DMM Working Group Z.W. Yan Internet-Draft CNNIC Intended status: Informational J.F. Guan Expires: 3 July 2023 BUPT J.-H. Lee Sejong University T. Huang BUPT December 2022 Mobility Capability Negotiation as a 5G Mobility Pattern draft-yan-dmm-man-10 Abstract Mobility support is an important network capability for mobile node, and 5G introduces the Mobility Pattern used by the Access and Mobility Management Function (AMF) to optimize mobility support provided to the UE. More specific, The AMF determines and updates Mobility Pattern of the UE according to the subscription of the UE, statistics of the UE mobility, network local policy, and the UE assisted information, or any combination of them with the help of Network Data Analytics Function (NWDAF). Based on different requirements, multiple mobility management protocols have been developed under IPv6. However, different protocols have different functional requirements on the network element or the host and then a scheme should be used in order to support the negotiation and selection of adopted mobility management protocol when a host (or UE) accesses to a new network. Besides, Mobility restrictions should also be considerred especially in 5G. In this draft, this issue is analyzed. 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 https://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." Yan, et al. Expires 3 July 2023 [Page 1] Internet-Draft MCN-PS December 2022 This Internet-Draft will expire on 4 June 2023. Copyright Notice Copyright (c) 2022 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 (https://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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Motivations . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Possible Cases . . . . . . . . . . . . . . . . . . . . . . . 5 4. Protocol Selection Principles . . . . . . . . . . . . . . . . 11 5. General Procedure . . . . . . . . . . . . . . . . . . . . . . 11 6. Security Considerations . . . . . . . . . . . . . . . . . . . 12 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . 12 8.2. Informative References . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 1. Introduction In order to clearly analyze the possible cases and actual requirements, the following category labels of the mobility management protocols are defined: * Mobile IPv6 (MIPv6) protocol: the mobility management scheme based on [RFC6275]. * Proxy Mobile IPv6 (PMIPv6) protocol: the mobility management scheme based on [RFC5213]. * MIPv6 suit protocols: based on MIPv6, there are multiple extension protocols have been standardized. These protocols can be classified into two types: protocols for the function extension and protocols for the performance enhancement. The protocols for the function extension are proposed to support some specific scenarios or functions, such as Dual-stack Mobile IPv6 (DSMIPv6) [RFC5555] for mobility of the dual-stack nodes, Multiple Care-of- address (MCoA) [RFC5648] for hosts with multiple access interfaces Yan, et al. Expires 3 July 2023 [Page 2] Internet-Draft MCN-PS December 2022 and Network Mobility (NEMO) [RFC3963] for mobility of sub-network. The other type is proposed to enhance the performance of the mobility management, such as Fast Mobile IPv6 (FMIP6) [RFC5568] for fast handover, Hierarchical Mobile IPv6 (HMIPv6) [RFC5380] for hierarchical mobility optimization. In the MIPv6 suit protocols, location update is initiated by the host and the tunnel is also terminated at the host. * PMIPv6 suit protocols: in order to reduce the protocol cost and enhance the handover performance further, the network-based mobility management protocols were proposed and PMIPv6 was standardized as a basis. Based on PMIPv6, a series of its extensions were proposed, such as Dual-stack Proxy Mobile IPv6 (DS-PMIPv6) [RFC5844], and Distributed Mobility Management Proxy Mobile IPv6 (DMM-PMIPv6) [RFC7333]. Be different from the MIPv6 suit protocols, the location update in PMIPv6 suit protocols is triggered by the network entity and the tunnel is established between network entities. Then the host needs to do nothing about the signaling exchange during the movement, particularly, the mobility is transparent to the IP layer of the host. * Network-based protocols: generally, it means the mobility management protocols which do not require the involvement of the mobile node in order to accomplish mobility. It includes PMIPv6 suit protocols and other network-based solutions, such as GPRS Tunnelling Protocol (GTP) [TS.29274][TS.29281]. * Host-based protocols: generally, the mobility management protocols which require the involvement of the mobile node in order to accomplish mobility. It includes MIPv6 suit protocols and other host-based solutions, such as Host Identity Protocol (HIP) [RFC7401] and IKEv2 Mobility and Multihoming Protocol (MOBIKE) [RFC4555]. * AMF: Access and Mobility Management Function, is responsible for