Network Working Group G. Chen Internet-Draft H. Deng Intended status: Informational China Mobile Expires: July 17, 2014 D. Michaud Rogers Communications J. Korhonen Renesas Mobile M. Boucadair France Telecom A. Vizdal Deutsche Telekom AG C. Byrne T-Mobile USA January 13, 2014 IPv6 Roaming Behavior Analysis draft-ietf-v6ops-ipv6-roaming-analysis-00 Abstract This document identifies as set of failure cases encountered by an IPv6-enabled IPv6 customers in roaming scenarios. The investigations on those failed cases reveal the causes in order to notice improper configurations, equipment's incomplete functions or inconsistent IPv6 introduction strategy. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on July 17, 2014. Chen, et al. Expires July 17, 2014 [Page 1] Internet-Draft IPv6 Roaming Analysis January 2014 Copyright Notice Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Roaming Architecture Description . . . . . . . . . . . . . . 3 3. Roaming Scenario: Overview . . . . . . . . . . . . . . . . . 5 4. Failure Cases in the Attach Stage . . . . . . . . . . . . . . 6 5. Failure Cases in the IP Allocation Stage . . . . . . . . . . 7 5.1. Case 1: Splitting Dual-stack Bearer . . . . . . . . . . . 7 5.2. Case 2: Lack of IPv6 support in applications . . . . . . 8 5.3. Case 3: Fallback Incapability . . . . . . . . . . . . . . 8 5.4. Case 4: 464xlat Support . . . . . . . . . . . . . . . . . 9 6. Discussions . . . . . . . . . . . . . . . . . . . . . . . . . 9 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 8. Security Considerations . . . . . . . . . . . . . . . . . . . 10 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 10.1. Normative References . . . . . . . . . . . . . . . . . . 11 10.2. Informative References . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 1. Introduction Many Mobile Operators deployed or are in a per-deployment stage of IPv6 in their operational networks. Customers will be delivered with IPv6 connectivity if their UE (User Equipment) are IPv6-compliant. Many strategies can be adopted for IPv6 introduction in mobile networks (see for example [TR23.975]). A detailed overview of IPv6 support in 3GPP architectures is provided in [RFC6459]. Mobile Operators may deploy dual-stack or IPv6 single-stack depending on network's conditions. It has been observed that those deployments are rolled out in multiple provisioning domains. In the early IPv6 stage, a mobile subscriber roaming around the different areas may Chen, et al. Expires July 17, 2014 [Page 2] Internet-Draft IPv6 Roaming Analysis January 2014 experience service degradations or interruptions due to the inconsistent configurations and incomplete functions in the networks nodes. This memo intends to document the observed failed cases and analyze the causes. 2. Roaming Architecture Description The roaming process could be triggered in the following scenarios: o International roaming: a mobile UE may entry a visited network, where different PLMN (Public Land Mobile Network) identity is used. UEs could, either in an automatic mode or a manual mode, attach to the visited PLMN. o Intra-PLMN mobility: a UE moves to a visited network as that of the Home Public Land Mobile Network (HPLMN). However, the subscriber profiles may not be stored in the area. Once the subscriber attached to the network, the subscriber profile should be extracted from the home network for the network registration. When a UE is turned on or is transferred via a handover to a visited network, the mobile device will scan all radio channels and find available Public Land Mobile Networks (PLMNs) to attach. Serving GPRS Support Node (SGSN) or Mobility Management Entity (MME) in the visited networks must contact the Home Location Register(HLR) or Home Subscriber Server(HSS) and obtain the subscriber profile. Once the authentication and registration process is completed, the PDP activation and traffic flows may be operated differently according to the subscriber data configuration. Two modes have been shown at the figure to illustrate, that are "Home routed traffic" (Figure 1) and "Local breakout" (Figure 2). +---------------------------------+ +------------------------+ |Visited Network | |Home Network | | +----+ +--------+ | | +--------+ Traffic Flow | | UE |==========>|SGSN/MME|======================>|GGSN/PGW|============> | +----+ +--------+ | Signaling | +--------+ | | |-------------------------->+--------+ | | | | |HLR/HSS | | | | | +--------+ | +---------------------------------+ +------------------------+ Figure 1: Home Routed Traffic Chen, et al. Expires July 17, 2014 [Page 3] Internet-Draft IPv6 Roaming Analysis January 2014 +---------------------------------+ +------------------------+ |Visited Network | |Home Network | | +----+ +--------+ | Signaling | +--------+ | | | UE |==========>|SGSN/MME|---------------------->|HLR/HSS | | | +----+ +--------+ | | +--------+ | | || | | | | +--------+ | | | | |GGSN/PGW| | | | | +--------+ | | | | Traffic Flow || | | | +-----------------------||--------+ +------------------------+ \/ Figure 2: Local Breadkout In the home routed mode, subscribers will activate the PDP/PDN context and get address from the home network. All traffic would be routed back to the home networks. That is the default case for an international roaming except for the IP Multimedia Subsystem (IMS) scenario. In the local breakout mode, the subscriber address will be assigned from the visited network. The traffic flow would directly offloaded locally at a network node close to that device's point of attachment in the visited networks. Therefore, more efficient route would be achieved. The following will describe the cases where there is local breakout mode adopted. o Operators may add the APN-OI-Replacement flag defined in 3GPP [TS29.272] into user's subscription-data. The visited network indicates a local domain name to replace the user requested Access Point Name (APN). As the consequence, the traffic would be steered to the visited network. Those functions are normally deployed for the Intra-PLMN mobility cases. o Operators could also configure VPLMN-Dynamic-Address-Allowed flag[TS29.272] in the user profile to enable local breakout mode in Visited Public Land Mobile Networks (VPLMNs). o 3GPP specified Selected IP Traffic Offload (SIPTO) function[TS23.401] since Release 10 in order to get efficient route paths. It enables an operator to offload certain types of traffic at a network node close to that device's point of attachment to the access network. o GSMA has defined RAVEL[IR.65] as IMS international roaming architecture. Local breakout mode has been adopted for the roaming architecture. Chen, et al. Expires July 17, 2014 [Page 4] Internet-Draft IPv6 Roaming Analysis January 2014 3. Roaming Scenario: Overview 3GPP specifies three types of Packet Data Protocol (PDP)/Packet Data Networks (PDN) to describe connections: PDP/PDN Type IPv4, PDP/PDN Type IPv6 and PDP/PDN Type IPv4v6. When establishing a data session, user devices are configured to request a particular PDP/PDN Type. The allowed PDP/PDN types for a particular subscriber are stored in the Home Subscriber Server (HSS) or Home Location Register (HLR) as part of the subscriber profile as defined in [TS29.272]. When a subscriber roams and attempts to attach to a visited network, the visited network identifies the subscriber's home network. Afterwards, the visited network will contact the home network and request the subscriber profile from the home HSS/HLR. The subscriber profile contains the allowed Access Point Names (APN), allowed PDP/ PDN Types and policies regarding the routing of data sessions (i.e. home routed or local breakout mode). The failures are happened either in the initial network attach stage or the IP address allocation process due to the mismatch between the subscriber requested, allowed PDP/PDN Type and the visited network capability. The failures in the initial network process are likely occurred in both cases of home routed and the local breakout. The visited network may not be able to parse the subscription information containing the PDP/PDN Type IPv4v6, therefore it would reject the attach request from roaming subscribers. Section 4 provides the detailed discussion on the causes and known solutions. Even if roaming subscribers have a successful attach to the visited network, there are still some failures during the IP address allocation. Those failures are mainly appeared in the local breakout cases. The below table lists the potential cases. Section 5 makes further descriptions for the each case. Chen, et al. Expires July 17, 2014 [Page 5] Internet-Draft IPv6 Roaming Analysis January 2014 +-------------+-------------------+--------------+ | UE request | PDN/PDP IP Type |Local breakout| | | permitted | | +-------------+-------------------+--------------+ | IPv4v6 | IPv4 or IPv6 |Failure case 1| +-------------+-------------------+--------------+ | IPv4v6 | IPv6 |Failure case 2| +-------------+-------------------+--------------+ | IPv6 | IPv4 |Failure case 3| +-------------+-------------------+--------------+ | IPv6 | IPv6 |Failure case 4| | with 464xlat| without NAT64 | | +-------------+-------------------+--------------+ Table 1: Roaming Scenario Descriptions 4. Failure Cases in the Attach Stage 3GPP specified PDP/PDN type IPv4v6 into 3G network since Release 9. It allows a User Equipment (UE) to request both IPv4 and IPv6 within a single PDP/PDN request. This feature is stored as a part of subscription data for a subscriber in the Home Location