1

SAE and Evolved Packet

Core

Farooq Bari

Seattle Communications (COM-19) Society Chapter

Nov. 13, 2008

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

3

Brief status of Work

� 3GPP SA2 SAE/EPS work resulted in two new stage 2 technical specifications:

� TS 23.401:GPRS Enhancements for E-UTRAN Access

� TS 23.402:Architecture enhancements for non-3GPP accesses

� In addition several other specifications (e.g. TS 23.203 for policy Control and Charging) were updated to accommodate EPS architecture.

� Stage 2 completed June 2008

� Target completion date for stage 3 is December 2008

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, andauthentication

� 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

5

TS 23.401

GPRS Enhancements for E-UTRAN Access

6

Non-Roaming Architecture

Ref: TS 23.401

SGi

S12

S3

S1-MME

PCRF

Gx

S6a

HSS

Operator's IP Services

(e.g. IMS, PSS etc.)

Rx

S10

UE

SGSN

LTE-Uu

E-UTRAN

MME

S11

S5 Serving Gateway

PDN Gateway

S1-U

S4

UTRAN

GERAN

SGi

S12

S3

S1-MME

PCRF

Gx

S6a

HSS

Operator's IP Services

(e.g. IMS, PSS etc.)

Rx

S10

UE

SGSN

LTE-Uu

E-UTRAN

MME

S11

S5

ServingGateway

PDN Gateway

S1-U

S4

UTRAN

GERAN

7

Key Evolved Packet Core EntitiesMobility 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.

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

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

10

Roaming Architecture 1

Roaming architecture for 3GPP accesses. Home routed traffic

Ref: TS 23.401

S6a

HSS

S8

S3

S1 - MME

S10

UTRAN

GERAN

SGSN

MME

S11

Serving

Gateway UE

“ LTE

- Uu

” E - UTRAN

S12

HPLMN

VPLMN

PCRF

Gx Rx

SGi

Operator’s IP Services

(e.g. IMS, PSS etc.)

PDN

Gateway

S1- U

S4

11

Roaming Architecture 2

Roaming architecture for local breakout, with home operator's application functions only

Ref: TS 23.401

S6a

HSS

S 5

S3

S1 - MME

S10

GERAN

UTRAN

S G SN

MME

S11

Serving G ateway UE

"LTE- Uu"

E - UTRAN

S4

HPLMN

VPLMN

V - PCRF

Gx

SGi

PDN G ateway

S1 - U

H - PCRF

S9

Home Operator’s IP

Services

Rx

Visited Oper ator PDN

S12

12

Roaming Architecture 3

S6a

HSS

S5

S3

S1- MME

S10

UTRAN

S GSN

MME

S11

Serving G ateway UE

“ LTE

- Uu ”

E- UTRAN

S4

HPLMN

VPLMN

V -PCRF

S7

SGi

PDN Gateway

S1- U

H -PCRF

S9

Home Operator’s IP

Services

Rx+

GERAN

S12

Roaming architecture for local breakout, with visited operator's application functions only

Ref: TS 23.401

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 QoSparameters:

� 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).

14

The EPS bearer with GTP-based

S5/S8

Serving GW PDN GWeNB

Radio Bearer S5/S8 Bearer

Application / Service Layer

UL - TFT → RB -ID

DL Service Data Flows

DL - TFT

DL-TFT → S5/S8a- TEID

RB -ID ↔ S1 - TEID

S1 Bearer

S1-TEID ↔ S5/S8a -TEID

UE

UL Service Data Flows

UL-TFT

Serving GW PDN GWeNodeB

- →

-

- → -

- ↔ - - ↔ -

UE

-

Ref: TS 23.401

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

16

Inter-working with Legacy 3GPP

systems

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.

