SAE and Evolved Packet Core

Transcription

1 SAE and Evolved Packet Core Farooq Bari Seattle Communications (COM-19) Society Chapter Nov. 13,

2 SAE/EPS Background Around 2005, 3GPP RAN groups initiated the LTE work and in parallel the SAE work was started in SA2 to address the system and core network aspects Main Objectives To ensure competitiveness of the 3GPP systems in a time frame of the next 10 years and beyond to enhance the capability of the 3GPP system to cope with the rapid growth in IP data traffic A mechanism to support seamless mobility between heterogeneous access networks Important parts of such a long-term evolution included reduced latency, higher user data rates, improved system capacity and coverage, and reduced overall cost for the operator A key aspect of SAE vision was flat IP Architecture and the new LTE/SAE system was to be packet only system Migration aspects were to be taken into account for the above, i.e. how to migrate from the existing architecture 2

3 Brief status of Work 3GPP SA2 SAE/EPS work resulted in two new stage 2 technical specifications: TS :GPRS Enhancements for E-UTRAN Access TS :Architecture enhancements for non-3gpp accesses In addition several other specifications (e.g. TS for policy Control and Charging) were updated to accommodate EPS architecture. Stage 2 completed June 2008 Target completion date for stage 3 is December

4 Evolved Packet System: EPC & EUTRAN Evolved Packet System (EPS) provides IP connectivity using the EPC and E-UTRAN. High Level Functions of EPC Network Access Control Functions Packet Routeing and Transfer Functions Mobility Management Functions Security Functions Radio Resource Management Functions Network Management Functions Covers both roaming and non-roaming scenarios and covers all aspects, including mobility between E-UTRAN and pre-e-utran 3GPP radio access technologies, policy control and charging, and authentication Local breakout of IP traffic via the visited PLMN is supported, when network policies and user subscription allow it. Local breakout may be combined with support for multiple simultaneous PDN connections 4

5 TS GPRS Enhancements for E- UTRAN Access 5

6 Non-Roaming Architecture UTRAN SGSN GERAN S3 S1-MME MME S11 LTE-Uu S10 UE E-UTRAN S1-U HSS S6a S4 Serving Gateway S12 S5 Gx PDN Gateway PCRF SGi Rx Operator's IP Services (e.g. IMS, PSS etc.) UTRAN Ref: TS SGSN GERAN S3 S5 S1-MME MME S11 LTE-Uu S10 UE E-UTRAN S1-U HSS S6a S4 Serving Gateway S12 Gx PDN Gateway PCRF SGi Rx Operator's IP Services (e.g. IMS, PSS etc.) 6

7 Key Evolved Packet Core Entities Mobility Management Entity (MME) MME is similar in function to control plane of legacy SGSN. It manages mobility aspects in 3GPP accesses such as gateway selection, tracking area list management etc. Serving Gateway (SGW) SGW terminates the interface towards E-UTRAN. It is the local mobility anchor point for inter-enodeb handovers and also provides an anchor for inter-3gpp mobility. Other responsibilities include lawful intercept, charging and some policy enforcement. Packet Data Network Gateway (PGW) PGW terminates the SGi interface towards the PDN. It is the key node for policy enforcement and charging data collection. It also provides the anchor point for mobility with non-3gpp accesses. SGW and PGW can be implemented in a single box. 7

8 GW selection process PDN GW selection function: The PDN GW selection function allocates a PDN GW that shall provide the PDN connectivity for the 3GPP access The function uses subscriber information provided by the HSS and possibly additional criteria. For each of the subscribed PDNs, the HSS provides: an IP address of a PDN GW and an APN, or an APN and an indication for this APN whether the allocation of a PDN GW from the visited PLMN is allowed or whether a PDN GW from the home PLMN shall be allocated. Serving GW selection function The Serving GW selection function selects an available Serving GW to serve a UE The selection based on network topology Other criteria for Serving GW selection include load balancing between Serving GWs 8

