1



L1



LTE-Uu



UE



S1-U



eNodeB



S5/S8 a



Serving GW



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SGi



PDN GW



Page21



S1 Interface S1-MME



MME



S1-U S-GW



eNodeB



S1-AP



S1-AP



SCTP



SCTP



GTP-U



GTP-U



UDP/IP



UDP/IP



IP



IP



L2



L2



L2



L2



L1



L1



L1



L1



eNodeB



S1-MME



MME



eNodeB



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S1-U



Page22



S-GW



S6a Interface S1-MME



S6a



HSS



MME



eNodeB



Diameter



Diameter



SCTP



SCTP



IP



IP



L2



L2



L1



L1 S6a



MME



HSS



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Page23



S10 Interface S10 MME S1-MME



S6a



HSS



MME



eNodeB GTP-C



GTP-C



UDP



UDP



IP



IP



L2



L2



L1



L1 S10



MME



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MME



Page24



S11 Interface S10 MME S1-MME



MME



eNodeB GTP-C



GTP-C



UDP



UDP



IP



IP



L2



L2



L1



L1 S11



MME



S6a S11



S-GW



S-GW



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Page25



HSS



S5/S8 Interface



MME



S11



S1-U



eNodeB PLMN1



S5



S-GW



S8



P-GW



PLMN2 P-GW



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Page26



S5/S8 Interface: 3gpp 23401 3GPP23.401(3gpp access): An S5/S8 interface based on GTP. The signaling plane runs the GTPv2 protocol and the user plane runs the GTPv1 protocol. GTP-C



GTP-C



GTP-U



GTP-U



UDP/IP



UDP/IP



UDP/IP



UDP/IP



L2



L2



L2



L2



L1



L1



L1



L1



P-GW



S-GW



S-GW



GTP based S5/S8



Control plane Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.



GTP based S5/S8



User plane Page27



P-GW



Gx/Gxc Interface



PCRF Gxc



S-GW



Gx



Diameter protocol application



Diameter protocol application



Diameter base protocol



Diameter base protocol



TCP



TCP



IP



IP



L2/L1



L2/L1



P-GW



PGW/SGW



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Gx/Gxc



Page28



PCRF



SGi Interface AAA Server SGi



P-GW



Web Server PDN



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Page29



Contents 1. EPC Network Structure 2. EPC Network Working Principle



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Page30



Contents 2. EPC Network Working Principle 2.1 General Service Process 2.2 Identity of EPC Network 2.3 Mobility Management Procedure 2.4 Session Management Procedure



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Page31



Typical Packet Service



MME



1



ICP/ISP internet



eNodeB



2



S-GW



P-GW Signaling Data



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Page32



Typical Voice Service IMS domain EPC Signaling IMS Signaling SS7 Signaling Data (VOIP)



MGCF 3



CSCF



IMS-MGW 4



MME



1



SS7



2 MSC eNodeB



4



S-GW



PLMN



P-GW EPC



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Page33



Roaming: Home Routed VPLMN Gb



HPLMN HSS



SGSN



PCRF



GERAN Iu S3



S4 S6a



Gx



Rx



S12 UTRAN S11 S1-C



MME



S8



SGi



S1-U E-UTRUAN



S-GW



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PDN-GW



Page34



Operator’s IP Service



Roaming: Local Breakout VPLMN Gb



HPLMN



SGSN



HSS



H-PCRF Rx



GERAN Iu S3



S4



Operator’s IP Service



S9



S6a V-PCRF



S12 UTRAN S11 S1-C



Gx



MME



S5



SGi



S1-U E-UTRUAN



S-GW



Operator’s IP Service



PDN-GW



Local Breakout with Home Operator's Application Functions only



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Page35



Roaming: Local Breakout VPLMN Gb



HPLMN



SGSN



HSS



H-PCRF



Operator’s IP Service



GERAN Iu S3



S4



S9



S6a V-PCRF



S12



Rx



UTRAN S11 S1-C



Gx



MME



S5



SGi



S1-U E-UTRUAN



S-GW



Operator’s IP Service



PDN-GW



Local Breakout with Visited Operator's Application Functions only



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Page36



Contents 2. EPC Network Working Principle 2.1 General Service Process 2.2 Identity of EPC Network 2.3 Mobility Management Procedure 2.4 Session Management Procedure



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Page37



Identity of EPC Network MME



MMEI= MME Group ID+MME Code



TAI=MCC+MNC+TAC TA List



TA List



TA 1



TA 2



TA 1



TA 2



CELL1 CELL2



CELL3 CELL4



CELL1 CELL2



CELL3 CELL4



IMSI MSISDN GUTI=GUMMEI+M-TMSI =MCC+MNC+MMEI+M-TMSI Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.