SGi

Gp

Gn S1-MME

PCRF

Gx

S6a

HSS

S10

UE

GERAN

UTRAN

Gn/Gp

SGSN

E-UTRAN

MME

S11

S8

SGW PGW

Rx

Gr vPLMN hPLMN

S1u

Operator's IP Services ( e.g. IMS, PSS etc.)

Ref: TS 23.401

17

Key concepts in mapping between

EPS and pre-Rel-8 QoS parameters

N/AN/AN/ABackground9

N/ANo3Interactive8

N/ANo2Interactive6

N/ANo1Interactive7

N/AYes1Interactive5

UnknownN/AN/AStreaming3

SpeechN/AN/AStreamingFFS

UnknownN/AN/AConversational2

SpeechN/AN/AConversational1

Source

StatisticsDescriptor

Signalling

Indication

TrafficHandlingPriority

TrafficClass

QCI

•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-to-one to/from the pre-Rel-8 bearer parameters GBR and MBR of a PDP context associated with Traffic class 'conversational' or 'streaming'

18

TS 23.402

Architecture enhancements for non-3GPP accesses

19

TS 23.402 : 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

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

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 3rd 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.

22

Non-Roaming Architecture for

3GPP Accesses within EPS using

PMIP-based S5

Ref: TS 23.402

SGi

PCRF

S7

S6a

HSS

Operator's IP Services

(e.g. IMS, PSS etc.)

S1-U

S1-MME

E-UTRAN

2G/3G SGSN S4

S3

S5 PMIP

Rx+

PDN Gateway

MME S11

S10

S7c

Serving Gateway

3GPP Access

Gxc

Gx

23

Roaming Architecture for 3GPP

Accesses within EPS using PMIP-

based S8

Ref: TS 23.402

hPCRF S6a

HSS

PDN Gateway HPLMN

VPLMN

S8

vPCRF

S1-U

S1-MME

E-UTRAN

2G/3G SGSN S4

S3 MME

S11

S10

Gxc

S9

SGi

Gx

Operator's IP Services

(e.g. IMS, PSS etc.)

Rx

3GPP Access

Serving Gateway

24

Non-Roaming Architecture using S5,

S2a, S2b

Ref: TS 23.402

SGi

PC RF

G x

HSS

S2b

SW n

Operator's IP Services

(e.g. IM S, PSS etc.)

SW m

SW x

Untrusted Non-3GPP IP

Access SW a

HPLM N

N on-3GPP N etworks

S6b

R x

PDN Gateway

ePDG 3GPP AAA Server

G xb

S2a

G xa

Trusted N on-3GPP IP

Access STa

G xc

S5

S6a

3G PP Access

Serving G ateway

UE

SW u

25

Non-Roaming Architecture using S5,

S2c

SGi

PCRF

Gx

HSS

SWn

Operator's IP Services (e.g. IMS, PSS, etc.)

SWm

SWx

Untrusted Non- 3GPP IP

Access SWa

HPLMN

Non-3GPP Networks

S6b

Rx

PDN Gateway

Trusted Non-3GPP IP Access

STa

S2c S2c

ePDG 3GPP AAA

Server

UE

Gxa

Gxb

Gxc

S5

S6a

S2c

3GPP Access

Serving Gateway

Ref: TS 23.402

26

Routed

Six possible roaming scenarios in

specifications

Ref: TS 23.402

h P C R F

H S S

T ru s te d N o n -3 G P P IP

A c c e s s

P D N G a te w a y

H P L M N

S W d

N o n -3 G P P N e tw o rk s

V P L M N

v P C R F

3 G P P A A A P ro x y

S T a

3 G P P A A A S e rv e r

S 2 a

G x a

S 9

S G i

G x

S 6 b

O p e ra to r 's IP S e rv ic e s

( e .g . IM S , P S S e tc . )

R x S W x

S W n

e P D G

S W a

U n tru s te d N o n -3 G P P IP

A c c e s s

S W m

S 2 b

G x b G x c

S 8

S 6 a

3 G P P A c c e s s

S e rv in g G a te w a y

27

Additional functionalities or variations

in architectural entities

- Serving GW1. 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 GW1. 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.