Registrar(HLR) or Home Subscriber Server(HSS). It should be understandable to the Serving GPRS Support Node (SGSN) during the network attach process. However, operators may have different strategies to upgrade their network to support this new feature. If the home network populates the PDP/PDN type IPv4v6 in the subscription data and the visited network just stay as early as pre- Release 9, the failure is likely to be encountered. When a subscriber roams to an IPv4 network, the visited SGSN has to communicate with HLR/HSS in the home land to retrieve the subscriber profile. The issue we observe is that multiple SGSNs will be unable to correctly process a subscriber data received in the Insert Subscriber Data procedure[TS23.060] if it contains an Ext-PDP-Type defined in 3GPP [TS29.002]. As a consequence , it will likely refuse the subscriber attach request. Operators may have to remove the PDP/PDN type IPv4v6 from HLR/HSS in the home network, that will restrict UEs only initiates IPv4 PDP or IPv6 PDP activation. In order to avoid this situation, operators should make a comprehensive roaming agreement to support IPv6 and ensure that aligns with GSMA document, e.g [IR.33], [IR.88] and [IR.21]. Since the agreement requires visited operators to upgrade all SGSN nodes, some short- or medium-term solutions have been implemented to fix the issue. There are some specific configurations in HLS/HSS of home network. Multiple PDP/PDN subscription information will be added in the subscriber profiles, for example it Chen, et al. Expires July 17, 2014 [Page 6] Internet-Draft IPv6 Roaming Analysis January 2014 may include both PDP/PDN type IPv4 and PDP/PDN type IPv4v6 for a user profile. Once the HLR/HSS receives an Update Location message from visited SGSN, only the subscription data with PDP/PDN type IPv4 will be sent to SGSN/MME in the Insert Subscriber Data procedure. It guarantee the user profile could compatible with visited SGSN/MME capability. 5. Failure Cases in the IP Allocation Stage Once a subscriber succeed in the attach stage, IP allocation process is taken place to allocate IP addresses to the subscriber. This section has summarized several failures in the break-out cases. 5.1. Case 1: Splitting Dual-stack Bearer Dual-stack capability can be provided in a early mobile network (i.e. Pre-Release 8 network) using separate PDP/PDN activations. That means only a single IPv4 and IPv6 PDP/PDN is allowed to be initiated to allocate IPv4 and IPv6 address separately. The below demonstrates the cases. o The GGSN/PGW preferences dictate the use of IPv4 addressing only or IPv6 prefix only for a specific APN. o The SGSN/MME does not set the Dual Address Bearer Flag due to the operator using single addressing per bearer to support interworking with nodes of earlier releases A roaming subscriber with IPv4v6 PDP/PDN type have to change the request into two separated PDP/PDN requests with single IP version in order to achieve equivalent results. Some drawbacks in this case are listed as following: o The parallel PDP/PDN activations would likely double PDP/PDN resources consumptions. It impacts the capacity of GGSN/PGW, since a certain amount of PDP/PDN activations are only allowed on those nodes. o Some networks may only allow one PDP/PDN is alive for each subscriber. For example, IPv6 PDP/PDN will be rejected if the subscriber has an active IPv4 PDP/PDN. Therefore, the subscriber will lost IPv6 connection in the visited network. o Additional correlations between those two PDP/PDN contexts are required on the charging system. o Policy and Charging Rules Function(PCRF)/Policy and Charging Enforcement Function (PCEF) treat IPv4 and IPv6 session as Chen, et al. Expires July 17, 2014 [Page 7] Internet-Draft IPv6 Roaming Analysis January 2014 independent and perform different Quality of Service (QoS) policies. The subscriber may have unstable experiences due to different behaviors on each IP version connection. o Mobile devices may have the limitation of allowed simultaneous PDP /PDN activations. Overmuch PDP/PDN activation may result in other unrelated services broken. Operators may have to disable the local-break mode to avoid the risks. Another approach is to set a dedicated Access Point Name (APN) profile to only request IPv4 PDP/PDN type in the roaming network. 5.2. Case 2: Lack of IPv6 support in applications Some operators may adopt IPv6-only configuration for the IMS service, e.g. Voice over LTE(VoLTE)[IR.92] or Rich Communication Suite (RCS)[RCC.07]. Since IMS roaming architecture will offload all traffic in the visited network, a dual-stack subscriber can only be assigned with IPv6 address and no IPv4 address returned. It requires all the IMS based applications should be IPv6 capable. A translation-based method, for example Bump-in-the-host (BIH)[RFC6535] or 464xlat [RFC6877] may help to address the issue if there are IPv6 compatibility problems. Those functions could be automatically enabled in an IPv6-only network and disabled in a dual-stack or IPv4 network. 