Network Working Group G. Chen Internet-Draft H. Deng Intended status: Informational China Mobile Expires: April 24, 2014 D. Michaud Rogers Communications J. Korhonen Renesas Mobile M. Boucadair France Telecom A. Vizdal Deutsche Telekom AG C. Byrne T-Mobile USA October 21, 2013 IPv6 Roaming Behavior Analysis draft-chen-v6ops-ipv6-roaming-analysis-01 Abstract This document intends to enumerate failure cases when a IPv6 subscriber roams into visited network areas. The investigations on those failed cases reveal the causes in order to notice improper configurations, equipment's incomplete functions or inconsistent IPv6 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 April 24, 2014. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. Chen, et al. Expires April 24, 2014 [Page 1] Internet-Draft ipv6-roaming October 2013 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 Descriptions . . . . . . . . . . . . . . 3 3. Roaming Scenario Overview . . . . . . . . . . . . . . . . . . 4 4. Failure Cases with Dual-stack Requests . . . . . . . . . . . 5 4.1. Failure Case 1: Roaming to IPv4-only networks . . . . . . 5 4.2. Failure Case 2: Roaming to early dual-stack networks . . 6 4.3. Failure Case 3: Roaming to IPv6-only networks . . . . . . 6 5. Failure Cases with IPv6-only Requests . . . . . . . . . . . . 6 5.1. Failure Case 4: Roaming to IPv4-only networks . . . . . . 6 5.2. Failure Case 5: Roaming to IPv6-only or dual-stack networks with 464xlat . . . . . . . . . . . . . . . . . . 7 6. Discussions . . . . . . . . . . . . . . . . . . . . . . . . . 7 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 8. Security Considerations . . . . . . . . . . . . . . . . . . . 8 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 10.1. Normative References . . . . . . . . . . . . . . . . . . 8 10.2. Informative References . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 1. Introduction IPv6 has been deployed globally to overcome the IPv4 depletion. Operators likely start or plan to upgrade the networks that allow IPv6 subscribers to access. As the dramatical uses of Internet services with a mobile access, IPv6 is an essential part to be considered in the mobile network evolution. 3rd Generation Partnership Project (3GPP) published the IPv6 migration guidance [TR23.975], which describes different technical evolution paths. In general, 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 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 Chen, et al. Expires April 24, 2014 [Page 2] Internet-Draft ipv6-roaming October 2013 analyze the causes. It's expected that operators could notice the issues and prevent potential risks. 2. Roaming Architecture Descriptions When a mobile device 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). There are two cases related to the roaming behavior. o International roaming: a mobile subscriber may entry a visited network, where different PLMN identity is used. The subscribers could either in an automatic mode or a manual mode to attach a PLMN cell. o Intra-PLMN mobility: a subscriber 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 attaches to the network, the subscriber profile should be traced from the home network for the network registration. When the visited network receives the registration requests from a subscriber, it should contact the home network and request the subscriber profile from Home Location Register(HLR) or Home Subscriber Server (HSS). Once the registration process is completed, the traffic flows may transmitted differently according to the subscriber data configuration. Two modes have been shown in the figure to illustrate the traffic flow paths, that are "Home routed traffic" and "Local breakout". +---------------------------------+ +------------------------+ |Visited Network | |Home Network | | +----+ +--------+ | | +--------+ Traffic Flow | | UE |==========>|SGSN/SGW|======================>|GGSN/PGW|============> | +----+ +--------+ | Signa ling | +--------+ | | |-------------------------->+--------+ | | | | |HLR/HSS | | | | | +--------+ | +---------------------------------+ +------------------------+ Figure 1: Home Routed Traffic In the home routed mode, subscribers will get addresses 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 IMS cases. Chen, et al. Expires April 24, 2014 [Page 3] Internet-Draft ipv6-roaming October 2013 +---------------------------------+ +------------------------+ |Visited Network | |Home Network | | +----+ +--------+ | Signaling | +--------+ | | | UE |==========>|SGSN/SGW|---------------------->|HLR/HSS | | | +----+ +--------+ | | +--------+ | | || | | | | +--------+ | | | | |GGSN/PGW| | | | | +--------+ | | | | Traffic Flow || | | | +-----------------------||--------+ +------------------------+ \/ Figure2: Local Breakout In the local breakout mode, the subscriber address will be assigned in 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. There are several usages for the local breakout mode. o Operators may add the APN-OI-Replacement flag[TS29.272] into user's subscription-data. The visited network could indicate the domain name to replace the user requested Access Point Name (APN). As a consequence, the traffic would be steered to the visited network. Those functions 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[TS23401] 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. 