28

Additional functionalities or

variations in architectural entities

because of PMIP

MME1. Support for HRPD

PCRFHome 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.

29

Evolved Packet Data Gateway

(ePDG)1. Functionality defined for the PDG in TS 23.234 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.

30

PMIP (S5/S8) QoS and Policy

Aspects

eNB PDN GW UE

Service Data Flows

UL Packet Filter

UL-PF→RB-ID

Service Data Flows

DL Packet Filter

DL-PF→S1-TE-ID

RB-ID↔S1-TE-ID

Radio Bearer S1 Bearer

Application / Service Layer

IP Transport Leg

Serving GW

DL Packet Filter

DL-PF→TNL QoS

S1-TE-ID→TNL QoS

31

PMIP-GTP roaming using direct

peering

S e rv in g G W

(P M IP )

v P C R F

G x c

G T P – H P L M N P M IP – V P L M N

P M IP G T P

S 9

S e rv in g G W

(G T P )

T o w a rd s o th e r P M IP

o p e ra to rs

P D N G W (G T P )

P C R F

G x

G T P

T o w a r d s o th e r P M IP

o p e ra to rs

G T P – V P L M N

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

b ) G T P V P L M N – P M IP H P L M N

P D N G W (P M IP )

h P C R F

G x

P M IP – H P L M N

P M IP

S 9

P D N G W (G T P )

G x

Ref: TS 23.402

32

PMIP-GTP roaming using direct

peering with local breakout

Serving GW

(PMIP)

Serving GW

(PMIP, GTP)

PDN GW

(PMIP)

vPCRF

PMIP

hPCRF

Gx

S9

PMIP – VPLMN GTP – HPLMN

Gxc

Serving GW

(GTP)

Serving GW

(GTP)

PDN GW

(GTP)

vPCRF

GTP

hPCRF

Gx

S9

GTP – VPLMN PMIP – HPLMN

Ref: TS 23.402

33

PMIP-GTP roaming using inter-

working proxy

Serving GW

PCRF

Gxc

GTP - HPLMN PMIP - VPLMN

S8 PMIP S8 GTP

S9

Interworking Proxy

PDN GW

PCRF

Gx Protocol converter

a) GTP HPLMN - PMIP VPLMN

Protocol converter

GTP - VPLMN Interworking Proxy PMIP - HPLMN

b) PMIP HPLMN - GTP VPLMN

Serving GW

S8 GTP S8 PMIP

S9

PDN GW

PCRF

Gx

Ref: TS 23.402

34

Network discovery and selection

UE ANDSF

S14 3GPP IP Access or Trusted/Untrusted

Non-3GPP IP Access

35

Non-3GPP Identities

� NAI RFC 4282 based user identification defined in TS 23.003 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 23.003 are however not sufficient to identify a user in the 3GPP Evolved Packet Core.

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 - WiMaxhandovers

� The handover procedure will be executed according to the S2a/S2c procedures.

37

CDMA inter-working

PDN

GW

S1-

MME

S10

MME

S11

UE E-

UTRAN

S7

SGi S1-

PCRF

Operator's IP

services

Rx

+

S2a

S101

HRPD

AN PDSN IOS

Serving

GW

S5

Sx-

U

Ref: TS 23.402

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/3GLTE 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� ……….

39

Backup

40

Reference Points� 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 Gifor 3GPP accesses.

� Rx The Rx reference point resides between the AF and the PCRF in the TS 23.203.

Ref: TS 23.401

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 23.402

� The S8 is based on GTP protocol. PMIP variant of S8 is described in TS 23.402

Ref: TS 23.401

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

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-netlmm-proxymip6-16.txt) is in RFC Ed. Queue

� DSMIVP6 draft (draft-ietf-mext-nemo-v4traversal-05.txt) is in IETF WG last call (?)