5G Core Networks Course Core & IMS Learning © 2021 C2 General Introduction to 5G | The Reason behind 5G deployment • eMBB • URLLC • mMTC C2 General 2 4G & 5G IMT Standards 4G 𝐈𝐌𝐓-Advanced 𝐈𝐌𝐓 Simplified technical difference between 4G & 5G 5G 𝐈𝐌𝐓-2020 1 Gbps Peak data Rate 20 Gbps 10 Mbps User Exp. Data rate 100 Mbps 10 ms Latency 1 ms 1x Spectrum efficiency 3x 400 km/h Mobility 500 km/h 𝕀𝕟𝕥𝕖𝕣𝕟𝕒𝕥𝕚𝕠𝕟𝕒𝕝 𝕄𝕠𝕓𝕚𝕝𝕖 𝕋𝕖𝕝𝕖-𝕔𝕠𝕞𝕞𝕦𝕟𝕚𝕔𝕒𝕥𝕚𝕠𝕟𝕤 C2 General 3 5G use cases requirements High eMBB URLLC mMTC C2 General • Peak data Rates • Area traffic capacity • Network efficiency • Mobility • Latency • Mobility • Connection density • Peak data rates • Connection density Medium Low • Mobility 4 5G standard & Deployment Timelines C2 General 5 General look about the 5G Network Structure C2 General Radio Access Network Core Network Data Network 5G Ran or NR 5G Core Network Internet Facebook AS 6 What is meant by 5G NR ? C2 General 7 5G Architecture SA vs NSA eMBB eMBB URLCC mMTC C2 General 8 Dual Connectivity high level concept in 5G C2 General 9 5G Deployment options Option 2: 1. Supports all 5G use cases 2. 3. 5G e2e capabilities Control & user plane handled by 5G Inter-RAT mobility between LTE/EPC & NR/5GC. Fallback between VoLTE & VONR 4. 5. C2 General 10 5G Deployment options User plane Control plane C2 General 11 5G Deployment options C2 General 12 5G Deployment options C2 General 13 5G Deployment options C2 General 14 Benefits of 5G SA vs NSA ✓ 5G NSA • High speed data rates to 5G Customers • Lower cost compared to SA C2 General ✓5G SA • Launching new 5G services such as smart cities & smart factories • 5G will be fully virtualized • Lower latency • Improved Security 15 Network Slicing: enabling customized connectivity & Service optimization in 5G C2 General 16 Network Slicing: S-NSSAI C2 General 8 Bits 24 Bits SST SD 17 Cloud Native in 5G Cloud Native refers to the design and architecture principles that leverage cloud computing concepts and technologies to build and deploy 5G network functions and services. 1. 2. 3. 4. C2 General Installed Application doesn’t depend on the HW. Divided Software Life cycle management Resilience 18 Traditional 5G Network vs Service Based Architecture Traditional 5G Architecture C2 General Service Based Architecture 19 Difference Between Traditional vs Service Based Architecture ❖ Traditional Architecture • • • • C2 General Nodes or Network Elements Physical Network Functions Unique Interfaces & Protocols Not Flexible ❖ Service Based Architecture • • • • Network Functions Cloud Native and Virtual Networks Web Based interfaces Flexible 20 SBA-Service Based Architecture C2 General 21 Service Producer & Service Consumer C2 General 22 Interface between NF’s HTTP Rest: Hyper text transfer protocol representational state • • • • Get → Retrieve information from another NF Post → Send data to create a new resource or perform an action Put → Update or replace an existing resource with new data Delete → Request the removal of a resource AMF NRF PCF Service Registration HTTP Put PCF Information Information stored HTTP Response (Acknowledge) Service Discovery HTTP Get (Query for a PCF offering a certain service) Searching for NF’s meeting the request HTTP response ( list of the PCF’s offering this service) Service Request HTTP Get UE Information Determines the policy HTTP Response (Policy Info.) C2 General 23 Service Based Architecture NRF NEF NSSF UDR UDM PCF AF Service Based Interface Control Plane SMF AMF N4 N2 AUSF N1 5G RAN N3 N6 UPF C2 General Data Network User Plane 24 5G/NR - RAN Architecture C2 General 25 5G RAN splitting C2 General 26 gNB splitting to CU & DU CU (Central unit) • Centralized unit in the gNB. • Handling control plane functions. o C2 General o Managing Network resources o Establishing connections o Mobility Management DU (Distributed unit) • Data plane functions in gNB • • Data transmission and reception between users. Modulation, Coding & Radio Tx, Rx. Main role in Signaling and users connection 27 Benefits of CU & DU separation. 1. 2. 3. 4. C2 General Dynamic Resource Allocation Network Scalability Efficient Network Management Faster Software Upgrades and Maintenance 28 5G Core Architecture C2 General AMF “Access & Mobility Function” 5. 