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Packet core network basics
The document outlines a training schedule for the PS core overview, detailing sessions on basic and advanced topics related to the packet core network from July to September 2017. It includes various subjects such as the functionalities of SGSN and GGSN, PDP context activation, and network architecture. Additionally, it discusses the evolution of the core network to Evolved Packet Core (EPC) and presents an automation script for managing CDR files in the GGSN environment.
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Packet core network basics
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- 2. Training Schedule #Week DayDate Duration Time Basic/Advance WK-01 Fri 14thJuly,2017 2Hours 11:00-13:00GMT+3 Basic WK-02 Fri 21stJuly,2017 2Hours 11:00-13:00GMT+3 Basic WK-03 Fri 28thJuly,2017 2Hours 11:00-13:00GMT+3 Basic WK-04 Fri 4thAug,2017 2Hours 11:00-13:00GMT+3 Advance WK-05 Fri 11thAug,2017 2Hours 11:00-13:00GMT+3 Advance WK-06 Fri 18thAug,2017 2Hours 11:00-13:00GMT+3 Advance WK-07 Fri 25thAug,2017 2Hours 11:00-13:00GMT+3 Basic WK-08 Fri 1stSep,2017 1Hour 11:00-13:00GMT+3 Advance WK-09 Fri 1stSep,2017 2Hours 11:00-13:00GMT+3 WK-10 Fri 8thSep,2017 2Hours 11:00-13:00GMT+3 Basic WK-11 Fri 15thSep,2017 2Hours 11:00-13:00GMT+3 Advance WK-12 Fri 22ndSep,2017 1Hour 11:00-13:00GMT+3 Advance WK-13 Fri 29thSep,217 1hours 11:00-13:00GMT+3 Subject/ Topics PacketCore NetworkBasics GatewayGPRSSupportNode GatewayGPRSSupportNode - Part03- PISC GatewayGPRSSupportNode - Part02 PS Core / EPC-Competence DevelopmentTraining -2017 PSCore Course - Exam IntroductionTo LTE EPC Network- Part03 ServingGPRSSupportNode - SGSN Course Exam SAPC Par02 IntroductionTo LTE EPC Network- Part01 IPWorks SAPC Part01 IntroductionTo LTE EPC Network- Part02
- 3. BasicGPRS NetworkArchitecture SGSN GGSN Gi(IP)Gn Gs Gb Gp Gr (MAP) IP Network Inter PLMN Backbone Network IP MSC/VLRBTS BSC HLR MAP MS RNCRAN node B Gp Iu
- 4. MS BTS BSC RNCNODE-BMS SGSNGGSN SGSN GGSN MSC SCP/Camel HLR OSS Corporate LAN Gs SMS Um Abis Gb Ge Gn GomGr Gn Gn Gn Gn Um Iub Iu Gi Gi Gd GSM WCDMA ISP PCRF ExtendedLogical Network Architecture
- 5. Functional view onGPRS Local area network Server Router Local area network Server Router Corporate 2 Corporate 1 Intra-PLMN backbone network (IP based) Serving GPRS Support Node (SGSN) Point-To- Multipoint Service Center (PTM SC) Gateway GPRS Support Node (GGSN) GPRS INFRASTRUCTURE HLR/AuC MSC BSCBTS Packet networkPSTN Packet networkSS7 Network Packet network Data network (Internet) Packet network Data network (X.25) Packet network Inter-PLMN Backbone network Border Gateway (BG) Gb Gr Gd Gi.IP Gi.X.25 Firewall Firewall Firewall Um R/S SMS-GMSC Gr Gd Gs Gs Gp Gn Gn EIR MAP-F
- 6. Protocol Level LogicalNetworkArchitecture
- 7. SGSN- Functionality SGSN –Serving GPRS Support Node SGSN handles the communication with MSs and the establishment of the connection between an MS and the PDN. Functionalities at a glance: •Serves MSs in SGSN area •Mobility Management functions, e.g •Update Location, Attach, Paging,.. •Security and access control: •Authentication, Cipher setting, IMEI Check... •Routing / Traffic-Management •Collecting charging data •Realises Interfaces: Gn, Gb, Gd, Gp, Gr, Gs, Gf •Controls subscribers in its service area (SLR) •Lawful Interception • Routing Area Update (Location Registration) • Location Update for CS • Attach / Detach • P-TMSI allocation / reallocation • Authentication • Paging (PS & CS) Mobility Management • PDP context activation • PDP context modification • PDP context cancellation Session Management Ericsson MKVI Huawei SGSN
- 8. GGSN- Functionality GGSN– GatewayGPRS Support Node SGSN handles the communication with MSs and the establishment of the connection between an MS and the PDN. Functionalities at a glance: •Acts as an interface and a router to external networks •It contains routing information for GPRS mobiles... •Tunnel packets through the IP based internal backbone •Collects charging data •Packet filter for incoming traffic •Packet inspection •Gateway with online charging system • PDP context activation • PDP context modification • PDP context cancellation Session Management M120 GGSN UGW9811 PGW
