Packet core network basics

Introduction of PS Core Network Elements and little bit of EPC/LTE Network. This is introductory slides pack for a 10 class/slides set for detail introduction of 2G/3G and LTE PS Core Network.

1. Mustafa Golam PS Core Overview

2. Training Schedule

3. Basic GPRS Network Architecture SGSN GGSN Gi (IP) Gn Gs Gb Gp Gr (MAP) IP Network Inter PLMN Backbone Network IP MSC/VLR BTS BSC HLR MAP MS RNC RAN node B Gp Iu

4. MS BTS BSC RNC NODE-B MS SGSN GGSN SGSN GGSN MSC SCP/Camel HLR OSS Corporate LAN Gs SMS Um Abis Gb Ge Gn Gom Gr Gn Gn Gn Gn Um Iub Iu Gi Gi Gd GSM WCDMA ISP PCRF Extended Logical Network Architecture

5. Functional view on GPRS

6. Protocol Level Logical Network Architecture

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– Gateway 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: 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– Domain Name 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// SAPC H// 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. GPRS Attach When a MS is 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. Attach Procedure 1.Attach Request MS BSS New 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 Data Protocol (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)

15. PDP Context Activation

16. Mobile Address Allocation GGSN Address 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

17. PLMN Roaming HPLMN GGSN MS UPLMN GGSN SGSN GGSN SGSN GGSN VPLMN GGSN SGSN ISP DNS DNS APN available in Home PLMN only

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 State Transition

20. 3G Mobility State Transition

21. Routing Area Update Procedure MS RAI 2 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 By PCN (3G) 4. Service Request 4. Service Request 3. Paging Type1 2. Paging MS RNC MSC/VLR 3G- SGSN 1. PDP PDU or Downlink signaling PMM 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 is EPC? 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/EPC architecture Let’s compare current system with EPCs!! GGSN SGSN RNC 3G MME P-GW S-GW LTE Node b/ hspa e node 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-GW S5 V-PLMN S8 S5

26. Network Evolution 2008/09 2007 2000 3GPP Rel-99 3GPP Rel-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 PDN PDN PDN LTE EPC EPS SGSN GGSN RNC SGSN GGSN NodeB RNC SGSN GGSN

27. EPC Attach Procedure UE eNodeB MME HSS 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 EPC Traffic Cases 2G/3G/EPS Interworking Iub Gn X2 S1-UP UTRAN Internet Evolved Packet Core GPRS Packet Core S3 S1-CP eUTRAN X2 S4 Iub Iur Iu LTE SGi S11 EPC Gb Abis 2G GERAN MME Serving GW (S-GW) GGSN SGSN BSC RNC RNC PDN GW (P-GW) S5/S8

29. Automation GGSN CDR was piling 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

30. hmmn When you’re confused Q??