6. 7. 8. 9. UDR UDM PCF NRF NEF NSSF Service Based Interface SMF AMF AUSF Control Plane N1 Data Plane N3 N6 UPF C2 General AF N4 2. 3. 4. Interaction with gNB through N2 Interface, while N1 interface with the UE. A UE can connect to one AMF at a time. Passes all Signaling messages to the SMF. Relays all SMSs to SMF & Relays all location Info. Messages to LMF. Relays messages between UE and PCF. Authentication & Authorizations for UEs. Derives Cipher & Integrity keys. Interworking with 4G Networks. Stores 5G-GUTI N2 1. Data Network 30 UPF → User Plane function 1. 2. 3. 4. 5. UDR UDM PCF NRF NEF NSSF SMF AMF AUSF Control Plane N4 N1 Data Plane N3 N6 UPF C2 General AF Service Based Interface N2 6. Data Packets Forwarding Encapsulation & Decapsulation of data Traffic policing and shaping. Traffic calculation Data Buffering • Network congestion • QOS assurance • Adaptive Bitrate streaming GW for External Data Networks Data Network 31 SMF → Session Management function 1. 2. 3. 4. 5. 6. Setting up connectivity UE IP address allocation SMF has some functionality of SGW/PGW/MME UPF selection Retrieve policies for UE AUSF Downlink data notification for idle Ues. UDR UDM PCF NRF NEF NSSF AF Service Based Interface SMF AMF N4 N2 Control Plane N1 Data Plane N3 N6 UPF C2 General Data Network 32 NRF → Network Repository function • • • • Get → Retrieve information from another NF Post → Send data to create a new resource or perform an action Put → Update or replace an existing resource with new data Delete → Request the removal of a resource AMF NRF PCF Service Registration HTTP Put PCF Information Information stored HTTP Response (Acknowledge) Service Discovery HTTP Get (Query for a PCF offering a certain service) Searching for NF’s meeting the request HTTP response ( list of the PCF’s offering this service) Service Request HTTP Get UE Information Determines the policy HTTP Response (Policy Info.) C2 General 33 NSSF → Network Slice selection function 1. Selecting the set of Network Slice instance serving the UE. Slicing concept: • in 4G we uses the same Network for all the services available. • While 5G we use each service in a separate slice. 2. UDR UDM PCF NRF NEF NSSF AF Service Based Interface SMF AMF AUSF Control Plane N4 N2 5G 4G N1 eMBB Data Plane eMBB uRLLC mMTC mMTC N3 uRLLC C2 General N6 UPF Data Network 34 NSSF → Network Slice selection function 1. C2 General We differentiate between each slice using the NSSAI 8 Bits 24 Bits SST SD 35 NSSF → Network Slice selection function 1. 2. 3. Selecting the set of Network Slice instance serving the UE. Selects also the set of AMFs serving UE. AMF may be dedicated to more than one AMF. C2 General 36 NEF → Network Exposure Function 1. 2. Has no equivalent in 4G Network. Expose 5G Operators APIs for application developers. UDR UDM PCF NRF NEF NSSF AF Service Based Interface SMF AMF AUSF N4 N2 Control Plane N1 Data Plane N3 N6 UPF C2 General Data Network 37 UDM → Unified Data Management • UDR UDM PCF NRF NEF NSSF AF Similar to the HSS Home Subscriber Server. o o o o o Front end for UDR, uses UDR for Registration Management. Users authentication UE Service subscriptions Stores which AMF serves the user. Converts from SUCI to SUPI. Service Based Interface SMF AMF AUSF N4 N2 Control Plane N1 Data Plane N3 N6 UPF C2 General Data Network 38 UDR → Unified Data Repository function o o UDR UDM PCF NRF NEF NSSF AF Service Based Interface Stores all users related information’s. Data stored by UDR is offered to other NFs like UDM, PCF. SMF AMF AUSF N4 N2 Control Plane N1 Data Plane N3 N6 UPF C2 General Data Network 39 AUSF → Authentication server function • AUSF Handles UE Authentications. UDR UDM PCF NRF NEF NSSF AF Service Based Interface • EIR Check UE Handsets. SMF AMF AUSF N4 N2 Control Plane N1 Data Plane N3 N6 UPF C2 General Data Network 40 PCF → Policy Control function • Provides Policy control for Session management related functionality. • Interacts with other NFs. • Provisioning policies to UE. • Frequency selection priority. UDR UDM PCF NRF NEF NSSF AF Service Based Interface SMF AMF AUSF N4 N2 Control Plane N1 Data Plane N3 N6 UPF C2 General Data Network 41 UE States C2 General UE States in AMF UE- Registration