9 PCRF PCRF is the policy and charging control element In non-roaming scenario, there is only a single PCRF in the HPLMN associated with one UE's IP-CAN session In a roaming scenario with local breakout of traffic there may be two PCRFs associated with one UE's IP-CAN session H-PCRF that resides within the H-PLMN terminates the Rx reference point for home network services terminates the S9 reference point for roaming with local breakout V-PCRF that resides within the V-PLMN terminates the Gx and S9 reference points for roaming with local breakout terminates Rx for roaming with local breakout and visited operator's Application Function 9

10 Roaming Architecture 1 HSS PCRF Gx Rx S6a PDN Gateway SGi Operator s IP Services (e.g. IMS, PSS etc.) HPLMN VPLMN UTRAN S8 SGSN GERAN S1 - MME S3 MME S4 S12 S11 UE LTE - Uu E - UTRAN S10 S1- U Serving Gateway Roaming architecture for 3GPP accesses. Home routed traffic Ref: TS

11 Roaming Architecture 2 HSS H - PCRF Rx S6a HPLMN S9 Home Operator s IP Services VPLMN UTRAN S G SN GERAN S1 - MME S3 MME S4 S12 Gx V - PCRF S11 UE "LTE- Uu" E - UTRAN S10 S1 - U Serving G ateway S 5 PDN G ateway SGi Visited Oper ator PDN Ref: TS Roaming architecture for local breakout, with home operator's application functions only 11

12 Roaming Architecture 3 HSS H -PCRF S6a HPLMN S9 VPLMN UTRAN S GSN GERAN S1- MME S3 MME S4 S12 S7 V -PCRF Rx+ UE LTE - Uu E- UTRAN S10 S1- U S11 Serving G ateway S5 PDN Gateway SGi Home Operator s IP Services Roaming architecture for local breakout, with visited operator's application functions only Ref: TS

13 SAE QoS Concepts The EPS bearer For E-UTRAN access to the EPC the PDN connectivity service is provided by an EPS bearer in case of GTP-based S5/S8, and by an EPS bearer concatenated with IP connectivity between Serving GW and PDN GW in case of PMIP-based S5/S8 An EPS bearer is the level of granularity for bearer level QoS control in the EPC/E-UTRAN The initial bearer level QoS parameter values of the default bearer are assigned by the network, based on subscription data The decision to establish or modify a dedicated bearer can only be taken by the EPC, and the bearer level QoS parameter values are always assigned by the EPC Bearer level QoS parameters The bearer level (i.e. per bearer or per bearer aggregate) QoS parameters are QCI, ARP, GBR, MBR, and AMBR Each EPS bearer is associated with the following bearer level QoS parameters: QoS Class Identifier (QCI); Allocation and Retention Priority (ARP). Each GBR bearer is additionally associated with the following bearer level QoS parameters: Guaranteed Bit Rate (GBR); Maximum Bit Rate (MBR). Each APN is associated with an Aggregate Maximum Bit Rate (APN AMBR). Each UE is associated with UE Aggregate Maximum Bit Rate (UE AMBR). 13

14 The EPS bearer with GTP-based S5/S8 Application / Service Layer UL Service Data Flows DL Service Data Flows UL-TFT DL - TFT UL - TFT RB -ID DL-TFT S5/S8a- TEID RB -ID S1 - TEID S1-TEID S5/S8a -TEID UE enodeb enb Serving GW PDN GW Radio Bearer S1 Bearer S5/S8 Bearer Ref: TS

15 Support for multiple PDNs and local breakout Multiple PDN support: Simultaneous exchange of IP traffic to multiple PDNs is supported in the EPS, when the network policies and user subscription allow it It shall be possible to support in the EPS simultaneous exchange of IP traffic to multiple PDNs through the use of separate PDN GWs or single PDN GW The EPS also supports an UE-initiated connectivity establishment to separate PDN GWs or single PDN GW in order to allow parallel access to multiple PDNs Support of Local Breakout Local breakout of IP traffic via the visited PLMN is supported, when network policies and user subscription allow it Local breakout may be combined with support for multiple simultaneous PDN connections 15

