IFAST#24/2004.10.04/07

CDMA Packet Data Roaming eXchange

Guidelines

(Sept. 1724, 2004)

v5.23

Editor: Raymond Hsu, QUALCOMM Inc.,

1

Table of Contents

Acronyms

References

1. Introduction

2. General Requirements for CDMA Packet Data Roaming

2.1 Reference Model

2.1.1 Interface Xd

2.1.2 Interface Xa

2.1.3 Interface Xi

2.2 IP Addressing Requirement

2.3 IP Routing Requirement

2.4 Security Requirement

2.5 Quality of Service

2.6 Peering Requirement

2.7 Proxy AAA Requirement

3. Services of CDMA Packet Data Roaming

3.1 Network Connectivity and Interconnection

3.1.1 Network Connection Options

3.1.2 IP Addressing and Routing

3.1.3 CRX IP Transit Backbone

3.1.4 Autonomous System Number (ASN)

3.2 RADIUS Proxy Service

3.2.1 RADIUS Message Relay

3.2.3 Response for Abnormal RADIUS Messages

3.2.4 RADIUS Accounting (Raw UDR) Mediation

3.3 Roaming Scenarios

3.3.1 Simple IP Roaming

3.3.2 Mobile IP Roaming

3.4 Data Exchange Interface between third parties (CRXs)

3.5 Data Clearing and Settlement

3.5.1 UDR

3.5.2 Accounting Data Reconciliation

3.5.3 Accounting Data Conversion and Rating

3.5.4 Format and Adequacy check

3.5.5 Partner Pair Determination

3.5.6 UDR Accommodation

3.5.7 Currency

3.5.8 Time Basis

3.5.9 Rating Unit

3.5.10 Settlement Rate Table

3.6 Settlement Reporting

3.6.1 Web-based settlement Reports

3.7The requirements from Financial Settlement Provider

3.8The Financial Settlement Function

3.9 Central Peering Point

3.10The schedule of Peering Settlement

4. Service Level of CDMA Packet Data Roaming Network

4.1 Network Service Level Agreement (Network SLA)

4.1.1 Network SLA Coverage

4.1.2 Network QoS Specifications

4.2 Proxy AAA Service Level Agreements (Proxy AAA SLAs)

4.2.1 Proxy AAA SLA Coverage

4.2.2 Proxy AAA QoS Specifications

4.3 Data Clearing and Financial Settlement Service Level Agreements

4.4 Support

5. Service Migration to CDMA2000/GPRS Inter-standard Packet Data Roaming

5.1 Mobile Station Registration and SGSN Attachment

5.2 Bearer connectivity establishment

5.2.1 Reference Model 1 (GGSN at Home CDMA2000 Packet Data System)

5.2.2 Reference Model 2 (GGSN at CRX Provider)

5.3 Data Clearing and Settlement

6. Future Considerations

Appendix 1 – Carrier Specific Customisation

Appendix 2 – Reporting

Appendix 3 – IS-835-A RADIUS Attributes Table

Appendix 4 – Financial Information (Settlement Reports)

Appendix 5 – Invoices

Appendix 6 – Billing Cycle Example

Appendix 7 – Xb Interface

Appendix 8 –XML Schema for Xj Interface

List of Figures

Figure 1. CRX Reference Model

Figure 2. CRX Peering Reference Model......

Figure 3. Proxy AAA Message Flows......

Figure 4. CRX Data Clearing and Settlement Reference Model 1

Figure 5. CRX Data Clearing and Settlement Reference Model 2

Figure 6. An example of Accounting Data Reconciliation Exchange Timeline......

Figure 7. An example of UDR accommodation......

Figure 8. Settlement Rate Table (Sample)

Figure 9. CDMA2000/GPRS Roaming Reference Model 1......

Figure 10. Call Flow for CDMA2000/GPRS Roaming Reference Model 1......

Figure 11. CDMA2000/GPRS Roaming Reference Model 2......

Figure 12. Call Flow for CDMA2000/GPRS Roaming Reference Model 2 using Mobile IP...

