Network Working Group T. Dreibholz Internet-Draft SimulaMet Intended status: Informational J. Pulinthanath Expires: 3 April 2025 University of Duisburg-Essen 30 September 2024 Applicability of Reliable Server Pooling for SCTP-Based Endpoint Mobility draft-dreibholz-rserpool-applic-mobility-36 Abstract This document describes a novel mobility concept based on a combination of SCTP with Dynamic Address Reconfiguration extension and Reliable Server Pooling (RSerPool). 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." This Internet-Draft will expire on 3 April 2025. Copyright Notice Copyright (c) 2024 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. Dreibholz & Pulinthanath Expires 3 April 2025 [Page 1] Internet-Draft SCTP Mobility with RSerPool September 2024 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Existing Mobility Solutions . . . . . . . . . . . . . . . . . 2 2.1. Mobile IP and Mobile IPv6 . . . . . . . . . . . . . . . . 2 2.2. SCTP with Dynamic Address Reconfiguration . . . . . . . . 3 3. Solutions for Simultaneous Handovers . . . . . . . . . . . . 3 3.1. SCTP with Add-IP and Mobile-IP . . . . . . . . . . . . . 3 3.2. SCTP with Add-IP and RSerPool . . . . . . . . . . . . . . 4 4. Reference Implementation . . . . . . . . . . . . . . . . . . 4 5. Testbed Platform . . . . . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 8.1. Normative References . . . . . . . . . . . . . . . . . . 5 8.2. Informative References . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction An increasing amount of Internet devices is getting mobile. Therefore, there is a growing demand for software solutions allowing for a seamless handover of communication sessions between multiple networks, e.g. to allow for a laptop or PDA to use a fast Ethernet connection when available, hand over to a WLAN when moving and hand over again to UMTS when the WLAN becomes unreachable - without interrupting the running communication sessions. Mobility handling is a deficiency of the common IP-based networks. Most of the available solutions are based on the network layer. The disadvantage of such solutions is that fundamental changes in the network infrastructure are needed. Therefore, we propose a new solution based on the upper layers to overcome these disadvantages. In this document, we present our mobility solution based on the SCTP protocol with Dynamic Address Reconfiguration extension and Reliable Server Pooling (RSerPool). 2. Existing Mobility Solutions 2.1. Mobile IP and Mobile IPv6 In the concept of Mobile IP [4] every node must register to a Home- Agent (HA) in its own home network. Then, the nodes are reachable under their home addresses managed by the HA. When a node leaves its home network, it must also register at a Foreign Agent (FA) in the new network. After that, a tunnel is established between the HA and the FA. Any traffic to the mobile node is then tunnelled by its HA to the FA and forwarded by the FA to the node itself. Clearly, the Dreibholz & Pulinthanath Expires 3 April 2025 [Page 2] Internet-Draft SCTP Mobility with RSerPool September 2024 detour of all traffic via HA and FA is inefficient and results in an increased transmission delay. Mobile IPv6 [5] is an extension of Mobile IP. In Mobile IPv6, the FA is not needed. The packets will be tunnelled from the HA to the Gateway Router in the foreign network, which forwards the packets to the endpoint. The inefficiency due to the detour of traffic as described for Mobile IP remains. 