3. Roaming Scenario Overview 3GPP specified three types of Packet Data Protocol (PDP)/Packet Data Networks (PDN) to describe each connection, i.e. IPv4 PDP/PDN, IPv6 PDP/PDN and IPv4v6 PDP/PDN. Those PDP/PDN types should also be restored in Home Subscriber Server (HSS) as a part of subscriber Chen, et al. Expires April 24, 2014 [Page 4] Internet-Draft ipv6-roaming October 2013 profile. When a subscriber roams to a visited network, the new visited network notices that it is not registered with its own system, and attempts to identify its home network. Afterwards, the visited network will contact the home network and request the subscriber profile from HSS. In this process, service may be provided in a home routed or local breakout mode. The IP address can be allocated from home network or visited network accordingly. There may be a mismatch between the subscriber request and network capability. The following table lists the potential failure cases. +-------------+-------------------+--------------+--------------+ | UE Request | Visited Network | Home routed |Local Breakout| | | Capability | | | +-------------+-------------------+--------------+--------------+ | Dual stack | IPv4-only |Failure case 1|Failure case 1| +-------------+-------------------+--------------+--------------+ | Dual stack |IPv4-only/IPv6-only| OK |Failure case 2| +-------------+-------------------+--------------+--------------+ | Dual stack | IPv6-only | OK |Failure case 3| +-------------+-------------------+--------------+--------------+ | IPv6-only | IPv4-only | OK |Failure case 4| +-------------+-------------------+--------------+--------------+ | IPv6-only | Dual stack | OK |Failure case 5| | with 464xlat| | | | +-------------+-------------------+--------------+--------------+ | IPv6-only | IPv6-only | OK |Failure case 5| | with 464xlat| | | | +-------------+-------------------+--------------+--------------+ | IPv4-only | Dual stack | OK | OK | +-------------+-------------------+--------------+--------------+ Table 1: Roaming Scenario Descriptions 4. Failure Cases with Dual-stack Requests 4.1. Failure Case 1: Roaming to IPv4-only networks A mobile host in a dual-stack network likely requests PDP/PDN type IPv4v6 to allocate address. Such PDP/PDN type should be understandable in the network nodes, including Serving GPRS Support Node(SGSN), Gateway GPRS Support Node(GGSN), Serving Gateway(SGW), PDN Gateway(PGW), Home Location Registrar(HLR) and Home Subscriber Server(HSS). When the subscriber roams to the IPv4 network, the visited SGSN or SGW has to communicate with HLR/HSS in the home land to retrieve the subscriber profile. The visited pre-R9 SGSN don't understand the IPv4v6 PDP attribute for dual-stack, thus it refuse the subscriber registration. Resolving the issue may request the deletion of a IPv4v6 PDP attribute in home HLR/HSS. That may Chen, et al. Expires April 24, 2014 [Page 5] Internet-Draft ipv6-roaming October 2013 restrict UEs only initiates IPv4 PDP or IPv6 PDP activation. As alternative, operators have to upgrade the visited SGSN and SGW to support the IPv4v6 feature. However, operator may didn't control the visited nodes which belong to different operators. 4.2. Failure Case 2: Roaming to early dual-stack networks Dual-stack capability can be provided in a early mobile network(i.e. Pre-Release 8 network) using separate PDP/PDN activations. That means a single IPv4 and IPv6 PDP/PDN to be initiated to allocate IPv4 and IPv6 address separately. A roaming subscriber with IPv4v6 PDP/ PDN type should change the request to two separated PDP/PDN messages of single IP version in order to achieve equivalent results. Some operators may turn off the function only allow one PDP/PDN is alive for each subscriber. For example, IPv6 PDP/PDN would be rejected if the subscriber has an active IPv4 PDP/PDN. Therefore, the subscriber may lost IPv6 connection in the visited network. Even the two parallel PDP/PDN activations are allowed, it will double the investment of core networks. It requires additional correlation of those two sessions of single IP version on the charging system. If there are Policy and Charging Rules Function(PCRF)/Policy and Charging Enforcement Function (PCEF) deployed, the system would treat IPv4 and IPv6 session as independent and perform different Quality of Service(QoS) policies. The subscriber may have unstable experiences due to different behaviors on each IP version connection. 4.3. Failure Case 3: Roaming to IPv6-only networks If the visited network is only IPv6 capable, a dual-stack subscriber can be assigned with IPv6 address. There is no IPv4 address returned. Several IPv4 applications can't work in this case as reported in [RFC6586]. A translation-based method, for example Bump- in-the-host (BIH)[RFC6535] and 464xlat[RFC6877] , may help to address the issue. Those techniques are superior in a IPv6 single-stack environment. Operators may automatically enable the function in a IPv6-only network and disable in a dual-stack or IPv4 network. 