Figure 13. Call Flow for CDMA2000/GPRS Roaming Reference Model 2 using Simple IP and L2TP tunnelling between the CRX provider and home CDMA2000 packet data system

Figure 14. Call Flow for CDMA2000/GPRS Roaming Reference Model 2 using Simple IP and VPN tunnelling between the CRX provider and home CDMA2000 packet data system

Figure 15. CDMA2000/GPRS Data Clearing and Settlement Reference Model 1

Figure 16. CDMA2000/GPRS Data Clearing and Settlement Reference Model 2

Figure 17. Billing Cycle Example......

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Acronyms

3DESTriple Data Encrypted Standard

AAAAuthentication, Authorization, Accounting

APNAccess Point Name

ASAutonomous System

ASCIIAmerican Standard Code for Information Interchange

ATMAsynchronous Transfer Mode

BGBorder Gateway

BGPBorder Gateway Protocol

BSIDBase Station Identifier

CDGCDMA Development Group

CDMACode Division Multiple Access

CDRCharging Data Record

CPECustomer Premises Equipment

CRXCDMA Roaming eXchange

DESData Encrypted Standard

DNSDomain Name System

ESPEncapsulating Security Payload

EV-DOEvolution - Data Optimized

FAForeign Agent

FRFrame Relay

GGSNGateway GPRS Support Node

GMTGreenwich Mean Time

GTPGPRS Tunnelling Protocol

HAHome Agent

IKEInternet Key Exchange

IMFInternational Monetary Fund

IMSIInternational Mobile Station Identity

IPInternet Protocol

IPLC International Private Leased Circuit

IPSecIP Security

IPv4Internet Protocol Version 4

L2TPLayer 2 Tunnel Protocol

LACL2TP Access Concentrator

LANLocal Area Network

LLCLeased Line Circuit

LNSL2TP Network Server

MIPMobile IP

NATNetwork Address Translation

NSName Server

PDSNPacket Data Serving Node

PPPPoint-to-Point Protocol

QoSQuality of Service

RADIUSRemote Authentication Dial In User Service

SGSNServing GPRS Support Node

SIPSimple IP

TAPTransferred Account Procedure

UDRUsage Data Record

UMTSUniversal Mobile Telecommunications System

VPNVirtual Private Network

WAPWireless Application Protocol

References

[1]GSMA PRD-IR34 “Inter-PLMN Backbone Guidelines”

[2] J-STD-038-B (3GPP2 X.S0023) “Network Interworking between GSM MAP and ANSI-41 MAP; Rev. B”

[3] IS-835-A (P.S0001-A-1) “CDMA2000 Wireless IP Network Standard”

[4] 3GPP TS 23.060 “General Packet Radio Service (GPRS); Service description; Stage 2 (Release 6)”

[5] 3GPP TS 29.061 “Interworking between the Public Land Mobile Network (PLMN) supporting packet based services and Packet Data Network (PDN) (Release 6)”

[6] 3GPP TS 29.200 “Signalling System No. 7; Mobile Application Part (MAP); Security signalling flows for the Ze interface”

[7] 3GPP TS 29.060 “GPRS Tunelling Protocol (GTP) across the Gn and Gp interfaces (Release 4)”

[8] 3GPP TS 32.015 “Call and Event Data for the Packet Switched (PS) Domain (Release 1999)”

[9] CDG, “Wireless Data Roaming Requirements and Implementation Guide, Phase 1”, Version 9.6

[10]ANSI X3.106, "American National Standard for Information Systems-Data Link Encryption", American National Standards Institute, 1983.

[11] RFC 2406, S. Kent, R. Atkinson, “IP Encapsulating Security Payload (ESP)”, IETF proposed standard, Nov. 1998.

[12] RFC 2409, D. Harkins, D. Carrel, “The Internet Key Exchange (IKE)”, IETF proposed standard, Nov. 1998.

[13] RFC 2865, C. Rigney, et. al., “Remote Authentication Dial In User Service (RADIUS)”, IETF draft standard, June 2000.

[14] RFC 2866, C. Rigney, “RADIUS Accounting”, IETF informational RFC, June 2000.