2.2. SCTP with Dynamic Address Reconfiguration Using the SCTP protocol (see [2] together with its Dynamic Address Reconfiguration extension (Add-IP, see [3]), it is possible for a mobile endpoint to inform its peer on address changes. That is, when a moving mobile client gets in the vicinity of an additional radio station, it sends an "ASCONF Add Address Request" to tell its peer that it is now reachable under an additional network-layer address. After that, the peer endpoint can use this additional address for a new SCTP path. When the first radio station becomes unreachable, the node can send an "ASCONF Delete Address Request" to the peer endpoint. After that, the peer removes the corresponding SCTP path to the unusable network-layer address. The following two cases for handovers are possible: * Make-before-Break: An additional SCTP path can be used before the original path becomes unusable. This case is trivial, since there is a continuous connectivity. * Break-before-Make: The original SCTP path becomes unusable before a new SCTP path can be used. For the case that only one endpoint performs a handover procedure at the same time, the mobile endpoint can always use Add-IP to communicate its new address to its peer endpoint. However, when both endpoints perform a handover simultaneously, no endpoint is able to tell its corresponding peer the new address. 3. Solutions for Simultaneous Handovers 3.1. SCTP with Add-IP and Mobile-IP Using SCTP with Add-IP and Mobile IP/Mobile IPv6, the ASCONF messages will be sent to the home address of the peer node. That is, even when both nodes are mobile, each endpoint is able to reach its peer endpoint using the corresponding home address. However, this solution still requires the full Mobile IP/Mobile IPv6 infrastructure. Dreibholz & Pulinthanath Expires 3 April 2025 [Page 3] Internet-Draft SCTP Mobility with RSerPool September 2024 3.2. SCTP with Add-IP and RSerPool Using RSerPool (see [1], [6], [7], [8], [9], [10], [11], at least one node registers as a Pool Element (PE) at an ENRP server under a Pool Handle (PH) known to both endpoints. Upon handover, it is simply necessary for the PE endpoint to re-register, i.e. to update its registration with its new address. The other endpoint can - in the role of a Pool User (PU) - ask an ENRP server for its peer node's new addresses. After the new address is known, it is able to create a new SCTP path and continue the communication. The usage of RSerPool to provide support for mobile endpoints provides the following advantages: * Simplicity: No Mobile IP/Mobile IPv6 infrastructure is needed. In particular, it is not necessary that the providers of used networks (e.g. public WLAN access points, UMTS providers, etc.) provide any support for the mobility solution. * Efficiency: No tunnelling of traffic is necessary. * Applicability: All major SCTP implementations already support the Dynamic Address Reconfiguration extension. It is only necessary to provide support for RSerPool, e.g. in the form of a userspace library, which is much easier to deploy than kernel extensions. * Flexibility: RSerPool provides a complete session layer. That is, providing applications on top of RSerPool makes the support for high availability simple. A more detailed description of our approach for endpoint mobility, as well as a performance analysis using a prototype implementation, can be found in our paper [16]. 4. Reference Implementation The RSerPool reference implementation RSPLIB can be found at [18]. It supports the functionalities defined by [6], [7], [8], [9] and [11] as well as the options [12], [14] and [13]. An introduction to this implementation is provided in [15]. 5. Testbed Platform A large-scale and realistic Internet testbed platform with support for the multi-homing feature of the underlying SCTP protocol is NorNet. A description of NorNet is provided in [17], some further information can be found on the project website [19]. Dreibholz & Pulinthanath Expires 3 April 2025 [Page 4] Internet-Draft SCTP Mobility with RSerPool September 2024 6. Security Considerations Security considerations for RSerPool systems are described by [10]. 