processing the control signaling between the User Equipment (UE) and the core network. It inherits the mobility management function and access control function. It is the most important control module in the 5G core network. It has the ability to process user registration requests, authenticate user identity, and when the UE sends the location movement, it handles the UE's location update and other functions. Note that, UE is a general expression of 5G to describe the terminal device, and it is similiar to the host in Internet. UE and host can be interchangeable in this draft. * Mobility Pattern: The Mobility Pattern is a concept that may be used by the AMF to characterise and optimise the UE mobility with the aid of Network Data Analytics Function (NWDAF) [TS.23.288]. Due to the uneven space-time distribution of mobile data traffic and frequent user switching in the 5G system, the 5G core network function still has the problem of unbalanced load. Especially, when the UE accesses the 5G communication system or the UE moves Yan, et al. Expires 3 July 2023 [Page 3] Internet-Draft MCN-PS December 2022 between 5G base stations, the access network needs to allocate the access and handover requests of the UE to the AMF to carry and process them. Allocating UEs to those with relatively large remaining resources can achieve load balancing of different AMFs, thereby effectively accelerating service response speed and improving the stability of the communication system. To characterise and optimise the mobility pattern of UE, the subscription of the UE, statistics of the UE mobility, network local policy, and UE assisted information, or any combination of them should be analyzed according to 5G specification [TS.23.501] . * Mobility Restriction: The Mobility Restriction provide the capability of restricting network access and mobility support of a host. The traditional mobility support protocols mainly focus on the interaction procedure between host and network by defining the related protocol sepcification, but ignore the management of mobility support policy which is an import issue to provide the mobility support service in realistic network. 5G specification [TS.23.501] have classified the mobility restrictions into RAT restriction, Forbidden Area, Service Area Restrictions, Core Network type restriction and Closed Access Group information. Therefore, the mobility capability negotiation should consider these restrictions for future deployment requirements. * Mobility Data Analytics: The Mobility Data Analytics is a concept derived from the NWDAF to provide the collection, storage, retrieval and analytics function of mobility related data, and it can be used to inference the mobility pattern for a given UE/host. The policies, principles, and algorithms of mobility capability negotiation can also be intergated into this function from the aspect of network management. Figure 1 illustrates the scopes of the above different category labels. +----------------+ +----------------+ | Network-based | | Host-based | |+--------------+| |+--------------+| ||PMIPv6 suit || ||MIPv6 suit || ||+------------+|| ||+------------+|| |||PMIPv6 ||| |||MIPv6 ||| ||+------------+|| ||+------------+|| |+--------------+| |+--------------+| +----------------+ +----------------+ Figure 1: Scopes of different protocol category labels Yan, et al. Expires 3 July 2023 [Page 4] Internet-Draft MCN-PS December 2022 In reality, the host-based protocols and network-based protocols will be co-existing and multiple protocol deamons will be configured on the network entities and host. That means a scheme is needed to support the negotiation and selection of mobility management protocol when the host accesses into a new access network initially or handover happens [Paper-CombiningMobilityStandards]. This document tries to present the principles for the protocol selection and analyze the possible scenarios which should be supported by the further solution. 2. Motivations As illustrated above, these protocols may co-exist in reality and simultaneously be used in an access network or even the same entity to support ubiquitous connection and mobility support in 5G. Due to their different requirements on the network entity or host, a scheme is needed to support the negotiation and selection of adopted mobility management protocol when the host accesses to a new network, as a implementation of Mobility Pattern. Generally, two problems should be solved: * What principles should be followed for the protocol negotiation and selection? * What procedure should be adopted for the protocol negotiation and selection? This scheme is needed because network entity and host may have different capabilities and preferences (may be decided by the capability and mobility pattern of the host). This scheme aims to guarantee that the optimum and most suitable protocol will be used, although the selection procedure and notification scheme can be implementation-dependent. 