[15] RFC 2794, P. Calhoun, C. Perkins, “Mobile IP Network Access Identifier Extension for IPv4”, IETF proposed standard, March 2000.

[16] RFC 2002, C. Perkins, “IP Mobility Support”, IETF proposed standard, Oct. 1996.

[17] RFC 3012, C. Perkins, P. Calhoun, “Mobile IPv4 Challenge/Response Extensions”, IETF proposed standard, Nov. 2000.

1. Introduction

The purpose of this document is to introduce guidelines for CDMA2000 inter-carrier packet data roaming through use of a 3rd Party provider’s exchange hub. CDG Reference Document titled “Wireless Data Roaming Requirements and Implementation Guide” sets forth the general principles for CDMA2000 packet data roaming using a direct connection between two roaming partners. Carriers shall have two options in the future – to inter-connect directly with roaming partners or to leverage the services of 3rd Party service providers’ exchange hubs. This document defines the interfaces between the carrier and the 3rd Party provider(s) and how the 3rd Party service providers’ exchange hubs must perform. One objective is to ensure that 3rd Party providers will be prepared to offer commercial service to carriers prior to the end of Q3 2004.

The assumptions and scope for this document include the following:

  • IS-835-A is used as the baseline standard
  • A number of IP connection scenarios will be addressed
  • Simple IP
  • Mobile IP
  • The servingvisited operator will generate the billing accounting records required for retail billing. Generation of retail billing not based on RADIUS accounting recordsrecords that are not RADIUS based will not be addressed.
  • Peering among 3rd Party providers shall be required.
  • 1xRTT shall be supported in this document. All The support of other air interface technologies within the CDMA2000 family of standards (e.g., 1xEV-DO) will be addressed in a future release of the document including EV-DO shall be supported.
  • CDMA2000 to CDMA2000 packet data roaming shall be defined initially, however this document shall also identify the hooks for follow-on CDMA2000 to GPRS service.

2. General Requirements for CDMA Packet Data Roaming

This section describes generic requirements for a 3rd Party to support CDMA packet data roaming. It specifies the reference model, the interface definition, IP addressing and routing, QoS, security as well as the peering requirement.

NOTE: This document is for IPv4 only. IPv6 is not included in this version of the guidelines.

2.1 Reference Model

CDMA Packet Data Roaming allows 3rd Party, i.e.,CDMA Roaming eXchange (CRX) Provider, to facilitate service between visited and home CDMA2000 packet data systems without requiring bilateral roaming (i.e., direct connectivity). The services, or service elements, defined in the guidelines include:

  • IP Data Transport
  • Authentication, Authorization, and Accounting (AAA)
  • RADIUS Data Clearing and Financial Net Settlement.

Figure 1Figure 1Figure 1 shows the interfaces between 3rd Party and CDMA2000 packet data systems, including visited and home, as well as the logical elements.

Figure 1. CRX Reference Model

Figure 1Figure 1Figure 1contains three interfaces:

  • Xd: IP layer interface for IP data transport
  • Xa: Application layer interface for Authentication, Authorization and Accounting (AAA) messages
  • Xi: Application layer interface for accounting data to data clearing system

Each interface in Figure 1Figure 1Figure 1, between a CDMA2000 packet data system and a 3rd Partyis a separate CDMA packet data roaming service.

The LAC and LNS functions are optional.

The operator may choose a subset of the services available from the3rd Party. For example, the operator may choose the 3rd party only for the data clearing service and rely on other IP data transport means (e.g., Internet).

2.1.1 Interface Xd

Interface Xd refers to the IP layer Interface between a CDMA2000 packet data system’s Border Gateway and the CRX provider’s Border Gateway. This interface carries traffic exchanged between a CDMA2000 packet data system and CRX provider, including

  • IP Routing Traffic
  • Tunnelling traffic between Visited and Home CDMA2000 packet data systems
  • L2TP tunnel traffic between LAC and LNS
  • MIP tunnel traffic between FA and HA.
  • AAA RADIUS traffic defined in interface Xa
  • Future traffic, such as
  • Interworking traffic
  • Tunnelling traffic for inter-standard roaming between GPRS/GSM (or GPRS/UMTS) and CDMA2000 packet data systems.