16 Inter-working with Legacy 3GPP systems UE GERAN Gn/Gp UTRAN SGSN Gn S1-MME MME S11 S10 E-UTRAN S1u vplmn Gr S6a Gp SGW S8 hplmn HSS Gx PGW PCRF SGi Rx Operator's IP Services ( e.g. IMS, PSS etc.) Roaming and inter access mobility between Gn/Gp 2G and/or 3G SGSNs and an MME/S-GW are enabled by: - Gn functionality as specified between two Gn/Gp SGSNs, which is provided by the MME, and - Gp functionality as specified between Gn/Gp SGSN and Gn/Gp GGSN that is provided by the P-GW. All this Gp and Gn functionality bases on GTP version 1 only. Ref: TS

17 Key concepts in mapping between EPS and pre-rel-8 QoS parameters QCI 1 2 FFS There is a one-to-one mapping between an EPS bearer and a PDP context. The EPS bearer parameters ARP is mapped one-to-one to/from the pre-rel-8 bearer parameter ARP. The EPS bearer parameters GBR and MBR of a GBR EPS bearer are mapped one-toone to/from the pre-rel-8 bearer parameters GBR and MBR of a PDP context associated with Traffic class 'conversational' or 'streaming' Conversational Conversational Streaming Traffic Class Streaming Interactive Interactive Interactive Interactive Background Traffic Handling Priority N/A N/A N/A N/A N/A Signalling Indication N/A N/A N/A N/A Yes No No No N/A Source Statistics Descriptor Speech Unknown Speech Unknown N/A N/A N/A N/A N/A 17

18 TS Architecture enhancements for non-3gpp accesses 18

19 TS : Architecture enhancements for non-3gpp accesses The specification defines an architecture based on IETF based protocols for eutran (LTE) access Non-3GPP accesses such as WLAN, WIMAX, 3GPP2 The architecture using IETF based mobility procotol for eutran better suited for operators with legacy non-3gpp accesses that are transitioning over to 3GPP Besides dealing with some specific inter-working issues for 3GPP2 systems, the specification provides multiple ways for legacy 3GPP and LTE accesses to inter-work with non- 3GPP accesses which can in general be classified into client based mobility mechanisms and network based mobility mechanisms Although this allows flexibility but this also makes the inter-working much more complex 19

20 Mobility Management Selection No Mobility Mode or protocol is currently mandated for inter-working with non-3gpp accesses Static Configuration For networks deploying a single IP mobility management mechanism, the statically configured mobility mechanism can be access type and/or roaming agreement specific. The information about the mechanism to be used in such scenario is expected to be provisioned into the terminal (or the UICC) and the network Networks Supporting Multiple IP IP MM protocol selection between Network Based Mobility (NBM) and DSMIPv6 Decision on IP address preservation if NBM is selected Example uses of IPMS include initial attach to a non-3gpp access, when the IP MM protocol selection is performed to decide how to establish IP connectivity for the UE. handover without optimization from a 3GPP access to a non-3gpp access, where the IP MM protocol selection is performed to decide how to establish IP connectivity for the UE over non-3gpp access. change of access between between two non-3gpp accesses 20

21 Terminology: Trusted and un trusted non-3gpp accesses No precise definition but it can be safely assumed that Trusted non-3gpp accesses can be the one that is owned and operated by the LTE HPLMN. An example of this can be the inter-working of a LTE operator with its legacy 3GPP2 network. Untrusted non-3gpp accesses can be the one that is not owned and/or operated by the LTE HPLMN. An example of this can be a 3 rd party WLAN inter-working with an LTE HPLMN. The trust relationship of a non-3gpp access network is made known to the UE with one of the following options: 1)If the non-3gpp access supports 3GPP-based access authentication, the UE discovers the trust relationship during the 3GPP-based access authentication. 2)The UE operates on the basis of pre-configured policy in the UE. 21

22 Non-Roaming Architecture for 3GPP Accesses within EPS using PMIP-based S5 HSS 2G/3G SGSN S1-MME E-UTRAN 3GPP Access S3 MME S10 S1-U S4 S11 S6a Serving Gateway S5 PMIP Gxc S7c PDN Gateway Gx S7 PCRF SGi Rx+ Operator's IP Services (e.g. IMS, PSS etc.) Ref: TS