Management states • RM-Registered: When UE is successfully registered to the Network. • RM-De-Registered: when is UE is powered off. C2 General 43 UE States in AMF UE- Connection Management states • CM-Idle: When UE Signaling Connection released & N2 is released. • CM-Connected: when UE signaling connection & N2 established. C2 General 44 UE States in AMF UE- RRC states C2 General • RRC Connected • RRC Inactive • RRC Idle 45 UPF & UE Continuity options C2 General SSC Modes in 5G • SSC Mode1 o • SSC Mode2 o o • No change in UPF PSA & UE IP address Change in connected UPF with change in IP Address. Break before Make SSC Mode3 o o C2 General Change in UPF & IP address. Make before break. 47 SSC Modes in 5G N3 • UPF2 Network Wide Mobility N9 • Breakout of Selected data flows N3 UPF1 Data Network C2 General 48 5G QOS C2 General S1-MME HSS MME S6a 5G QoS 4G QOS S11 SGW • • • It enables assigning fine-grained QOS policies to data flows through QOS flow management. Radio Bearer Data Network S5 S1-U S1 Bearer PGW S/S8 Bearer External Bearer E-RAB QOS profiles define treatment such as priority, latency & jitter. EPS Bearer End to End Service Bearer Each data flow is identified by a QoS flow ID. 5G QOS N3 N6 UPF Radio Bearer N3 Tunnel End to End Service Bearer C2 General Data Network External Bearer 50 5G QoS C2 General 51 5G Interfaces C2 General N13 AUSF 5G Interfaces N15 N8 Connection setup/release Handover preparation process Contexts transfer Paging RAN information reporting N5 N10 NSSF N7 N11 N2 interface gNB → AMF o o o o o N12 Registration De-Registration PDU Session Establishment/Modification/Release Service Request Mobility Procedures N1 PCF AMF SMF NEF N2 N14 UPF N3 N9 C2 General AF N22 o o o o o • UDM N1 Interface UE → AMF N4 • N6 Data Network 53 N13 AUSF 5G Interfaces N15 N8 N12 Data transfer GTP-U Protocol NSSF N7 N9 interface UPF → UPF N1 AMF • N14 interface AMF → AMF o o o Handover of UE contexts Location update Sharing of subscriber information's NEF N2 N14 UPF N3 N9 C2 General PCF SMF N4 Internetwork communications GTP-U Protocol QoS handling N11 o o o AF N5 N10 o o • UDM N3 Interface gNB → UPF N22 • N6 Data Network 54 N13 AUSF 5G Interfaces N15 N8 UDM N11 Interface AMF → SMF o N12 • Session establishment/Modification/Release N4 interface SMF → UPF PDU Session establishment/Modification/Release Policy enforcement Traffic steering & Routing Charging & usage reporting N7 N11 o o o o PCF N22 • N5 N10 NSSF AF N1 SMF • N15 interface AMF → PCF o N4 AMF NEF N2 QoS requirements N14 UPF N3 N9 C2 General N6 Data Network 55 N13 AUSF 5G Interfaces N15 N8 UDM N6 Interface UPF → DN o N12 • Data transfer to external Networks N7 interface SMF → PCF N7 Policy decisions Usage reporting Event triggers N11 o o o PCF N22 • N5 N10 NSSF AF N1 SMF • N10 interface SMF → UDM o o Retrieval of subscriber data Notifications of changes N4 AMF N14 UPF N3 N9 C2 General NEF N2 N6 Data Network 56 N13 AUSF 5G Interfaces N15 N8 UDM N8 Interface AMF → UDM Retrieval of subscriber data Authentication data Request Notifications of users location NSSF AF N5 N10 o o o N12 • N22 interface AMF → NSSF o Slice selection request N11 • PCF N22 N7 N1 SMF N4 AMF • N12 interface AMF → AUSF o • Authentication vectors alignment N12 interface UDM → AUSF N14 UPF N3 N9 C2 General NEF N2 N6 Data Network 57 NF Services C2 General Services offered by AMF N15 N8 • Namf_communication UDM N10 Allow other NFs communication with UE & gNB • Namf_MT • Namf_EventExposure o C2 General N1 AMF Other NFs can subscribe to mobility services. • Namf_Location o N7 To make sure UE is reachable for other NFs N11 o Other NFs can request UE location. SMF N2 N6 UPF N3 PCF N4 o Data Network 59 Services offered by AMF • Namf_communication o UEContextTransfer AMF2 5G Core AMF1 C2 General 60 Services offered by AMF • Namf_EventExposure o Subscribe UDM N1 AMF N2 C2 General 61 Services offered by AMF • Namf_MT o EnableUEReachability SMSF CM_Idle N1 AMF Paging Request Paging Response N2 C2 General 62 Services offered by AMF • Namf_Location o ProvidePositioningInfo Request Response LMF N2 CM_Idle N1 AMF C2 General 63 Services offered by SMF NEF • Nsmf_PDUSession o o Responsible for Handling the PDU sessions between UE & Network. It involves: Establishment, Release & Modify PCF AMF SMF Browse a website Nsmf_PDU Session Nsmf_PDUSession AF • Nsmf_EventExposure o It enables AF to subscribe to specific events within the SMF, such as changes in access type or SMF selection UPF • Nsmf_NIDD o C2 General NIDD" stands for Non-IP Data Delivery, and this service is dedicated to managing the delivery of non-IP data between the UE and DN (Data Network). 