3. Possible Cases From both host and network aspects, their capabilities of mobility management may have multiple cases as shown in Figure 2. We mainly analyze that host and network support single protocol for clear description, if multiple protocols are supported simultaneously by the host or network side, multiple cases exist at the same time but the logic is same as that in the case with single protocol supported. Specifically, the following cases should be considered. 1) Network supports network-based protocol, host supports network- based protocol In this case, there are the following sub-cases: Yan, et al. Expires 3 July 2023 [Page 5] Internet-Draft MCN-PS December 2022 a) Host supports PMIPv6 suit protocol, Network supports PMIPv6 suit protocol * if host supports PMIPv6 and network supports PMIPv6, PMIPv6 is selected. * if host supports PMIPv6 and network supports extended PMIPv6 protocol, extended PMIPv6 protocol is selected if no host involvement is needed, otherwise the plain PMIPv6 is selected (we assume that the extension protocols are backward-compatible with the related plain protocol). * if host supports extended PMIPv6 protocol and network supports PMIPv6, PMIPv6 is selected (we assume that the extension protocols are backward-compatible with the related plain protocol). * if host supports extended PMIPv6 protocol and network supports extended PMIPv6 protocol, the identical extension protocol is selected, otherwise, PMIPv6 is selected (we assume that the extension protocols are backward-compatible with the related plain protocol). Yan, et al. Expires 3 July 2023 [Page 6] Internet-Draft MCN-PS December 2022 +-------------+-----------+--------------------------- + | | |PMIPv6 | | | |-----------------+----------+ |Network-based|PMIPv6 suit| |DS-PMIPv6 | | | | +----------+ | | |PMIPv6 extensions|FPMIPv6 | | | | +----------+ | | | |DMM-PMIPv6| | | | +----------+ | | | |... | | |-----------+-----------------+----------+ | | Others |GTP | | | |----------------------------+ | | |... | +-------------+-----------+----------------------------+ | | |MIPv6 | | | |-----------------+----------+ |Host-based |MIPv6 suit | |DS-MIPv6 | | | | +----------+ | | | |FMIPv6 | | | | +----------+ | | |MIPv6 extensions |HMIPv6 | | | | +----------+ | | | |NEMO | | | | +----------+ | | | |DMM-MIPv6 | | | | +----------+ | | | |... | | |-----------+-----------------+----------+ | | Others |HIP | | | |----------------------------+ | | |MOBIKE | | | |----------------------------+ | | |... | +-------------+-----------+----------------------------+ Figure 2: Possible capacities of host and network b) Host supports PMIPv6 suit protocol, Network supports other network-based protocol * if host supports PMIPv6 and network supports other network-based protocol, other network-based protocol is selected if no host involvement is needed, otherwise failure. * if host supports extended PMIPv6 protocol and network supports other network-based protocol, other network-based protocol is selected if no host involvement is needed, otherwise failure. Yan, et al. Expires 3 July 2023 [Page 7] Internet-Draft MCN-PS December 2022 c) Host supports other network-based protocol, Network supports PMIPv6 suit protocol * if host supports other network-based protocol and network supports PMIPv6, PMIPv6 is selected. * if host supports other network-based protocol and network supports extended PMIPv6 protocol, extended PMIPv6 protocol is selected if no host involvement is needed, otherwise failure. d) Host supports other network-based protocol, Network supports other network-based protocol * the identical protocol is selected, otherwise follow network capability if the protocols are different. 2) Network supports network-based protocol, host supports host-based protocol In this case, there are the following sub-cases: a) Host supports PMIPv6 suit protocol, Network supports MIPv6 suit protocol * if host supports PMIPv6 and network supports MIPv6, failure. * if host supports PMIPv6 and network supports extended MIPv6 protocol, failure. * if host supports extended PMIPv6 protocol and network supports MIPv6, failure. * if host supports extended PMIPv6 protocol and network supports extended MIPv6 protocol, failure. b) Host supports PMIPv6 suit protocol, Network supports other host- based protocol * if host supports PMIPv6 and network supports other host-based protocol, failure. * if host supports extended PMIPv6 protocol and network supports other host-based protocol, failure. c) Host supports other network-based protocol, Network supports MIPv6 suit protocol * if host supports other network-based protocol and network supports MIPv6, failure. * if host supports other network-based protocol and network supports extended MIPv6 protocol, failure. Yan, et al. Expires 3 July 2023 [Page 8] Internet-Draft MCN-PS December 2022 d) Host supports other network-based protocol, Network supports other host-based protocol * failure. 