23 Roaming Architecture for 3GPP Accesses within EPS using PMIPbased S8 HSS HPLMN S6a Gx PDN Gateway hpcrf Rx SGi Operator's IP Services (e.g. IMS, PSS etc.) 2G/3G SGSN S1-MME E-UTRAN 3GPP Access S4 S3 MME S10 S11 Serving Gateway S8 Gxc vpcrf S9 S1-U VPLMN Ref: TS

24 Non-Roaming Architecture using S5, S2a, S2b HSS SW x S6a PC RF G xc G x R x HPLM N 3G PP Access Serving G ateway S5 S2a PDN Gateway S2b epdg G xb SW n SGi S6b SW m Operator's IP Services (e.g. IM S, PSS etc.) 3GPP AAA Server N on-3gpp N etworks Trusted N on-3gpp IP Access G xa SW u Untrusted Non-3GPP IP Access UE SW a STa Ref: TS

25 Non-Roaming Architecture using S5, S2c HSS SWx S6a Gxc PCRF Rx 3GPP Access Serving Gateway S5 Gx PDN Gateway SGi Operator's IP Services (e.g. IMS, PSS, etc.) HPLMN epdg Gxb SWn S6b SWm 3GPP AAA Server Non-3GPP Networks Trusted Non- 3GPP IP Access Gxa Untrusted Non- 3GPP IP Access SWa STa S2c Ref: TS S2c UE S2c 25

26 Routed Six possible roaming scenarios in specifications H P L M N S 6 a H S S G x P D N G a te w a y h P C R F R x S G i S 6 b S W x O p e ra to r's IP S e rv ic e s (e.g. IM S, P S S e tc.) 3 G P P A A A S e rv e r S 8 S 2 b v P C R F S 9 S W d 3 G P P A c c e s s V P L M N S e rv in g G a te w a y G x c S 2 a G x b e P D G S W m 3 G P P A A A P ro x y N o n -3 G P P N e tw o rk s G x a S W n T ru s te d N o n -3 G P P IP A c c e s s U n tru s te d N o n -3 G P P IP A c c e s s S W a S T a Ref: TS

27 Additional functionalities or variations in architectural entities - Serving GW 1. local non-3gpp anchor for the case of roaming when the non-3gpp IP accesses connected to the VPLMN. 2. Event reporting (change of RAT, etc.) 3. Uplink bearer binding and verification with packet dropping. 4. Mobile Access Gateway (MAG) DHCPv4 and DHCPv6 functions 5. Handling of Router Solicitation and Router Advertisement messages if PMIP based S5 and S8 is used 1. PDN GW 1. user plane anchor for mobility between 3GPP access and non-3gpp access. 2. LMA if PMIP-based S5 or S8 is used. 3. DSMIPv6 Home Agent if S2c is used. 27

28 Additional functionalities or variations in architectural entities because of PMIP MME 1. Support for HRPD PCRF Home PCRF 1. Terminates the Gx reference point for roaming with home routed traffic; 2. Terminates the Gxa, Gxb or Gxc/S9 reference points as appropriate for the IP-CAN type. Visited PCRF 1. Terminates the Gxa, Gxb or Gxc reference points as appropriate for the IP-CAN type; 2. Terminates the S9 reference point. 28

29 Evolved Packet Data Gateway (epdg) 1. Functionality defined for the PDG in TS for the allocation of a remote IP address: An IP address local to the epdg which can be used as CoA for S2c; An IP address specific to a PDN when S2b is used; 2. Routing of packets from/to PDN GW (and from/to Serving GW if it is used as local anchor in VPLMN) to/from UE; 3. De-capsulation/Encapsulation of packets for IPSec and PMIP tunnels (the latter only if network based mobility (S2b) is used); 4. Mobile Access Gateway (MAG) if network based mobility (S2b) is used; 5. Tunnel authentication and authorization (termination of IKEv2 signaling and relay via AAA messages); 6. Local mobility anchor within untrusted non-3gpp access networks using MOBIKE (if needed); 7. Transport level packet marking in the uplink; Enforcement of QoS policies based on information received via AAA infrastructure; Lawful Interception. 29