7. IANA Considerations This document introduces no additional considerations for IANA. 8. References 8.1. Normative References [1] Tuexen, M., Xie, Q., Stewart, R., Shore, M., Ong, L., Loughney, J., and M. Stillman, "Requirements for Reliable Server Pooling", RFC 3237, DOI 10.17487/RFC3237, January 2002, . [2] Stewart, R., Ed., "Stream Control Transmission Protocol", RFC 4960, DOI 10.17487/RFC4960, September 2007, . [3] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M. Kozuka, "Stream Control Transmission Protocol (SCTP) Dynamic Address Reconfiguration", RFC 5061, DOI 10.17487/RFC5061, September 2007, . [4] Perkins, C., Ed., "IP Mobility Support for IPv4, Revised", RFC 5944, DOI 10.17487/RFC5944, November 2010, . [5] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July 2011, . [6] Lei, P., Ong, L., Tuexen, M., and T. Dreibholz, "An Overview of Reliable Server Pooling Protocols", RFC 5351, DOI 10.17487/RFC5351, September 2008, . [7] Stewart, R., Xie, Q., Stillman, M., and M. Tuexen, "Aggregate Server Access Protocol (ASAP)", RFC 5352, DOI 10.17487/RFC5352, September 2008, . Dreibholz & Pulinthanath Expires 3 April 2025 [Page 5] Internet-Draft SCTP Mobility with RSerPool September 2024 [8] Xie, Q., Stewart, R., Stillman, M., Tuexen, M., and A. Silverton, "Endpoint Handlespace Redundancy Protocol (ENRP)", RFC 5353, DOI 10.17487/RFC5353, September 2008, . [9] Stewart, R., Xie, Q., Stillman, M., and M. Tuexen, "Aggregate Server Access Protocol (ASAP) and Endpoint Handlespace Redundancy Protocol (ENRP) Parameters", RFC 5354, DOI 10.17487/RFC5354, September 2008, . [10] Stillman, M., Ed., Gopal, R., Guttman, E., Sengodan, S., and M. Holdrege, "Threats Introduced by Reliable Server Pooling (RSerPool) and Requirements for Security in Response to Threats", RFC 5355, DOI 10.17487/RFC5355, September 2008, . [11] Dreibholz, T. and M. Tuexen, "Reliable Server Pooling Policies", RFC 5356, DOI 10.17487/RFC5356, September 2008, . [12] Dreibholz, T., "Handle Resolution Option for ASAP", Work in Progress, Internet-Draft, draft-dreibholz-rserpool- asap-hropt-29, 6 September 2021, . [13] Dreibholz, T. and X. Zhou, "Definition of a Delay Measurement Infrastructure and Delay-Sensitive Least-Used Policy for Reliable Server Pooling", Work in Progress, Internet-Draft, draft-dreibholz-rserpool-delay-28, 6 September 2021, . [14] Dreibholz, T. and X. Zhou, "Takeover Suggestion Flag for the ENRP Handle Update Message", Work in Progress, Internet-Draft, draft-dreibholz-rserpool-enrp-takeover-26, 6 September 2021, . 8.2. Informative References [15] Dreibholz, T., "Reliable Server Pooling – Evaluation, Optimization and Extension of a Novel IETF Architecture", 7 March 2007, . Dreibholz & Pulinthanath Expires 3 April 2025 [Page 6] Internet-Draft SCTP Mobility with RSerPool September 2024 [16] Dreibholz, T., Jungmaier, A., and M. Tüxen, "A New Scheme for IP-based Internet Mobility", Proceedings of the 28th IEEE Local Computer Networks Conference (LCN) Pages 99-108, ISBN 0-7695-2037-5, DOI 10.1109/LCN.2003.1243117, 22 October 2003, . [17] Dreibholz, T. and E. G. Gran, "Design and Implementation of the NorNet Core Research Testbed for Multi-Homed Systems", Proceedings of the 3nd International Workshop on Protocols and Applications with Multi-Homing Support (PAMS) Pages 1094-1100, ISBN 978-0-7695-4952-1, DOI 10.1109/WAINA.2013.71, 27 March 2013, . [18] Dreibholz, T., "Thomas Dreibholz's RSerPool Page", 2022, . [19] Dreibholz, T., "NorNet – A Real-World, Large-Scale Multi- Homing Testbed", 2022, . Authors' Addresses Thomas Dreibholz Simula Metropolitan Centre for Digital Engineering Pilestredet 52 0167 Oslo Norway Email: dreibh@simula.no URI: https://www.simula.no/people/dreibh Jobin Pulinthanath University of Duisburg-Essen, Institute for Experimental Mathematics Ellernstraße 29 45326 Essen Germany Email: jp@iem.uni-due.de.de Dreibholz & Pulinthanath Expires 3 April 2025 [Page 7]