Mobile IPv6 deployment opportunities in next generation 3GPP networks

I. GuardiniE. DemariaM. La Monaca

2

Overview of SAE/LTE

• TerminologySAE (System Architecture Evolution): core network/system aspectsLTE (Long Term Evolution): new radio access (E-UTRAN)

• Main system characteristicssupport for packet services onlyOFDM radio technologypeak throughput per user : 100 Mbps DL and 50 Mbps UL (with a 20MHz channel width)multi-access core network: GERAN, UTRAN, E-UTRAN and non-3GPP

• Specifications to be completed by 2008

3

Logical architecture: non roaming

S5 SGi

S4

S3

S1 (CP)

PCRF

S7

S6a

HSS

Rx+

S10

2G/3GSGSN

S11

ServingGateway

S5

Operator IP services(e.g. IMS, PSS, ..)

MME

E-UTRANPDN

Gateway

ePDG

Untrusted non 3GPP IP access

Trusted non 3GPP IP access

HSS

S2a

S2b

S1 (UP)

eNB

eNB

X2

eNB: evolved Node B

MME: Mobility Management Entity (similar to the control part of the SGSN)

PDN GW: access gateway towards Packet Data Networks (similar to the GGSN)

SGi: interface towards Internet/Intranet (equivalent to Gi interface in GPRS)

UTRAN

GERAN

LegacyNetworks

4

Interworking with non 3GPP accesses (I)

• SAE supports both host-based and network-based mobility management solutions

Dual-Stack MIPv6 (host-based)Proxy MIPv6 and MIPv4 in Foreign Agent mode (network-based)

• PDN GW works as MIP/PMIP Home Agentwhen connected to a 3GPP access the UE can be assumed to be at home in MIP sense

mobility within 3GPP accesses (E-UTRAN, UTRAN and GERAN) is managed in a network-based fashion using 3GPP-specific protocols

service continuity is guaranteed in case the UE moves from a 3GPP access to a non 3GPP access (or vice versa)

the UE communicates using the same IP address independently of the access network it is attached to

5

Interworking with non 3GPP accesses (II)

• SAE distinguishes between “trusted” and “untrusted” non 3GPP accesses

• It is up to the operator to decide if a non 3GPP access is trusted or untrusted

the decision is not based just on the access network technology but may depend also on business considerations

• Interworking with an untrusted access is performed via an evolved PDG (ePDG)

the ePDG is similar to a VPN concentratorthe UE has to establish an IPsec tunnel with the ePDG to access operator’s servicesthe ePDG may implement IP mobility protocols (e.g. PMIPv6)

6

Interworking with non 3GPP accesses (III)

• Interworking with a trusted access is performed using a more lightweight procedure

the UE does not need to establish an IPsec tunnel with the ePDG in advanceMIP or PMIP protocols can be used directly between the non 3GPP access network and the SAE core network

the non 3GPP access gateway (e.g. ASN GW in case of mobile WiMAX) can run PMIPv6

7

Interworking with non 3GPP accesses (IV)

SGi

S7

HSS

Rx+S4

S3

S1 (CP)

S10

2G/3GSGSN

S11

MME

S1 (UP)

E-UTRAN

S6a

ServingGateway

Operator IP services(e.g. IMS, PSS, ..)

S2a

S2b

UE

S2c3GPP AAA

Server

Wa*

Ta*

Wm*

S6c

Wx*PCRF

PDNGateway

ePDG

Untrusted non 3GPP IP access(network-based)

Trusted non 3GPP IP access(network-based)

HSS

HAHA

Trusted/untrusted non 3GPP

(host-based)

8

Protocols on non 3GPP interfaces

• The protocols that have been selected for mobility between 3GPP and non 3GPP accesses are

S2a reference point (trusted non 3GPP accesses): Proxy Mobile IPv6 and Mobile IPv4 in Foreign Agent mode

Mobile IPv4 in FA mode was requested by CDMA2000 operators (e.g. Verizon), that want to re-use their already deployed Mobile IPv4 infrastructure

S2b reference point (untrusted non 3GPP accesses): Proxy Mobile IPv6 with dual-stack extensionsS2c reference point (host-based mobility on trusted/untrusted accesses): Dual-Stack Mobile IPv6 (DSMIPv6)

the usage of Mobile IPv4 in co-located mode is still under consideration

9

Interworking scenarios: non roaming

ServingGW

PDNGW

3GPPaccess

Trustednon 3GPP

Untrustednon 3GPP

ePDG

UE

S2a S2b

SGiS5

S1u, S4,S11

Proxy Mobile IPv6or MIPv4 in FA mode

ServingGW

3GPPaccess

Trustednon 3GPP

Untrustednon 3GPP

ePDG

UE

S2c S2c

SGiS5

S1u, S4,S11

PDNGW

Dual-StackMobile IPv6

Network-basedMobility

Host-basedMobility

10

Interworking scenarios: roaming (I)