CDMA2000 packet data systems use the Xd Interface to access the CRX IP transport service. The access interface Xd must be implemented using either IPSec or Lease Line Circuit (LLC) to assure the lateral security. In addition to the firewalls required in the CDMA2000 packet data system, the CRX provider needs to maintain the firewall and filtering at the edge devices of the CRX provider network.

For the IP transit within the CRX provider, it is required to maintain all levels of security to ensure the security service.

2.1.2 Interface Xa

Interface Xa refers to the application interface between the CDMA2000 packet data system’s AAA server and CRX provider’s Proxy AAA server. This link carries authentication/authorization/accounting traffic between the Visited and Home CDMA2000 packet data systems.

The Proxy AAA servers in the CRX provider should route based on the realm of all RADIUS messages associated with roaming services, such as user authentication, authorization and accounting, and tunnel authentication.

The “Xa” interface can be offered as a bundled service with IP transport or as a Proxy-AAA only service from the CRX provider. For either case, AAA RADIUS traffic over the logical link in the Xa interface shall be carried through the physical Xd interface, with assured security guarantee,

The CRX provider may offer data clearing service using the raw UDR in RADIUS format between visited and home CDMA2000 packet data systems as part of packet data roaming service.

2.1.3 Interface Xi

The “Xi” Interface refers to the application layer interface, required to exchange raw UDR in RADIUS Accounting format with data-clearing service provider when visited and home CDMA2000 packet data systems select their respective CRX or data-clearing service providers for their packet data roaming services. This interface should only support RADIUS Accounting packets.

2.2 IP Addressing Requirement

A public IP address should be used for each service element that participates in the packet data roaming, including visited and home CDMA2000 packet data systems as well as CRX providers.

The elements requiring public IP address are:

  • PDSN/LAC and LNS,
  • PDSN/FA and HA,
  • AAA Sever and Proxy AAA Server,
  • Application servers[1] (e.g., WAP gateway, mail server, etc.),
  • Border Gateway.
  • Mobile Station1.

Using public addressing means that each party has a unique address space officially reserved from the Internet addressing authority. However, public addressing does not mean that these addresses should be visible to the Internet. These roaming service elements should remain invisible and inaccessible from the public Internet.

2.3 IP Routing Requirement

Each participating mobile network should exchange IP routing information with its CRX provider in order to route the IP packets between the CRX provider network and the CDMA2000 packet data system. The CRX providers should manage the IP routing information obtained from a particular CDMA2000 packet data system and is responsible for announcing it to other CDMA2000 packet data systems on behalf/request of that particular CDMA2000 packet data system. The home network does not need to exchange routing information with the visited systems directly.

BGP-4 IP routing protocol is recommended to dynamically exchange routing information between the Border Gateways of CRX provider and the CDMA2000 packet data systems via the “Xd” interface. Static routing is also feasible if BGP-4 protocol is not supported by the home network.

2.4 Security Requirement

In order to ensure the proper level of security within the packet data roaming infrastructure, the following requirements for CDMA2000 packet data systems and CRX providers are recommended:

  • Both CDMA2000 packet data systems and CRX providers should implement firewalls in the Border Gateways.
  • The IP addresses that are assigned to those service elements participating in the packet data roaming should be invisible (i.e., not routable) to the Internet.
  • The IPSec connections between CDMA2000 packet data systems and CRX providers are required if direct leased-line connections (e.g., FR, ATM, IPLC) are not available.

The CDMA2000 packet data systems and CRX providers together should be responsible for prevention of IP address spoofing.

2.5 Quality of Service

In order to maintain the required performance of network and application, Quality of Service (QoS) should be specified and offered by the CRX provider. The QoS definition consists of physical characteristics of the network level performance parameters (delay, packet loss, and jitter), and application level performance parameters (response time, and throughput)

In general, each service provided by the CRX provider should have its own QoS defined, such as QoS for IP data transport, for AAA Proxy, as well as for data clearing. The parameters defined in a QoS should be agreed upon between a CDMA2000 packet data system and its CRX provider jointly.