5.3. Case 3: Fallback Incapability 3GPP specified the PDP/PDN type IPv6 as early as PDP/PDN type IPv4. Therefore, the IPv6 single PDP/PDN type has been well supported and interpretable in the 3GPP network nodes. Roaming to IPv4-only networks with IPv6 PDP/PDN request could guarantee the subscription data is compatible with the visited pre-Release 9 SGSN. When a subscriber requests PDP/PDN type IPv6, the network should only return the expected IPv6 address. The mobile device may be failed to get IP address if the visited network only allocates an IPv4 address to a subscriber. In that case, the request will be dropped and the error code should be sent to the user. A proper fallback is desirable however the behavior is implementation specific. There are some mobile devices have the ability to provide a different configuration for home network and visited network respectively. It guarantees UE will always initiate PDP/PDN type IPv4 in the roaming area. Android system solves the issue by setting the roaming Access Point Name(APN). The mobile terminal is allowed to ignore the original requested protocol and always adhere to IPv4 when roaming. Chen, et al. Expires July 17, 2014 [Page 8] Internet-Draft IPv6 Roaming Analysis January 2014 5.4. Case 4: 464xlat Support 464xlat[RFC6877] is proposed to address IPv4 compatibility issue in a IPv6 single-stack environment. The function on a mobile terminal likely gets along with PDP/PDN IPv6 type request to cooperate with a remote NAT64[RFC6146] gateway. 464xlat may use the mechanism defined in [RFC7050] to automatically detect the presence of DNS64 and learn the IPv6 prefix used for protocol translation. When a mobile device with 464xlat function roams to an IPv6 visited network without the presence of NAT64 or DNS64, 464xlat may get failed to perform if traffic is undergoing the local breakout approach. The issue has been found mostly in a intra-PLMN mobility case. Considering the various network's situations, operators may turn off the local breakout and take home routed mode to perform 464xlat. Some devices may support the configuration to adopt 464xlat in the home networks and use IPv4-only in the visited networks with different roaming profile configurations. It could also be a solution to address this issue. 6. Discussions Several failure cases have been discussed in this memo. It has been testified the major issues are occurred at the two stages, i.e. the initial network attach and the IP allocation process. During the initial network attach, PDP/PDN type IPv4v6 is major concern to the visited pre-Release 9 SGSN. The dual-stack deployment is recommended in most cases. However, it may take some times in a mobile environment. 3GPP didn't specify PDP/PDN type IPv4v6 in the early release. Such PDP/PDN type is supported in new-built Long Term Evolution(LTE)/System Architecture Evolution(SAE) network, but didn't support well in the third generation network. The situations may cause the roaming issues dropping the attach request from dual-stack subscribers. Operators may have to adopt temporary solution unless all the interworking nodes(i.e. SSGN) in the visited network have been upgraded to support Ext-PDP-Type feature. The issues in the IP address allocation process are caused due to the local breakout policy. Since the IP address is allocated by the visited GGSN or PGW, the mismatch is found in the following aspects. o The mismatch between requested PDP/PDN type and permitted PDP/PDN type o The mismatch between application capability and allowed network connections Chen, et al. Expires July 17, 2014 [Page 9] Internet-Draft IPv6 Roaming Analysis January 2014 o The mismatch between mobile device function (e.g., 464xlat) and particular network deployment status There are some solutions to overcome the issue. Those solutions can be done either in the network side or mobile devices side. The below lists potential workarounds. o Change local breakout to the home routed mode o A dedicated roaming APN profile is implemented for roamer. When a subscriber roams to a visited network, PDP/PDN type IPv4 is always be selected for session activation. o Networks could deploy AAA server to coordinate the mobile device capability. Once the GGSN/PGW receive the session creation requests, it will initiate an Access-Request to an AAA server via the Radius protocol. The Access-Request contains subscriber and visited network information, e.g. PDP/PDN Type, International Mobile Equipment Id (IMEI), Software Version(SV) and visited SGSN/ MME location code, etc. The AAA server could take mobile device capability combining with the visited network information to ultimately determine the type of session to be created, i.e. IPv4, IPv6 or IPv4v6. 