3) Network supports host-based protocol, host supports network-based protocol In this case, there are the following sub-cases: a) Host supports MIPv6 suit protocol, Network supports PMIPv6 suit protocol * if host supports MIPv6 and network supports PMIPv6, PMIPv6 is selected in default and MIPv6 is selected if host prefers it. * if host supports MIPv6 and network supports extended PMIPv6 protocol, extended PMIPv6 is selected in default, then PMIPv6 is selected with the lower priority and MIPv6 is selected if host prefers it. * if host supports extended MIPv6 protocol and network supports PMIPv6, PMIPv6 is selected in default, then extended MIPv6 protocol is selected if host prefers it and network also supports, otherwise MIPv6 is selected with the lowest priority. * if host supports extended MIPv6 protocol and network supports extended PMIPv6 protocol, extended PMIPv6 protocol is selected in default, then PMIPv6 is selected, then extended MIPv6 protocol is selected if host prefers and network also supports, otherwise MIPv6 is selected with the lowest priority. b) Host supports MIPv6 suit protocol, Network supports other network- based protocol * if host supports MIPv6 and network supports other network-based protocol, other network-based protocol is selected if no host involvement is needed, otherwise failure. * if host supports extended MIPv6 protocol and network supports other network-based protocol, other network-based protocol is selected if no host involvement is needed, otherwise failure. c) Host supports other host-based protocol, Network supports PMIPv6 suit protocol * if host supports other host-based protocol and network supports PMIPv6, PMIPv6 is selected in default, otherwise failure. * if host supports other host-based protocol and network supports extended PMIPv6 protocol, extended PMIPv6 protocol is selected if no host involvement is needed, otherwise failure. Yan, et al. Expires 3 July 2023 [Page 9] Internet-Draft MCN-PS December 2022 d) Host supports other host-based protocol, Network supports other network-based protocol * other network-based protocol is selected if no host involvement is needed, otherwise failure. 4) Network supports host-based protocol, host supports host-based protocol In this case, there are the following sub-cases: a) Host supports MIPv6 suit protocol, Network supports MIPv6 suit protocol * if host supports MIPv6 and network supports MIPv6, MIPv6 is selected. * if host supports MIPv6 and network supports extended MIPv6 protocol, MIPv6 is selected. * if host supports extended MIPv6 protocol and network supports MIPv6, MIPv6 is selected. * if host supports extended MIPv6 protocol and network supports extended MIPv6 protocol, the identical protocol is selected, otherwise MIPv6 is selected. b) Host supports MIPv6 suit protocol, Network supports other host- based protocol * if host supports MIPv6 and network supports other host-based protocol, failure. * if host supports extended MIPv6 protocol and network supports other host-based protocol, failure. c) Host supports other host-based protocol, Network supports MIPv6 suit protocol * if host supports other host-based protocol and network supports MIPv6, failure. * if host supports other host-based protocol and network supports extended MIPv6 protocol, failure. d) Host supports other host-based protocol, Network supports other host-based protocol * the identical other host-based protocol is selected, otherwise failure. 5) Network supports host-based protocol and network-based protocol, host supports host-based protocol and network-based protocol Yan, et al. Expires 3 July 2023 [Page 10] Internet-Draft MCN-PS December 2022 * follow the network based protocol in default if the host can support, otherwise select the protocol both network and host can support if host prefers. 4. Protocol Selection Principles Two different schemes may be used for the protocol negotiation and selection: host-initiated and network-initiated. Within the MIPv6/ PMIPv6 protocols, the priority of the function-extension protocols should be higher than the performance-enhancement protocols. Generally, the following principles should be followed: * In default: Network based scheme if it can be supported * Priority 0: Follw mobility restriction * Priority 1: Follow network capability * Priority 2: Follow host preference * Priority 3: Support the functional extensions * Priority 4: Support the performance enhancements 5. General Procedure The protocol negotiation may be included in the MN_ATTACH Function [MN-AR.IF] and the implementation may be based on a new signaling message or extended messages (e.g., ICMPv6, Diameter, and RADIUS). Besides these, some other protocols may also be used in some specified scenarios, such as extended IEEE 802.21 primitives. Then the selected protocol will be included as a parameter in AMF during the node handover. The general procedure for the protocol