5. Failure Cases with IPv6-only Requests 5.1. Failure Case 4: Roaming to IPv4-only networks 3GPP specified the PDP/PDN type IPv6 as early as IPv4 type. Therefore, the IPv6 single PDP/PDN type has been well supported and interpretable in the 3GPP network nodes. When a subscriber requests IPv6 PDP/PDN type, the network should only return the expected IPv6 address. Otherwise, the request should be dropped and the error code should be sent to the user. Roaming to IPv4-only networks with IPv6 PDP/PDN request would fail to get addresses. A proper fallback is Chen, et al. Expires April 24, 2014 [Page 6] Internet-Draft ipv6-roaming October 2013 desirable however the behavior is implementation specific. 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. Those fallback mechanisms are deserved to be implemented timely. 5.2. Failure Case 5: Roaming to IPv6-only or dual-stack networks with 464xlat 464xlat[RFC6877] is proposed to address IPv4 compability 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 [I-D.ietf-behave-nat64-discovery-heuristic] to automatically discover NAT64 prefixes. Those behaviors depend on the network deployment, which may has three possibilities, i.e. DNS64/NAT64, NAT64 and non-NAT64. In those cases, the mobile terminal could only use DNS64[RFC6147] to detect the existence of NAT64. The alternative way is to manually configure the NAT64 prefix or Well-Known Prefix (i.e. 64:ff9b::/96)[RFC6052]. However, those configurations may mismatch the status of visited networks. Considering the various network's situations, operators may adopt 464xlat in the home networks and use IPv4-only in the roaming networks. 6. Discussions 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 attachment from dual-stack subscribers in the case of LTE to 3G and IPv6-enabled 3G to IPv4 3G. It may be unsolvable unless all the interworking nodes(i.e. SSGN and SGW) have been upgraded to support IPv4v6 PDP/PDN type. Conversely, a user profile with IPv4-only PDP or IPv6 only PDP may temporarily get easy through roaming areas. Some operators may choose IPv6 PDP/PDN along with 464xlat in the home network to advance IPv6 deployment. Since IPv6 PDP/PDN has been introduced in 3GPP early release, it didn't require upgrading on the interworking nodes to parse such IPv6 PDP/PDN type. But it requires IPv4 fallback should be supported either on the mobile terminal or network equipments. Therefore, there is no working solution other than IPv4 to guarantee roaming if roaming has to be enabled. Chen, et al. Expires April 24, 2014 [Page 7] Internet-Draft ipv6-roaming October 2013 In general, home routed is the default mode for international roaming cases. Local breakout or SIPTO may be only considered for some specific services, for example IMS roaming or intra-PLMN mobility optimization. Therefore, the most roaming scenairos may take less risks if the host only initiate IPv4 or IPv6 PDP/PDN other than extended IPv4v6 PDP/PDN for the time being. 7. IANA Considerations This document makes no request of IANA. 8. Security Considerations The draft didn't introduce additional security concerns to the networks. 9. Acknowledgements The authors would like to thank V6ops chairs(Fred Baker and John Brzozowski) to encourage us to continue the work. This document is the result of the IETF V6ops IPv6-Roaming design team effort. 10. References 10.1. Normative References [I-D.ietf-behave-nat64-discovery-heuristic] Savolainen, T., Korhonen, J., and D. Wing, "Discovery of the IPv6 Prefix Used for IPv6 Address Synthesis", draft- ietf-behave-nat64-discovery-heuristic-17 (work in progress), April 2013. [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. Chen, et al. Expires April 24, 2014 [Page 8] Internet-Draft ipv6-roaming October 2013 [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. 10.2. Informative References [IR.65] , "IMS Roaming & Interworking Guidelines", May 2012. [RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X. Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, October 2010. [RFC6586] Arkko, J. and A. Keranen, "Experiences from an IPv6-Only Network", RFC 6586, April 2012. [TR23.975] 3GPP, "IPv6 migration guidelines", June 2011. [TS23401] , "General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access", . [TS29.272] , "Mobility Management Entity (MME) and Serving GPRS Support Node (SGSN) related interfaces based on Diameter protocol", . Authors' Addresses Gang Chen China Mobile 53A,Xibianmennei Ave., Xuanwu District, Beijing 100053 China Email: phdgang@gmail.com Chen, et al. Expires April 24, 2014 [Page 9] Internet-Draft ipv6-roaming October 2013 Hui Deng China Mobile 53A,Xibianmennei Ave., Xuanwu District, Beijing 100053 China Email: denghui@chinamobile.com Dave Michaud Rogers Communications Email: Michaud@rci.rogers.com Jouni Korhonen Renesas Mobile Porkkalankatu 24 FIN-00180 Helsinki Finland Email: jouni.nospam@gmail.com Mohamed Boucadair France Telecom No.32 Xuanwumen West Street Rennes, 35000 France Email: mohamed.boucadair@orange.com Vizdal Ales Deutsche Telekom AG Tomickova 2144/1 Prague 4, 149 00 Czech Republic Email: ales.vizdal@t-mobile.cz Chen, et al. Expires April 24, 2014 [Page 10] Internet-Draft ipv6-roaming October 2013 Cameron Byrne T-Mobile USA Bellevue Washington 98105 USA Email: cameron.byrne@t-mobile.com Chen, et al. Expires April 24, 2014 [Page 11]