Internet Engineering Task Force G. Chen Internet-Draft China Mobile Intended status: Informational C. Williams Expires: August 24, 2016 Consultant D. Wing A. Yourtchenko Cisco Systems, Inc. February 21, 2016 Happy Eyeballs Extension for Multiple Interfaces draft-ietf-mif-happy-eyeballs-extension-09 Abstract This memo proposes extensions to the Happy Eyeball(HE) defined in RFC6555 and fit into a multiple provisioning domain architecture. Happy Eyeballs in MIF would make the selection process smoother by using connectivity tests over pre-filtered interfaces according to defined policy. This would choose the most fast interface with an automatic fallback mechnism. 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 August 24, 2016. Copyright Notice Copyright (c) 2016 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 Chen, et al. Expires August 24, 2016 [Page 1] Internet-Draft happy-eyeballs-mif February 2016 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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Happiness Parameters . . . . . . . . . . . . . . . . . . . . 4 5. HE-MIF behavior . . . . . . . . . . . . . . . . . . . . . . . 5 5.1. First Step, Filter . . . . . . . . . . . . . . . . . . . 5 5.2. Second Step, Sort . . . . . . . . . . . . . . . . . . . . 6 6. Implementation Framework . . . . . . . . . . . . . . . . . . 7 7. Additional Considerations . . . . . . . . . . . . . . . . . . 7 7.1. Usage Scope . . . . . . . . . . . . . . . . . . . . . . . 7 7.2. Fallback Timeout . . . . . . . . . . . . . . . . . . . . 7 7.3. DNS Selections . . . . . . . . . . . . . . . . . . . . . 8 7.4. Flow Continuity . . . . . . . . . . . . . . . . . . . . . 9 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 9. Security Considerations . . . . . . . . . . . . . . . . . . . 9 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 11.1. Normative References . . . . . . . . . . . . . . . . . . 9 11.2. Informative References . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction In a multiple interface context, the problems raised by hosts with multiple interfaces have been discussed in the MIF problem statement [RFC6418], which describes the various issues when using a wrong domain selection on a MIF node. Happy Eyeballs (HE) [RFC6555] describes how a dual-stack client can determine the most fast path to a dual-stack server by employing a stateful algorithm to quickly discover if the IPv4 or IPv6 path is faster. while this is a good method to achieve smart path selection, it assumes a single-homed node targeted. Interaction with multiple interfaces was deferred for further study. [RFC7556] has proposed a multiple provisioning domain architecture. This memo proposes extensions to the Happy Eyeball(HE) defined in [RFC6555] to support multiple interfaces, such that a node with multiple interfaces can choose the most fast path for a particular connection-oriented flow (e.g., TCP, SCTP). Chen, et al. Expires August 24, 2016 [Page 2] Internet-Draft happy-eyeballs-mif February 2016 2. Terminology This document makes use of following terms: o Happy Eyeballs (HE): it specifies requirements for algorithms that reduce user-visible delay of dual-stack hosts within a single home. o HE-MIF: it adopts Happy Eyeballs concept [RFC6555] to the multiple provisioning domain architecture. It describes requirements for algorithms that offer connectivity tests on PVD-aware or non-PVD- aware nodes [RFC7556] to select the most fast interface. 3. Use Cases The section describes use cases in existing networks. Use Case: WiFi is broken Assuming a MIF node has both 3GPP mobile network interface and WiFi interface, a common practice would always prefer WiFi connection when the node enters a WiFi area. In this situation, a node might assume the WiFi link can reach destinations on the global Internet, because a valid IP address has been assigned on the interface. However, this might not be the case for several reasons, such as authentication requirements, instability at layer 2, or even, perhaps, the WiFi being connected to a local network with no global Internet reachability. In order to figure out the problems, a user has to turn off the WiFi manually. With HE-MIF, users can indicate their desire with some setting on the phone. For instance, they may prefer to wait an appropriate time slot but not forever. After the timer is expired, users may finally give up the WiFi path and try to establish connection over a 3GPP mobile network path. Users may not want a very short timer, because the mobile network path for most people is more expensive than a WiFi path. An appropriate timer is desired to balance user experience and expenditure. Use Case: Policy Conflict A node has both WiFi and 3GPP network access simultaneously. In a mobile network, IPv6-only may be preferable since IPv6 has the potential to be simpler than dual-stack. WiFi access still remains on IPv4. The problem is caused by source address selection principle [RFC6724] and wifi preference. The transition to IPv6 is likely to encourage and prefer IPv6 . If a 3GPP network path has IPv6 on it and a WiFi does not, the 3GPP interface might be chosen while it maybe a suboptimal selection since the wifi interface likely is less expensive. With HE-MIF, user's interests could be well understood Chen, et al. Expires August 24, 2016 [Page 3] Internet-Draft happy-eyeballs-mif February 2016 and considered before interface selection. Different preconditions can impact subsequent behaviors. Users concern about high- reliability or high-speed or less-cost would make different choicies. A flexible mechanism is provided to make smart decision. 