ServingGW

PDNGW

3GPPaccess

ServingGW

Trustednon 3GPP

Untrustednon 3GPP

ePDG

3GPPaccess

HPLMN

VPLMN

UE

S2aS2b

S1u, S4,S11

S8b

SGiS5

S1u, S4,S11

ProxyMobile IPv6

ServingGW

PDNGW

3GPPaccess

ServingGW

Trustednon 3GPP

Untrustednon 3GPP

ePDG

3GPPaccess

HPLMN

VPLMN

UE

S2a S2b

S1u, S4,S11

S8a/b

SGiS5

S1u, S4,S11

GTP or ProxyMobile IPv6

PMIPv6 orMIPv4 in FA mode

Network-basedMobility

Proxy Mobile IPv6

11

Interworking scenarios: roaming (II)

ServingGW

3GPPaccess

ServingGW

Trustednon 3GPP

Untrustednon 3GPP

ePDG

3GPPaccess

HPLMN

VPLMN

UE

S2c S2c

S1u, S4,S11

S8a/b

SGiS5

S1u, S4,S11

PDNGW

Dual-StackMobile IPv6

GTP or ProxyMobile IPv6

Host-basedMobility

12

Interworking scenarios: roaming (III)

• This scenario has not been officially accepted yet

the Serving GW works as a local mobility anchor and runs PMIPv6 with the PDN GW

the home address is provided by the PDN GW (i.e. the real HA)data traffic is anchored on the PDN GW the Serving GW handles local mobility through DSMIPv6the visited operator can use the Serving GW to enforce policies (e.g. charging)

not clear how to handle Serving GW relocation when the UE moves across VPLMNs

ServingGW

PDNGW

3GPPaccess

Trustednon 3GPP

Untrustednon 3GPP

ePDG

3GPPaccess

HPLMN

VPLMN

UE

S1u, S4,S11

S8b

SGiS5

S1u, S4,S11

ProxyMobile IPv6

ServingGW

S2cS2c

Host-basedMobility

13

PMIPv6/MIPv6: summary of usage scenarios

PDNGW

ServingGW

AccessGW PMIPv6PMIPv6

SGi

PDNGW

ServingGW PMIPv6DSMIPv6

SGi

PDNGW

AccessGW PMIPv6

SGi

PDNGWDSMIPv6

SGi

Roaming andnon roaming

Roaming

(S2a/b)

(S2c)

(S8b)

(S8b)

(S2a/b)

(S2c)

Cascade of PMIPv6 tunnels

Cascade of DSMIPv6 and PMIPv6 tunnels

Non 3GPPAccesses

14

Roaming with or without local anchor• Option A: no local anchor

HPLMN has to interface via PMIPv6 with all non 3GPP AGWsin VPLMNcomplicates the establishment and maintenance of roaming agreements

• Option B: local anchorPDN GW in HPLMN needs to interface via PMIPv6 just with the anchor point in VPLMNsimplifies the establishment of roaming agreementsthe visited operator can exploit the local anchor to enforce policies on UE’s data traffic

PDNGW

Non 3GPPAGWs

BSs

HPLMN VPLMN

PMIPv6 (S2a)

PDNGW

Non 3GPPAGWs

BSs

HPLMN VPLMN

ServingGW

PMIPv6 (S8b)

PMIPv6 (S2a)

No local anchorA

Local anchorB

15

Attach over S2a: trusted non 3GPP access (I)

16

Attach over S2a: trusted non 3GPP access (II)

• Step by step description of the procedure1. The initial Non-3GPP access specific L2 procedures are performed2. The EAP authentication procedure for network access is performed

involving the UE, trusted non-3GPP IP Access and the 3GPP AAA Server. In the roaming case, there may be several AAA proxies involved. The PDN GW information is returned as part of the reply from the 3GPP AAA Server to the MAG in the trusted non-3GPP access

3. After successful authentication and authorization, the L3 attachprocedure is triggered

4. MAG function of Trusted Non-3GPP IP Access sends Proxy Binding Update message to PDN GW

5. The selected PDN GW informs the 3GPP AAA Server of its address

17

Attach over S2a: trusted non 3GPP access (III)

• Step by step description of the procedure (cont’ed)6. The PDN GW processes the proxy binding update and creates a

binding cache entry for the UE. The PDN GW allocates IP address for the UE. The PDN GW then sends a proxy binding acknowledgement to the MAG function in Trusted Non-3GPP IP Access, including the IP address(es) allocated for the UE

7. The PMIPv6 tunnel is set up between the Trusted Non-3GPP IP Access and the PDN GW

8. L3 attach procedure is completed. IP connectivity between the UEand the PDN GW is set for uplink and downlink directions

18

Attach over S2b: untrusted non 3GPP access

UE ePDG PDN GW

1

2

4

5

6

7

IKEv2 (IP Address Configuration)

IPsec Tunnel

HSS/AAA

Proxy BU (MN-ID, IP addr Req)

Proxy Binding Ack(IP addr)

PMIP Tunnel

IKEv2 authentication and tunnel setup Authentication and Authorization

IPsec tunnel setup completion

3 Update PDN GW Address

19

Attach over S2b/S8b: cascade of tunnels (I)UE ePDG Serving GW

1

2

3

5

6

7

HSS/AAA

Proxy BU (MN-ID, IP Addr Request )