- 9. DNS- Functionality DNS– DomainName System DNS interface with SGSN to perform some very important functionality Functionalities at a glance: •Resolve the APN to a GGSN IP in the PDP active procedure •Resolve the RAI to a SGSN IP in the inter-SGSN RAU procedure •Resolve the RNCID to a SGSN IP in the relocation procedure (UMTS) IPWorks DNS on SUN HW
- 10. PCRF – Functionality PCRF–Policy and Charging Rule Function PCRF is a Policy Server. It provides Centralized Policy Management according to the 3GPP Policy and Charging Architecture Functionalities at a glance: •Service Authorization •Redirection •Bandwidth Management •Service Based Routing •Content Filtering •Charging •Control based on usage E// SAPCH// UPCC PCRF
- 11. Other Elements -Functionality BGW– Border Gateway Not defined within GPRS Network Functionalities at a glance: •Routes packets from SGSN/GGSN of one operator to a SGSN/GGSN of another operator. CGW– Charging Gateway Not defined within GPRS Network Functionalities at a glance: •Collects charging information from SGSNs and GGSNs
- 12. GPRSAttach •When a MSis turned on, the first function it performs is a GPRS attach •GSM access authentication (towards Home Network, HLR (Authentication Center - AuC)) •User profile is downloaded from HLR to the serving SGSN •When the GPRS attach is complete, the MS is physically connected to the visited network
- 13. AttachProcedure 1.Attach Request MS BSSNew SGSN Old SGSN GGSN EIR New MSC/VLR HLR old MSC/VLR 2. Identification Request 3. Identification Response 3. Identity Request 3. Identity Response 4. Authentication 5. IMEI check 6a. Update Location 6b. Cancel Location 6c. Cancel Location ACK 6d. Insert Subscriber Data 6d. Insert Subscriber Data ACK 6e. Update Location ACK 8. Attach Accept 9. Attach Complete 10. TMSI Reallocation complete 7c. Cancel Location 7d.ACK 7a. Location Update Request 7b. Update Location 7e. Insert Subscriber data 7h. Location Update Accept 7f. Insert Subscriber data ACK 7b. Update Location ACK
- 14. The Packet DataProtocol (PDP) Context •In order to be able to send and receive data, the mobile must set-up a packet data bearer •The PDP bearer is associated with contexts in each nodes that data are traversing. •The bearer is set-up via “PDP context activation” procedures •PDP context describes requirements of the connection to the packet networks: Type, network address, Access Point Name (APN), QoS, etc. •SGSN validates request against subscription information downloaded from HLR during GPRS Attach •Access point name sent to DNS, IP address(s) of suitable GGSNs returned •Logical connection using GPRS tunnels (GTP) between SGSN and GGSN •IP address allocated (GGSN pool, DHCP, RADIUS)
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- 16. Mobile Address Allocation GGSNAddress Pools Static, dynamic allocation at GPRS packet data activation HLR The HLR may keep a static IP address that is fetched by the SGSN at GPRS attach RADIUS The GGSN may interact with an external AAA server in order to perform AAA functions as well as dynamic IP address allocation at GPRS packet data activation DHCP server The GGSN may interact with an external DHCP server to perform dynamic IP address allocation at GPRS packet data activation
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- 18. Roaming Billing • TAP- Records (Transferred Account Procedure) – Existing methods of TAP exchanges shall be used – TAP File Spec 3 required - GPRS enhancements like: data volume, IP address, APN, etc. • Different concepts to existing TAP Record Procedures – Partial Records Generated + Data volume counts – CDRs from HGGSN and VSGSN - different records from different networks for the same connection.