2.6 Peering Requirement

A CRX provider should arrange peering with other CRX providers directly so that any CDMA2000 packet data system connected to a CRX provider can reach any other CDMA2000 packet data system. A CRX provider should guarantee that its network is reliable and the traffic exchanged over Xd and Xa interfaces can be routed to CDMA2000 packet data systems connected to other CRX providers.

In addition to the QoS committed to its directly connected CDMA2000 packet data systems, CRX providers should define QoS among themselves to ensure the QoS across multiple CRX provider networks without compromising the end-to-end services.

It is recommended to have no more than two CRX providers between the visited and home CDMA2000 packet data systems. Figure 2Figure 2Figure 2shows the CRx peering reference model.

Figure 2. CRX Peering Reference Model

Central peering point refers to a common data exchange site where CRX providers can be physically interconnected to each other, e.g., using Ethernet, Fiber and ATM. This point is usually serviced by Telehouse[2] or InternetDataCenter. The selection of the central peering point should be agreed upon among the CRX providers. The criteria of central peering point should be agreed by the CRX providers. As a high level guideline, the basic criteria of selecting the central peering point include the following:

  • The central peering point service provider must be a neutral service provider (i.e., not associated with any CRX providers).
  • The traffic exchange via the switch used for the central peering should not be reachable to/from the public Internet.
  • The physical switch used for the central peering point should provide certain SLAs agreed by the CRX providers.
  • The central peering point service provider should allow the bilateral cross-connect between any CRX providers within the premises of the central point.
  • The central peering point service provider should provide monitoring and reporting to facilitate the traffic exchange.
  • The central peering point service provider should not allow transit peering (i.e., direct connectivity between a CDMA2000 packet data system and the central peering point).
  • The central peering point service provider must support static and dynamic routing.

2.7 Proxy AAA Requirement

The RADIUS protocol is a protocol used for exchanging authentication, authorization, and accounting information for CDMA2000 packet data services. The Proxy AAA Service offered as part of the packet data roaming services by the CRX provider should ensure a maximum interoperability among multiple AAA implementations. The requirements to do this are:

  • The Proxy AAA server should route all the RADIUS packets originated in the visited AAA to the home AAA, and vice versa.
  • The Proxy AAA server should support all the RADIUS attributes defined by IS-835-A.
  • The Proxy AAA server should not drop unknown RADIUS attributes if they are present in the RADIUS Accounting packets. Further study is needed to investigate the impact of ignoring the unknown RADIUS attributes in Access Request/Response packets.
  • The Proxy AAA server should route RADIUS packets to other Proxy AAA server under a peering agreement.
  • The Proxy AAA server should be allowed to respond to the RADIUS Access Request, based on the home operator's policy, if the Proxy AAA server cannot reach any of the AAA servers in the home CDMA packet data system.
  • The Proxy AAA server should be allowed to modify the RADIUS Accounting packets to meet certain proprietary service requirements.
  • The Proxy AAA server should be allowed to redistribute the RADIUS Accounting packets to non-CRX providers, such as a data clearing system, for further data processing and services.
  • In the event where the network identifier portion of the MSID (e.g., MIN, IMSI) does not correspond to the realm portion of the NAI in the RADIUS Access Request, the Proxy AAA server should be allowed to respond with the RADIUS Access Reject based on the home operator's policy.This may be useful for alleviating the home operator’s AAA server from unnecessary processing.
  • The Proxy AAA server should be allowed to rely on the network identifier portion of the MSID (e.g., MIN, IMSI) to route RADIUS messages. This requires the home operator to notify its MSID’s network identifiers to the CRX provider. This may be useful for a home operator whose subscribers use a common username but without the realm portion to identify the home operator.

3.Services of CDMA Packet Data Roaming

This section describes implementation requirements for services offered by the CRX provider. It covers the three service components: IP Data Transport, Proxy AAA, and RADIUS Data Clearing and Settlement.