Page38



Contents 2. EPC Network Working Principle 2.1 General Service Process 2.2 Identity of EPC Network 2.3 Mobility Management Procedure 2.4 Session Management Procedure



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Page39



Subscriber State Management Subscriber state EMM: EPS Mobility Management EMM-DEREGISTERED EMM-REGISTERED



ECM: EPS Connection Management ECM-IDLE ECM-CONNECTED



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Page40



EMM State Detach, Attach Reject, TAU reject, E-UTRAN interface switched off due to Non-3GPP handover, All bearers deactivated EMM-DEREGISTERED



EMM state in UE



EMM-REGISTERED Attach accept



Detach, Attach Reject, TAU reject, All bearers deactivated EMM-DEREGISTERED



EMM state in MME



EMM-REGISTERED Attach accept TAU accept for a UE selecting E-UTRAN from GERAN/UTRAN



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Page41



ECM State RRC connection released ECM-CONNECTED



ECM-IDLE



ECM state in UE



RRC connection established



S1 connection released ECM-CONNECTED



ECM-IDLE S1 connection established



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Page42



ECM state in MME



MM and EPS Bearer Context MM context MME



Subscription information



HSS



EPS bearer context



EPS bearer Subscription context



ICP/ISP internet MM context



S-GW



P-GW



EPS bearer context



EPS bearer context



EPS bearer context



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Page43



Signaling Data



Mobility Management Procedures Main mobility management procedures: Attach procedure Tracking area update procedure Detach procedure



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Page44



Attach Procedure Function of attach procedure: The UE register to the EPS network. The always-on IP connectivity for UE/users of the EPS is enabled by establishing a default EPS bearer during Network Attachment. The MM context and EPS bearer context will be created in the MME and UE. The EPS bearer context will be created in S-GW and P-GW.



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Page45



Attach Procedure eNodeB



New MME Old MME



HSS



S-GW



P-GW



1. Attach request 2. Identification req/rsp 3. Identity req/rsp 4. Security function 5. Update location request 6. Cancel location /Ack 7. Update location Ack 8. Create default bearer req 9. Create default bearer req 10. Create default bearer rsp



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Page46



Attach Procedure eNodeB



New MME Old MME



HSS



S-GW



11. Create default bearer rsp 12. Attach accept 13. Radio bearer establish 14. Attach complete 15. Update bearer request 16. Update bearer response 17. Uplink and downlink data



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Page47



P-GW



Location Information Storage HSS



MME1



MME IP address



MME2



Tracking Area list Tracking Area ID E-UTRAN Cell Global Identity



Tracking Area list Tracking Area ID



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Page48



TAU Procedure S-GW2



S-GW1



MME2



MME1



TA list 1



TA list 2



Periodic TAU



MME3



TA list 4



TA list 3



Inter MME TAU with SGW change



Intra MME TAU



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Inter MME TAU without SGW change



Page49



Inter TAU without SGW change eNodeB



New MME Old MME



HSS



S-GW



P-GW



1. TAU request 2. Context request 3. Context response 4. Security function 5. Context Ack 6. Update bearer request 7. Update bearer request 8. Update bearer response 9. Update bearer response



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Page50



Inter TAU without SGW change eNodeB



New MME Old MME



HSS



S-GW



10. Update location request 11. Cancel location 12. Cancel location Ack 13. Update location Ack 14. TAU accept 15. TAU complete



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Page51



P-GW



Inter TAU with SGW change eNodeB



New MME Old MME



HSS New S-GW Old S-GW



P-GW



1. TAU request 2. Context request 3. Context response 4. Security function 5. Context Ack 6. Create bearer request 7. Update bearer request 8. Update bearer response 9. Create bearer response



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Page52



Inter TAU with SGW change eNodeB



New MME Old MME



HSS New S-GW Old S-GW



10. Update location request 11. Cancel location 12. Cancel location Ack 13. Update location Ack 16. TAU accept 17. TAU complete



14. Delete bearer request 15. Delete bearer response



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Page53



P-GW



Detach Procedure The detach procedure is used in the following scenarios: A UE is detached from the EPS service. A UE is disconnected from the last PDN connection. The network informs a UE that the UE cannot access to the EPS.



A UE can be detached explicitly or implicitly. Explicit detach Implicit detach



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Page54



UE Initiated Detach Procedure eNodeB



MME



S-GW



P-GW



1. Detach request 2. Delete bearer request 3. Delete bearer request 4. Delete bearer response 5. Delete bearer response 6. Detach accept 7. Signaling connection release



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Page55



Security Function 2G



3G



EPC



Authentication



Single-directional authentication



bi-directional authentication



bi-directional authentication



Security vectors



Triplet (RAND, Sres, and Kc)



Quintet (RAND, XRES, CK, IK, and AUTN)



New EPS security vectors (RAND, AUTN, XRES, and KASME). The UMTS and EPS authentication vectors are separated.