30 PMIP (S5/S8) QoS and Policy Aspects Application / Service Layer Service Data Flows Service Data Flows DL-PF S1-TE-ID DL-PF TNL QoS UL Packet Filter RB-ID S1-TE-ID DL Packet Filter UL-PF RB-ID DL Packet Filter UE enb Serving GW PDN GW S1-TE-ID TNL QoS Radio Bearer S1 Bearer IP Transport Leg 30

31 PMIP-GTP roaming using direct peering P M IP V P L M N v P C R F S 9 G T P H P L M N P C R F G x c S e rv in g G W (P M IP ) P M IP T o w a rd s o th e r P M IP o p e ra to rs G T P G x P D N G W (G T P ) S e rv in g G W (G T P ) a ) P M IP V P L M N G T P H P L M N G T P V P L M N S 9 P M IP H P L M N h P C R F S e rv in g G W (G T P ) G T P T o w a r d s o th e r P M IP o p e ra to rs P M IP G x P D N G W (P M IP ) G x P D N G W (G T P ) Ref: TS b ) G T P V P L M N P M IP H P L M N 31

32 PMIP-GTP roaming using direct peering with local breakout GTP VPLMN PMIP HPLMN vpcrf S9 hpcrf Serving GW (GTP) Gx PMIP VPLMN GTP HPLMN Serving GW (GTP) GTP PDN GW (GTP) vpcrf S9 hpcrf Serving GW (PMIP) Gxc Gx Serving GW (PMIP, GTP) PMIP PDN GW (PMIP) Ref: TS

33 PMIP-GTP roaming using interworking proxy PMIP - VPLMN Interworking Proxy GTP - HPLMN PCRF S9 PCRF Gxc Protocol converter Gx Serving GW S8 PMIP S8 GTP PDN GW a) GTP HPLMN - PMIP VPLMN GTP - VPLMN Interworking Proxy PMIP - HPLMN S9 PCRF Protocol converter Gx Serving GW S8 GTP S8 PMIP PDN GW Ref: TS b) PMIP HPLMN - GTP VPLMN 33

34 Network discovery and selection UE 3GPP IP Access or Trusted/Untrusted Non-3GPP IP Access S14 ANDSF 34

35 Non-3GPP Identities NAI RFC 4282 based user identification defined in TS shall be used. The username part of NAI shall be based on IMSI. This applies to S2a, S2b and S2c reference points. User identification in non-3gpp accesses may require additional identities that are out of the scope of 3GPP. These user identities, if not compliant to TS are however not sufficient to identify a user in the 3GPP Evolved Packet Core. 35

36 WiMAX inter-working In Release, 8 WiMAX support is based on the following principles The EPS shall support mechanisms for delivery of inter-system mobility, network discovery and selection policies over the Sx interface. The policies shall contain information e.g. on availability of WiMax access networks that control the UE selection of available WiMax access network and the UE decision and triggering of 3GPP - WiMax handovers The handover procedure will be executed according to the S2a/S2c procedures. 36

37 CDMA inter-working HRPD AN IOS PDSN S101 Sx- U S2a Operator's IP services Rx + S1- MME MME PCRF S11 S7 UE E- UTRAN S10 S1- Serving GW S5 PDN GW SGi Ref: TS

38 3GPP Releases and SAE Features Current plan is to Meet the completion deadline of December 2008 by including only the SAE essentials and a shortened list of non-essentials in Release 8 Aim for a Short Release 9 (~1 year after release 8) to address remaining SAE features that could not be included in release 8 Aim for a Short Release 10 (~1 year after Release 9) for handling IMT/LTE Advanced features List of Release 8 SAE Features High level and common (for all accesses) functions (e.g. Roaming, QoS, etc ) SAE for LTE - GTP variant SAE LTE - PMIP variant Interoperation between LTE and 2G/3G LTE and CDMA2000 Single Radio Voice Call Continuity (SRVCC) Circuit Switched Fall Back (CSFB) List of expected Release 9 SAE Features SAE aspects of Emergency Calls Functions and procedures for SAE to support LTE MBMS Functions and procedures for SAE to support Control Plane LCS CS over EPS Single Radio Aspects of SAE for Optimised Handover with WiMAX Home Node B. 38

