Network Working Group G. Chen Internet-Draft H. Deng Intended status: Informational China Mobile Expires: January 09, 2014 July 08, 2013 IPv6 Roaming Behavior Analysis draft-chen-v6ops-ipv6-roaming-analysis-00 Abstract This document intends to enumerate failed 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/. 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Chen & Deng Expires January 09, 2014 [Page 1] Internet-Draft ipv6-roaming July 2013 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Roaming Descriptions . . . . . . . . . . . . . . . . . . . . 2 3. Roaming Behaviors from a Dual-stack Network . . . . . . . . . 3 3.1. Roaming to IPv4-only networks with IPv4v6 requests . . . 3 3.2. Roaming to early dual-stack networks . . . . . . . . . . 3 3.3. Roaming to IPv6-only networks . . . . . . . . . . . . . . 4 4. Roaming Behaviors from a IPv6 Single-stack Network . . . . . 4 4.1. Roaming to IPv4-only networks . . . . . . . . . . . . . . 4 4.2. Roaming to IPv6-only or dual-stack networks with 464xlat 4 5. Discussions . . . . . . . . . . . . . . . . . . . . . . . . . 4 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 7. Security Considerations . . . . . . . . . . . . . . . . . . . 5 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 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 analyze the causes. It's expected that operators could notice the issues and prevent potential risks. 2. Roaming Descriptions A mobile subscriber likely entries some network areas, that may be dual-tack, IPv6 single-stack and IPv4 single-stack. The mobile terminal connecting to the network is formulated with a subscriber profile. 3GPP specified three type of Packet Data Protocol (PDP)/ Packet Data Networks (PDN) to describe each connection. That are IPv4 PDP/PDN, IPv6 PDP/PDN and IPv4v6 PDP/PDN. Therein, the IPv4 and IPv6 PDP/PDN has been implemented at the early equipments. IPv4v6 is only supported by Post-Release 8 equipments, which equip the feature Chen & Deng Expires January 09, 2014 [Page 2] Internet-Draft ipv6-roaming July 2013 just in recent years. Those PDP/PDN types should also be restored in Home Subscriber Server (HSS) as a part of subscriber profile. When the mobile device is turned on or is transferred via a handover to the network, this new visited network sees the device, notices that it is not registered with its own system, and attempts to identify its home network. Afterwards, the visited network would contact the home network and request the subscriber profile from HSS. Since the visited network has different IPv6 supports, there may be a mismatch between the subscriber requires and network capability. The following is like to document the failure cases. 3. Roaming Behaviors from a Dual-stack Network 3.1. Roaming to IPv4-only networks with IPv4v6 requests A mobile subscriber 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 SGSN(Serving GPRS Support Node), GGSN(Gateway GPRS Support Node), SGW(Serving Gateway), PGW(PDN Gateway), HLR(Home Location Registrar) and HSS(Home Subscriber Server). 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. Roaming with IPv4v6 type in the subscriber profile may cause issues because the visited SGSN/SGW can't parse the information. The subscriber is failed to register in this case. 3.2. 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 respectively. 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 PCRF(Policy and Charging Rules Function)/PCEF(Policy and Charging Enforcement Function) deployed, the system would treat IPv4 and IPv6 session as independent and perform different QoS (Quality of Service) policies. The subscriber may have unstable experiences due to different behaviors on each IP version connection. Chen & Deng Expires January 09, 2014 [Page 3] Internet-Draft ipv6-roaming July 2013 3.3. 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 retured. 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. 4. Roaming Behaviors from a IPv6 Single-stack Network 4.1. 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 desirable however the behavior is implementation specific. Android system solves the issue by setting the roaming APN(Access Point Name). 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 and standardized timely. 4.2. 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. 5. Discussions Chen & Deng Expires January 09, 2014 [Page 4] Internet-Draft ipv6-roaming July 2013 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 LTE(Long Term Evolution)/SAE(System Architecture Evolution) 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, some operators may choose IPv6 PDP/PDN to start the communications in home networks and always use IPv4 in the roaming area. 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. It may be a workable solution given some terminals already support the function. As an alternative solution for dual-stack, operators may change a unified PDP/PDN request into two separated single IP version requests. However, this approach is problematic in the Charging records and QoS policy enforcement. In addition, it doubles the PDP resource uses. It may be unappealing for the deployment. A roaming to IPv6-only network occurs when operators deploy IPv6 single-stack networks. A dual-stack terminal maybe like to experience the IPv6-single service in the visited network while it may only use IPv4 PDP/PDN type in the home network. For those requests, a dual-stack terminal is recommended to populate translation-based function to enable the IPv4 service compatibility. Those functions should be turned off properly when the terminals roam back to dual-stack or IPv4 network. 6. IANA Considerations This document makes no request of IANA. 7. Security Considerations The draft didn't introduce additional security concerns to the networks. Chen & Deng Expires January 09, 2014 [Page 5] Internet-Draft ipv6-roaming July 2013 8. References 8.1. 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. [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. 8.2. Informative References [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. Authors' Addresses Chen & Deng Expires January 09, 2014 [Page 6] Internet-Draft ipv6-roaming July 2013 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 Chen & Deng Expires January 09, 2014 [Page 7]