Integrity protection



No



Yes



Yes



SIM compatibility



N/A



Yes



No



Layered security architecture



No



No



Provides protection for the NAS layer and the AS layer separately. Manages the keys in the NAS and AS layers separately. Performs the algorithm negotiation for the NAS and AS layers separately.



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Page56



Authentication Vector EPS authentication quaternary RAND: Random Challenge AUTN: Authentication Token XRES: Expected Response Kasme: Ciphering key



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Page57



Authentication Procedure MME



HSS



1. Authentication data request 2. Authentication data response 3. User authentication request 4. User authentication response



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Page58



EPS Security Architecture UE



MME NAS



Ciphering/integrity



NAS



NAS eNodeB



RRC



RRC Ciphering/integrity



RRC



UP Ciphering PDCP



PDCP



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Page59



NAS/AS Security Mode Procedure eNodeB



MME



1. NAS security mode command 2. NAS security mode complete



1. AS security mode command 2. AS security mode complete



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Page60



Contents 2. EPC Network Working Principle 2.1 General Service Process 2.2 Identity of EPC Network 2.3 Mobility Management Procedure 2.4 Session Management Procedure



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Page61



Multiple-PDN connectivity Server



PDN connection 1: APN1



Intranet P-GW ICP/ISP



S-GW



internet



PDN connection 2: APN2 P-GW PDN connection 3: APN3



Server Intranet S-GW



P-GW



Wap server



PDN connection 4: APN4



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Page62



Wap network



EPS Bearer One PDN connection include one default EPS bearer, and zero or several dedicated EPS bearer. PDN connection 1 Default EPS bearer Dedicated EPS bearer 1 Dedicated EPS bearer 2 P-GW



S-GW EPS bearer



Radio bearer



eNodeB



S1 bearer



S-GW S5/S8 bearer



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Page63



P-GW



Session Management Procedure EPS bearer management procedure Bearer activation procedure Bearer modification procedure Bearer deactivation procedure



PDN connection management procedure (UE support for multiple PDN connections): UE requested PDN connectivity procedure UE or MME requested PDN disconnection procedure



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Page64



P-GW Initiated Dedicated Bearer Activation eNodeB



MME



S-GW



P-GW



1. Create dedicated bearer request 2. Create dedicated bearer request 3. Session management request 4. Creation of bearer of E-UTRAN 5. Session management response 6. Create dedicated bearer response 7. Create dedicated bearer response



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Page65



P-GW Initiated Bearer Modification With QoS Update eNodeB



MME



S-GW



P-GW



1. Update bearer request 2. Update bearer request 3. Session management request 4. Update of bearer of E-UTRAN 5. Session management response 6. Update bearer response 7. Update bearer response



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Page66



PDN GW Initiated Bearer Deactivation eNodeB



MME



S-GW



P-GW



1. Delete bearer request 2. Delete bearer request 3. Deactivate EPS bearer context request 4. Release of bearer of E-UTRAN 5. Deactivate EPS bearer context accept 6. Delete bearer response 7. Delete bearer response



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Page67



UE Requested Bearer Resource Modification eNodeB



MME



S-GW



P-GW



1. Request bearer resource modification 2. Request bearer resource modification 3. Request bearer resource modification



4. Dedicated bearer activation, or dedicated bearer modification, or dedicated bearer deactivation procedure



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Page68



UE Requested PDN Connectivity Procedure eNodeB



MME 1. PDN connectivity request



S-GW



P-GW



2. Create default bearer request 3. Create default bearer request 4. Create default bearer response 5. Create default bearer response 6. PDN connectivity accept 7. Creation of bearer of E-UTRAN 8. PDN connectivity complete 9. Update bearer request 10. Update bearer response Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.



Page69



UE Requested PDN Connectivity Procedure eNodeB



MME 1. PDN connectivity request



S-GW



P-GW



2. Create default bearer request 3. Create default bearer request 4. Create default bearer response 5. Create default bearer response 6. PDN connectivity accept 7. Creation of bearer of E-UTRAN 8. PDN connectivity complete 9. Update bearer request 10. Update bearer response Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.



Page70



UE Requested PDN Disconnection Procedure eNodeB



MME



S-GW



P-GW



1. PDN disconnection request 2. Delete bearer request 3. Delete bearer request 4. Delete bearer response 5. Delete bearer response 6. Release of bearer of E-UTRAN



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Page71



Summary The EPC network is composed of: MME, S-GW, P-GW



The main working principle of EPC network are: Mobility management procedure Session management procedure



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Page72



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