39 Backup 39

40 Reference Points Ref: TS S1-MME: Reference point for the control plane protocol between E-UTRAN and MME. S1-U: Reference point between E-UTRAN and Serving GW for the per bearer user plane tunnelling and inter enodeb path switching during handover. S3: It enables user and bearer information exchange for inter 3GPP access network mobility in idle and/or active state. S4:It provides related control and mobility support between GPRS Core and the 3GPP Anchor function of Serving GW. In addition, if Direct Tunnel is not established, it provides the user plane tunnelling. S5: It provides user plane tunneling and tunnel management between Serving GW and PDN GW. It is used for Serving GW relocation due to UE mobility and if the Serving GW needs to connect to a non-collocated PDN GW for the required PDN connectivity. S6a: It enables transfer of subscription and authentication data for authenticating/authorizing user access to the evolved system (AAA interface) between MME and HSS. Gx: It provides transfer of (QoS) policy and charging rules from PCRF to Policy and Charging Enforcement Function (PCEF) in the PDN GW. S8: Inter-PLMN reference point providing user and control plane between the Serving GW in the VPLMN and the PDN GW in the HPLMN. S8 is the inter PLMN variant of S5. S9: It provides transfer of (QoS) policy and charging control information between the Home PCRF and the Visited PCRF in order to support local breakout function. S10: Reference point between MMEs for MME relocation and MME to MME information transfer. S11: Reference point between MME and Serving GW. S12: Reference point between UTRAN and Serving GW for user plane tunneling when Direct Tunnel is established. It is based on the Iu-u/Gn-u reference point using the GTP-U protocol as defined between SGSN and UTRAN or respectively between SGSN and GGSN. Usage of S12 is an operator configuration option. S13: It enables UE identity check procedure between MME and EIR. SGi: It is the reference point between the PDN GW and the packet data network. Packet data network may be an operator external public or private packet data network or an intra operator packet data network, e.g. for provision of IMS services. This reference point corresponds to Gi for 3GPP accesses. 40 Rx The Rx reference point resides between the AF and the PCRF in the TS

41 Protocol assumptions The S1-U is based on GTP-U protocol The S3 is based on GTP protocol The S4 is based on GTP protocol The S5 is based on GTP protocol. PMIP variant of S5 is described in TS The S8 is based on GTP protocol. PMIP variant of S8 is described in TS Ref: TS

42 Key interfaces for inter-working with non 3GPP accesses S2a It provides the user plane with related control and mobility support between trusted non 3GPP IP access and the Gateway. S2b It provides the user plane with related control and mobility support between epdg and the Gateway. S2c It provides the user plane with related control and mobility support between UE and the Gateway. Gxa It provides transfer of (QoS) policy information from PCRF to the Trusted Non-3GPP accesses. Gxb This interface is not specified within this release of the specification. Gxc It provides transfer of (QoS) policy information from PCRF to the Serving Gateway Note: names of some of the interfaces are currently being changed in the specification 42

43 Protocols for inter-working with non 3GPP accesses S2a is based on Proxy Mobile IP. To enable access via Trusted Non 3GPP IP accesses that do not support PMIP, S2a also supports Client Mobile IPv4 FA mode S2b is based on Proxy Mobile IP S2c is based on DSMIPv6 Gx/a/b/c interfaces will be using DIAMETER Current status of critical IETF dependencies Proxy Mobile IP draft (draft-ietf-netlmmproxymip6-16.txt) is in RFC Ed. Queue DSMIVP6 draft (draft-ietf-mext-nemov4traversal-05.txt) is in IETF WG last call (?) 43