selection should be: * During initiation, network-based protocol may be used as a default mobility management protocol once the network supports it. * If the host prefers host-based protocols, a negotiation is executed to handover from network-based protocol to host-based protocol. * After initial attachment, a profile will be generated in the management store to record the selected or preferred protocol of this host. * When the handover happens, the network will check the selected or preferred protocol during the authentication process. But the network also needs to notify the host if the selected protocol cannot be supported herein. When the host accesses to the network, an authentication should be executed before the mobility management service is provided. In order to support the mobility management protocol selection, a new information should be recorded by the network after the successful Yan, et al. Expires 3 July 2023 [Page 11] Internet-Draft MCN-PS December 2022 authentication during the initial attachment. The newly introduced information in AMF shows the selected mobility management protocol and should be updated when the used protocol changes. 6. Security Considerations Generally, this function will not incur additional security issues. The detailed influence should be analyzed in the future. 7. IANA Considerations A new authentication option or other signaling message option may be used based on the specific implementation. 8. References 8.1. Normative References [MN-AR.IF] Laganier, J., Narayanan, S., and P. McCann, "Interface between a Proxy MIPv6 Mobility Access Gateway and a Mobile Node", draft-ietf-netlmm-mn-ar-if-03, February 2008. [RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A., Thubert, P., and RFC Publisher, "Network Mobility (NEMO) Basic Support Protocol", RFC 3963, DOI 10.17487/RFC3963, January 2005, . [RFC4555] Eronen, P. and RFC Publisher, "IKEv2 Mobility and Multihoming Protocol (MOBIKE)", RFC 4555, DOI 10.17487/RFC4555, June 2006, . [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., Chowdhury, K., Patil, B., and RFC Publisher, "Proxy Mobile IPv6", RFC 5213, DOI 10.17487/RFC5213, August 2008, . [RFC5380] Soliman, H., Castelluccia, C., ElMalki, K., Bellier, L., and RFC Publisher, "Hierarchical Mobile IPv6 (HMIPv6) Mobility Management", RFC 5380, DOI 10.17487/RFC5380, October 2008, . [RFC5555] Soliman, H., Ed. and RFC Publisher, "Mobile IPv6 Support for Dual Stack Hosts and Routers", RFC 5555, DOI 10.17487/RFC5555, June 2009, . Yan, et al. Expires 3 July 2023 [Page 12] Internet-Draft MCN-PS December 2022 [RFC5568] Koodli, R., Ed. and RFC Publisher, "Mobile IPv6 Fast Handovers", RFC 5568, DOI 10.17487/RFC5568, July 2009, . [RFC5648] Wakikawa, R., Ed., Devarapalli, V., Tsirtsis, G., Ernst, T., Nagami, K., and RFC Publisher, "Multiple Care-of Addresses Registration", RFC 5648, DOI 10.17487/RFC5648, October 2009, . [RFC5844] Wakikawa, R., Gundavelli, S., and RFC Publisher, "IPv4 Support for Proxy Mobile IPv6", RFC 5844, DOI 10.17487/RFC5844, May 2010, . [RFC6275] Perkins, C., Ed., Johnson, D., Arkko, J., and RFC Publisher, "Mobility Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July 2011, . [RFC7333] Chan, H., Ed., Liu, D., Seite, P., Yokota, H., Korhonen, J., and RFC Publisher, "Requirements for Distributed Mobility Management", RFC 7333, DOI 10.17487/RFC7333, August 2014, . [RFC7401] Moskowitz, R., Ed., Heer, T., Jokela, P., Henderson, T., and RFC Publisher, "Host Identity Protocol Version 2 (HIPv2)", RFC 7401, DOI 10.17487/RFC7401, April 2015, . [TS.23.288] "3GPP TS 23.288 (V17.3.0): Architecture enhancements for 5G System (5GS) to support network data analytics services", 3GPP TS 23.288, December 2021. [TS.23.501] "3GPP TS 23.501 (V17.0.0): System Architecture for 5G System; Stage 2", 3GPP TS 23.501, March 2021. [TS.29274] "3GPP Evolved Packet System (EPS); Evolved General Packet Radio Service (GPRS) Tunnelling Protocol for Control plane (GTPv2-C); Stage 3", 3GPP TS 29.274 8.10.0, June 2011. [TS.29281] "General Packet Radio System (GPRS) Tunnelling Protocol User Plane (GTPv1-U)", 3GPP TS 29.281 10.3.0, September 2011. 8.2. Informative References Yan, et al. Expires 3 July 2023 [Page 13] Internet-Draft MCN-PS December 2022 [Paper-CombiningMobilityStandards] Oliva, A., Soto, I., Calderón, M., Bernardos, C., and M. Sanchez, "The costs and benefits of combining different IP mobility standards", Computer Standards and Interfaces, February 2013. Authors' Addresses Zhiwei Yan CNNIC No.4 South 4th Street, Zhongguancun Beijing 100190 China Email: yan@cnnic.cn Jianfeng Guan BUPT No.10 Xitucheng Road, Haidian District Beijing 100876 China Email: jfguan@bupt.edu.cn Jong-Hyouk Lee Sejong University 209, Neungdong-ro, Gwangjin-gu Seoul 05006 Republic of Korea Email: jonghyouk@sejong.ac.kr Tao Huang BUPT No.10 Xitucheng Road, Haidian District Beijing 100876 China Email: htao@bupt.edu.cn Yan, et al. Expires 3 July 2023 [Page 14]