- 19. 2G Mobility StateTransition PDUtransmission Implicit Detach or Cancel Location GPRS Attach READY timer expiry or Force to STANDBY GPRS Detach GPRS Attach PDU reception GPRS Detach or Cancel Location MM State Model of MS MM State Model of SGSN IDLE READY STANDBY IDLE READY STANDBY READY timer expiry or Force to STANDBY or Abnormal RLC condition
- 20. 3G Mobility StateTransition PMM- DETACHED PSAttach PS Signalling Connection Release PS Signalling Connection Establish PS Detach PMM- CONNECTEDPMM-IDLE Detach, PS Attach Reject, RAU Reject PMM- DETACHED PS Detach PMM- CONNECTED Serving RNC relocation 3G-SGSN MM StatesMS MM States SM-ACTIVE or INACTIVE SM-ACTIVE or INACTIVE SM-ACTIVE or INACTIVE SM-ACTIVE or INACTIVE Detach, PS Attach Reject, RAU RejectPS Attach PS Signalling Connection Establish PS Signalling Connection Release PMM-IDLE
- 21. Routing Area UpdateProcedure MS RAI2 RAI 4 SGSN SGSN RAI 1 RAI 3 cell Intra SGSN-RAU Inter SGSN -RAU Gn
- 22. Paging for GPRS(2G) 5. Any LLC Frame 4. Any LLC Frame 3. GPRS Paging Request 2. Paging Request 1. PDP PDU MS BSS SGSN STANDBY READY (IMSI, P-TMSI, Area, Channel Needed, QoS, DRX Parameters) (Receive Ready or Information frame)
- 23. Paging Initiated ByPCN(3G) 4. Service Request 4. Service Request 3. Paging Type1 2. Paging MS RNC MSC/VLR 3G-SGSN 1. PDP PDU or Downlink signalingPMM IDLE PMM CONNECTED (PCH paging) (IMSI, P-TMSI, Area, CN Domain Indicator, DRX parameters) › PS Paging Initiated by 3G-SGSN without RRC Connection for CS
- 24. Learning what isEPC? EPC- Evolved Packet Core Current system-3G is moving to LTE gradually. According to this new system, every network system will be in process of change. Core Network will be changed in EPC which stands for Evolved Packet Core. It’s called SAE (system architecture evolution) too. EPC consists of MME, S-GW, P-GW. Here, - MME (Mobility Management Entity) ---> for bearer control - S-GW (Serving Gateway) ---> for routing and transfer user packet - P-GW (Packet Gateway) ---> for carrying User packet
- 25. LTE/EPCarchitecture Let’s compare currentsystem with EPCs!! GGSN SGSN RNC 3G MME P-GW S-GW LTE Node b/ hspa enode b U-plane C-plane * Red Character: Interface S11 S1-C S1-U S10 HLR/HSS S6a X2 Direct Tunnel ?? means - U-plane is connected between P-GW and eNodeB directly. Merit: - Speed up the wireless part. - Simplify the Dimensioning and Decrease the delay S-GWS5 V-PLMN S8 S5
- 26. NetworkEvolution 2008/0920072000 3GPP Rel-99 3GPPRel-7 3GPP Rel-8 NodeB RNC SGSN GGSN NodeB RNC SGSN GGSN eNodeB MME P+S-GW User plane directly between RAN and GW! User plane essentially outside SGSN! User plane traffic through all nodes PDNPDNPDN LTE EPC EPS SGSN GGSN RNC SGSN GGSN NodeB RNC SGSN GGSN
- 27. EPCAttachProcedure UE eNodeB MMEHSS SGW PGW PCRF NAS: Security Mode Complete S1AP: Uplink NAS Transport NAS: Attach Accept S1AP: Initial Context Setup Request Dia: Update Location (MME ID, IMSI) Dia: Update Location Answer (APN, QoS, Charging attribution) GTPCv2: Create Session Request (MME F-TEID(S11), PGW IP address (S5-C), PDN type, IMSI, bearer QoS, EBI) GTPCv2: Create Session Request (MME F-TEID(S11), PGW IP address (S5-C), PDN type, IMSI, bearer QoS, EBI) Dia: Control Credit Request (Initial Request, APN, IMSI, QCI&ARP, APN-AMBR) Dia: Control Credit Answer (Initial Request, QCI&ARP, APN-MBR, Event- Trigger) GTPCv2: Create Session Response (Cause, PGW F- TEID(S5-C, S5-U), UE-IP address, Bearer QoS, EBI) GTPCv2: Create Session Response (cause, SGW F-TEID(S11, S1-U), UE IP address, Bearer QoS, PDN F-TEI D(S5-C, S5-U), EBI ) NAS: Attach Accept S1AP: Initial Context Setup Response NAS: Attach Complete NAS: Attach Complete S1AP: Uplink NAS Transport GTPCv2: Modify Bearer Request GTPCv2: Modify Bearer Response
- 28. 3G EPCTraffic Cases 2G/3G/EPS Interworking Iub Gn X2 S1-UP UTRAN Internet Evolved Packet Core GPRSPacketCore S3 S1-CP eUTRAN X2 S4 Iub Iur Iu LTE SGi S11 EPC Gb Abis 2G GERAN MME ServingGW (S-GW) GGSN SGSN BSC RNC RNC PDN GW (P-GW) S5/S8
- 29. Automation GGSN CDR waspiling up in the system because after successfully copying the CDRs mediation moved the CDR file from default location to GGSN /var/log/CDR_collected. To maintain safe disk usage an automated procedure was required. So a script was prepared to handle this requirement. #!/bin/sh ################################################################# # SCRIPT: remove_old_GGSN_CDR_v0.sh # # PURPOSE: Remove old CDRs from CDR path in GGSN # # Author: Mustafa Golam # ################################################################# now="$(date)" hostn="$(hostname)" echo "starting deletion of CDR backlog $now for GGSN $hostn" >>/var/log/CDR_Deleteion_Log cd /var/log/CDR_collected wd="$(pwd)" echo "Current Directory $wd" >> /var/log/CDR_Deleteion_Log #verification countlines="$(ls -ltr |wc -l)" echo "Total CDR files found $countlines" >>/var/log/CDR_Deleteion_Log #Deletion /usr/bin/find . -type f -mtime +3 -exec /bin/rm -rf {} ; echo "Old CDR File Deletion Completed and Remaining CDR Files $countlines" >>/var/log/CDR_Deleteion_Log The Script Managing CDR directory usage by GGSN cronjob
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