Proxy Binding Ack(IP Addr

Proxy BU ( MN-ID,IP Addr Req)

Proxy Binding AckIP Addr)

3GPP AAA Proxy

IKE_AUTH Authentication Authentication and Authorization Authentication and Authorization

IPsec tunnel setup completion

IKEv2 (IP Address Configuration)8

9

PDN GW

PMIP Tunnel PMIP TunnelIPsec Tunnel

4 Update PDN GWAddress

20

Attach over S2b/S8b: cascade of tunnels (II)

• Step by step description of the procedure1. The IKEv2 tunnel establishment procedure is started by the UE. The

ePDG IP address to which the UE needs to form IPsec tunnel is discovered via DNS query. The PDN GW information is returned as part of the reply from the 3GPP AAA Proxy to the ePDG. This may entail an additional name resolution step, issuing a request to a DNS Server

2. The ePDG sends the PBU message to the Serving GW3. The visited Serving GW processes the proxy binding update and

creates a binding cache entry for the UE. Then the visited Serving GW sends the PBU message to the PDN GW using its own address as the MAG address. Note that the binding cache entry on the Serving GW does not yet have the UE’s IP address information. This information will be added to the binding cache entry after step 4

21

Attach over S2b/S8b: cascade of tunnels (III)

• Step by step description of the procedure (cont’ed)4. The selected PDN GW informs the 3GPP AAA Server of its address5. The PDN GW processes the proxy binding update and creates a

binding cache entry for the UE. The PDN GW allocates an IP address for the UE. The PDN GW then sends a proxy binding ack to the Serving GW, including the IP address allocated for the UE. Once the Serving GW processes the proxy Binding Ack, it stores the UE’s IP address information in the binding cache entry

6. After the Proxy BU/Proxy BAck is successful, there is a PMIPv6 tunnel setup between the Serving GW and the PDN GW

7. The ePDG continues with the IKE_AUTH exchange

22

Attach over S2b/S8b: cascade of tunnels (IV)

• Step by step description of the procedure (cont’ed)8. The ePDG sends the final IKEv2 message with the IP address in

IKEv2 Configuration payloads. The IP address sent in the IKEv2 configuration payload is the same address that the ePDG received in the Proxy Binding Ack message

9. IP connectivity from the UE to the PDN GW is now setupany packet in the uplink direction is tunneled to the ePDG by the UE using the IPSec tunnel. The ePDG then tunnels the packet to the visited Serving GW. The visited Serving GW then tunnels the packet to the PDN GW. From the PDN GW normal IP based routing takes placeIn the downlink direction, the packet for UE (HoA) arrives at the PDN GW. The PDN GW tunnels the packet based on the binding cache entry to the visited Serving GW. The visited Serving GW tunnels the packet based on the binding cache entry to the ePDG. The ePDG then tunnels the packet to the UE via proper IPsec tunnel

23

PMIPv6: an example scenario (I)

ServingGateway

Operator IP services(e.g. IMS, PSS, ..)PDN

Gateway

ePDG

Untrusted non 3GPP IP access

S2a

S2b

UE E-UTRAN

AGW

MAGMAG

Trusted non 3GPP access

MAGMAG

Data packets HAHA

PBU

PBA

24

PMIPv6: an example scenario (II)

ServingGateway

Operator IP services(e.g. IMS, PSS, ..)PDN

Gateway

ePDG

Untrusted non 3GPP IP access

S2a

S2b

E-UTRAN

MAGMAG

Trusted non 3GPP access

MAGMAG

Data packets

UE

HAHA

AGW

PMIP tunnel

Data packets

25

PMIPv6 in 3GPP vs. PMIPv6 in IETF

• The PMIPv6 usage scenarios foreseen for 3GPP SAE/LTE present some differences with respect to those in the scope of the IETF MIP6 WG

PMIPv6 is used for inter-system handovers (i.e. handovers between 3GPP and non 3GPP accesses)

PMIPv6 is used as a global mobility protocol

PMIPv6 may be used in roaming scenarios, which means that the HAand the Proxy Mobility Agent may be located in different administrative domainsin the roaming case there is the possibility to have a cascade of PMIPv6 tunnels (AGW – Serving GW, Serving GW – PDN GW)

in this way there is a local anchor point in the visited domain, that can be used by the visited operator to enforce policies on UE’s trafficthe local anchor also simplifies the establishment of roaming agreements

26

Conclusions

• IETF protocols will be extensively used for 3GPP-non-3GPP mobility in UMTS Rel8

PMIPv6, DSMIPv6 and MIPv4 in FA mode

• Some open issues still need to be resolved/clarifiedmobility mode selection (PMIPv6, DSMIPv6 and MIPv4 in FA mode)multihoming (i.e. multiple interface) managementsimultaneous usage of multiple access technologies for load-sharing or performance optimizationcombined usage of PMIPv6 and DSMIPv6 in case the UE moves into an access network that does not support any mobility feature (e.g. domestic/public WiFi access)handover optimizations for tight interworking with mobile WiMAXand/or CDMA2000