7. IANA Considerations This document makes no request of IANA. 8. Security Considerations Even if this document does not define a new architecture nor a new protocol, it is encouraged to refer to [RFC6459] for a generic discussion on IPv6-related security considerations. 9. Acknowledgements Many thanks to F. Baker and J. Brzozowski for their support. This document is the result of the IETF v6ops IPv6-Roaming design team effort. The authors would like to thank Mikael Abrahamsson, Victor Kuarsingh, Heatley Nick, Alexandru Petrescu and Tore Anderson for their helpful comments. Chen, et al. Expires July 17, 2014 [Page 10] Internet-Draft IPv6 Roaming Analysis January 2014 10. References 10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X. Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, October 2010. [RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful NAT64: Network Address and Protocol Translation from IPv6 Clients to IPv4 Servers", RFC 6146, April 2011. [RFC6147] Bagnulo, M., Sullivan, A., Matthews, P., and I. van Beijnum, "DNS64: DNS Extensions for Network Address Translation from IPv6 Clients to IPv4 Servers", RFC 6147, April 2011. [RFC6535] Huang, B., Deng, H., and T. Savolainen, "Dual-Stack Hosts Using "Bump-in-the-Host" (BIH)", RFC 6535, February 2012. [RFC6877] Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT: Combination of Stateful and Stateless Translation", RFC 6877, April 2013. [RFC7050] Savolainen, T., Korhonen, J., and D. Wing, "Discovery of the IPv6 Prefix Used for IPv6 Address Synthesis", RFC 7050, November 2013. 10.2. Informative References [IR.21] Global System for Mobile Communications Association, GSMA., "Roaming Database, Structure and Updating Procedures", July 2012. [IR.33] Global System for Mobile Communications Association, GSMA., "GPRS Roaming Guidelines", July 2012. [IR.65] Global System for Mobile Communications Association, GSMA., "IMS Roaming & Interworking Guidelines", May 2012. [IR.88] Global System for Mobile Communications Association, GSMA., "LTE Roaming Guidelines", January 2012. Chen, et al. Expires July 17, 2014 [Page 11] Internet-Draft IPv6 Roaming Analysis January 2014 [IR.92] Global System for Mobile Communications Association (GSMA), , "IMS Profile for Voice and SMS Version 7.0", March 2013. [RCC.07] Global System for Mobile Communications Association (GSMA), , "Rich Communication Suite 5.1 Advanced Communications Services and Client Specification Version 4.0", November 2013. [RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X. Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, October 2010. [RFC6459] Korhonen, J., Soininen, J., Patil, B., Savolainen, T., Bajko, G., and K. Iisakkila, "IPv6 in 3rd Generation Partnership Project (3GPP) Evolved Packet System (EPS)", RFC 6459, January 2012. [RFC6586] Arkko, J. and A. Keranen, "Experiences from an IPv6-Only Network", RFC 6586, April 2012. [TR23.975] 3rd Generation Partnership Project, 3GPP., "IPv6 migration guidelines", June 2011. [TS23.060] 3rd Generation Partnership Project, 3GPP., "General Packet Radio Service (GPRS); Service description; Stage 2 v9.00", March 2009. [TS23.401] 3rd Generation Partnership Project, 3GPP., "General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access v9.00", March 2009. [TS29.002] 3rd Generation Partnership Project, 3GPP., "Mobile Application Part (MAP) specification v9.00", December 2009. [TS29.272] 3rd Generation Partnership Project, 3GPP., "Mobility Management Entity (MME) and Serving GPRS Support Node (SGSN) related interfaces based on Diameter protocol v9.00", September 2009. Chen, et al. Expires July 17, 2014 [Page 12] Internet-Draft IPv6 Roaming Analysis January 2014 Authors' Addresses Gang Chen China Mobile 53A,Xibianmennei Ave., Xuanwu District, Beijing 100053 China Email: phdgang@gmail.com Hui Deng China Mobile 53A,Xibianmennei Ave., Xuanwu District, Beijing 100053 China Email: denghui@chinamobile.com Dave Michaud Rogers Communications 8200 Dixie Rd. Brampton, ON L6T 0C1 Canada Email: dave.michaud@rci.rogers.com Jouni Korhonen Renesas Mobile Porkkalankatu 24 FIN-00180 Helsinki, Finland Email: jouni.nospam@gmail.com Mohamed Boucadair France Telecom Rennes, 35000 France Email: mohamed.boucadair@orange.com Chen, et al. Expires July 17, 2014 [Page 13] Internet-Draft IPv6 Roaming Analysis January 2014 Vizdal Ales Deutsche Telekom AG Tomickova 2144/1 Prague 4, 149 00 Czech Republic Email: ales.vizdal@t-mobile.cz Cameron Byrne T-Mobile USA Bellevue Washington 98105 USA Email: cameron.byrne@t-mobile.com Chen, et al. Expires July 17, 2014 [Page 14]