64 Services offered by PCF Npcf_AMPolicyControl o This service provides policies that manage the life cycle of PDU sessions. From establishing a session to modifying or terminating it N10 N1 AMF PCF SMF This service controls the policies related to Background data transfer(BDT) to NEF. N2 Npcf_UEPolicyControl o • N7 Npcf_BDTPolicyControl o • Its main role here is to authorize policies related to traffic routing, quality of service, and resources allocation. Npcf_SMPolicyControl o • AF Npcf_PolicyAuthorization o • UDM N4 • N8 This service deals with policies related to mobility management and access N11 • N15 This service provides policies specifically tailored to the behavior of user equipment (UE). UPF NEF N3 Npcf_EventExposure o C2 General This service allows for the exposure of certain policy events to external entities or applications. 65 Services offered by UDM Nudm_UEContextManagement N8 o used for UE context management and allow NFs like the AMF, SMF and SMSF to register and deregister with UDM and can provide the NFs with information related to UE’s e.g., a UE’s serving NF identifier, UE status, etc . • Nudm_SubscriberDataManagement N7 Nudm_UEAuthentication N11 o used to manage subscription data and enables NFs like AMF and SMF to retrieve user subscription data and allows the UDM to provided updates of subscriber data • N1 AMF o provides authentication subscriber data to the e.g., AMF • Nudm_ParameterProvision o service is used to provision information which can be used for the UE in 5GS AF N10 UDM PCF SMF N4 • N15 N2 UPF NEF N3 • Npcf_EventExposure o service allows NFs to subscribe to events and can provides monitoring indication of the events to the subscribed NF consumer C2 General 66 5G Identifiers C2 General 5G Identifiers Identities are used for accurate, secure & efficient communication between UE and the 5G Network. Those identities are used mainly for Authentication, Location management, Signaling & service continuity. • SUPI → subscription permanent identity o Unique per user o Stored in the UDM/UDR o Similar to IMSI o Consists of MCC, MNC & MSIN. o Has high security • SUCI → Subscription concealed identity o Used for SUPI protection o A one time used identifier o Network Generates SUPI using the SUCI • PEI → permanent equipment identifier o Each UE has a PEI o Similar to IMEI & IMEI SV o Used by EIR to classify users devices C2 General 68 5G Identifiers Identities are used for accurate, secure & efficient communication between UE and the 5G Network. Those identities are used mainly for Authentication, Location management, Signaling & service continuity. • 5G-GUTI → Globally unique temporary identifier o Temporary identifier to protect users privacy o Generated by AMF o Temporary used by UE till next initial registration. o Consists of GUAMI & 5G-TMSI C2 General 69 Mapping of 5G-GUTI to 4G-GUTI In the beginning days of 5G, 4G will be existing widely with low coverage of 5G. UE will register either to 5G or 4G. UE will switch between 4G & 5G, and network will assist in this transition. C2 General 70 Bridging 4G & 5G: Seamless connectivity C2 General Bridging 4G & 5G: Seamless connectivity EPC 5GC UDICOM HSS UDM PCF N7 N8 N26 SGW AMF N11 SMF N4 UPF SGW N3 C2 General N1 S1-U S5-U Data Network 72 5G Call flows C2 General 5G call flows 5G call flows provide a detailed sequential representation of the signaling and data exchange between 5G network components during various procedures, such as registration, session establishment, and mobility. Understanding these call flows is crucial for network engineers and professionals to optimize, troubleshoot, and ensure seamless communication within the 5G architecture. • Security in 5G • Registration call flow • De-Registration procedures • UE Triggered service Request • Network Triggered Service Request • Service continuity call flow between 4G & 5G. C2 General 74 Security in 5G New entities are being added in 5G which supports in 5G Security. • ARPF → Authentication Repository & Processing Function o Located inside the UDM o Stores user credential: Key & SUPI o Supports Authentication: Generates Authentication vectors o Located inside the HPLMN • AUSF → Authentication Server Function o A Standalone NF o Located in HPLMN UE SIM AMF UDM SEAF ARPF SIDF • SEAF → Security Anchor Function o Entity inside AMF o Located in HPLMN/VPLMN o Handles authentication in VPLMN • SIDF → Subscription Identifier De-Concealing Function C2 General o Converts SUCI to SUPI o Located in HPLMN 75 Security in 5G C2 General 76 Authentication Procedures AMF 1 UDM AUSF (SEAF) (ARPF) NAS Registration Request 2 SUCI or 5G-GUTI Nausf_UEAuthentication_Authenticate Request 3 SUCI or 5G-GUTI Nudm_UEAuthentication_Get Request SUCI or 5G-GUTI 5 4 Generates AUTN,RAND,XRES,CK,IK Nudm_UEAuthentication_Get Response AUTN,XRES,KAUSF,SUPI 6 Stores XRes & Computes a HXRes Nausf_UEAuthentication_Authenticate Response AUTN, HXRes,RAND 7 Stores HXRes Authentication Request 8 RAND,AUTN Computes Res,CK,IK,KAUSF,KSEAF,KAMF Authentication Response Res 9 Verifies HXRes Nausf_UEAuthentication_Authenticate Response Res C2 General Verifies Res Nausf_UEAuthentication_Authenticate Response KSEAF, SUPI 77 Registration Call flow AMF AMF (New) (Old) SMF PCF AUSF UDM Registration Request SUCI or 5G-GUTI 1 AMF Selection Registration Request SUCI or 5G-GUTI Namf_Communications_UEContextTransfer 2 Namf_Communications_UEContextTransferResponse Authentication and Security Process 3 Namf_Communications_UEContextTransferComplete 4 Nudm_UECM_Registration Nudm_SDM_Get Nudm_SDM_Subscribe 5 Nudm_UECM_DeregistrationNotify Nudm_SDM_Unsubscribe Npcf_AMPolicyControl_Create 6 Npcf_AMPolicyControl_Create Nsmf_PDUSession_UpdateSMContext 7 8 C2 General Nsmf_PDUSession_ReleaseSMContext Registration Accept Registration Complete 78 Periodic Registration Purpose: • • Reachability: Ensures the network knows where the UE is for delivering services. Refresh Security: The process can involve re-establishing security parameters between the UE and the network. Triggers: • Timer-based: Periodic registration can be triggered based on a specific timer (T3324) expiry. The network provides the value of this timer to the UE. AMF T3324 Timer expires Registration Request Registration Request Process Flow: • • • • • Benefits: • • C2 General The UE monitors the periodic registration timer (T3324). When the timer expires, the UE initiates the registration procedure with the network. The UE sends a Registration Request message to the network. The network processes the request and responds with a Registration Accept or Reject message. If accepted, the network updates the UE's context and might provide a new T3324 value for the next periodic registration. Battery Life: Periodic registration ensures that the UE doesn't need to communicate with the network frequently, which can help in saving battery life. Network Efficiency: By knowing the active UEs and their locations, the network can manage resources more efficiently. Authentication (If needed) Registration Accept/Reject Registration Complete 79 De-Registration Call flow AMF SMF PCF UPF UDM De-Registration Request 1 De-Registration Request Nsmf_PDUSession_ReleaseSMContextRequest N4 Session release Request 2 N4 Session release Response Nsmf_PDUSession_ReleaseSMContextResponse Npcf_SMPolicyControl_Delete 3 Npcf_SMPolicyControl_Delete Nudm_SDM_Unsubscribe 4 Nudm_UECM_Deregistration Npcf_AMPolicyControl_Delete 5 6 C2 General Npcf_AMPolicyControl_Delete De-Registration Accept Signaling Release 80 UE triggered Service Request AMF SMF PCF UPF UDM Service Request 1 Service Request Authentication and Security Process 2 Nsmf_PDUSession_UpdateSMContextRequest 3 Nsmf_PDUSession_UpdateSMContextResponse Service Accept Setting up RAN resources 4 Uplink Data N2 ACK Nsmf_PDUSession_UpdateSMContextRequest Npcf_SMPolicyControl_Update 5 N4 Session Modification Downlink Data C2 General Nsmf_PDUSession_UpdateSMContextResponse 81 Network triggered Service Request C2 General 82
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