4. Happiness Parameters This section provides a design proposal for HE-MIF. Two sets of "Happiness" parameters have been defined. It serves applications and initiates HE-MIF connections tests subsequently. Going through the process, MIF nodes could pick an appropriate interface which would correspond to user demands. The two sets of "Happiness" parameters are called Hard Set and Soft Set respectively. o Hard Set: Contains parameters which must be complied with. It helps to select candidate interfaces through which a particular flow should be directed. These should be seen as constraints on the choice, such as provider policies, support for IPv4 or IPv6, and other parameters which would prevent a particular interface and transport from being used by a particular flow. Parameters in the hard set should be easy to use and understand. When several parameters in the hard set are in conflict, the user's preference should be prioritized. * User's preference: users may express preferences which likely not have a formally technical language , like "No 3G while roaming", "Only use free WiFi", etc. * Operator policy: operators may deliver the customized policies in a particular network environment because of geo-location or services regulation considerations. One example in 3GPP network is that operator could deliver policies from access network discovery and selection function (ANDSF). o Soft Set: Contains factors which impact the selection of the path across which a particular flow should be transmitted among the available interfaces and transports which meet the hard set requirements described above. Examples might include: * PVD-ID (Provisioning Domain Identity): PVD-aware node may decide to use one preferred PVD or allow use multiple PVDs simultaneously for applications. The node behavior should be consistent with MPVD architecture [RFC7556]. * Next hop: [RFC4191] allows configuration of specific routes to a destination. Chen, et al. Expires August 24, 2016 [Page 4] Internet-Draft happy-eyeballs-mif February 2016 * DNS selection: [RFC6731] could configure nodes with information to indicate a DNS server address for a particular namespace. * Source address selection: the information provided by [RFC6724] should be considered. * Other factors: There is a common practice may impact interface selection, e.g. WiFi is preferable. Such conventional experiences should also be considered. 5. HE-MIF behavior Corresponding to the two sets of parameters, a HE-MIF node may take a two-steps approach. One is to do "Hard" decision to synthesize policies from different actors (e.g., users and network operator). In a nutshell, that is a filter which will exclude the interfaces from any further consideration. The second is to adjust how a node make a connection on multiple interfaces after the filter. It's sorting behavior. In the multiple provisioning domain architecture, a PVD aware node takes connectivity tests as described in Section 5.3 of [RFC7556]. A PVD agnostic node take other parameters in the Soft Set to proceed the sort process. Those two steps are described as following sub-sections. It should be noted that HE-MIF doesn't prescribe such two-step model. It will be very specific to particular cases and implementations. For example, if only one interface is left after the first step, the process is likely ceased. 5.1. First Step, Filter One goal of the filter is to reconcile multiple selection policies from users or operators. Afterwards, merged demands would be mapped to a set of candidate interfaces, which is judged as qualified. Decision on reconciliation of different policies will depend very much on the deployment scenario. An implementation may not be able to determine priority for each policies without explicit configuration provided by users or administrator. For example, an implementation may by default always prefer the WiFi because of cost saving consideration. Whereas, users may dedicatedly prefer a 3GPP network interface to seek high-reliability or security benefits even to manually turn off WiFi interface. The decision on mergence of policies may be made by implementations, by node administrators, even by other standards investigating customer behavior. However, it's worth to note that a demand from users should be normally considered higher priority than from other actors. Chen, et al. Expires August 24, 2016 [Page 5] Internet-Draft happy-eyeballs-mif February 2016 The merged policies would serve as a filter principle doing iterate across the list of all known interfaces. Qualified interface would be selected to Sort processing at the next step. 5.2. Second Step, Sort A Sort process guarantees a fast interface selection with fallback capacities. As stated in [RFC7556], a PVD-aware node shall perform connectivity test and, only after validation of the PVD, consider using it to serve application connections requests. In current implementations, some nodes already implement this, e.g., by trying to reach a dedicated web server (see [RFC6419] ). If anything is abnormal, it assumes there is a proxy on the path. This status detection is recommended to be used in HE-MIF to detect DNS interception or HTTP proxy that forces a login or a click-through. Unexamined PVDs or interfaces should be accounted as "unconnected". It should not join the sort process. Afterwards, two phases normally are involved in a Sort process, i.e., name resolving and connection establishment. The Soft set parameters defined in Section 4 should considered at this stage. When a node initiates name resolution requests, it should check if there is a matched PVD ID for the destination name. A PVD agnostic node may request DNS server selection DHCP option [RFC6731] for interface selection guidance. Those information may weight a particular interface to be preferred to others sending resolving requests. If the node can't find useful information in the Soft Set, DNS queries would be sent out on multiple interfaces in parallel to maximize chances for connectivity. Some additional discussions of DNS selection consideration of HE-MIF are described in Section 7.3. Once a destination address was resolved, a connection is to be setup. For the given destination address, a PVD-aware node selects a next- hop and source address associated with that PVD in the name resolution process. A PVD agnostic node may receive certain next hop in a RA message [RFC4191], the node selects best source address according to the rules [RFC6724]. When destination and source pairs are identified, it should be treated with higher priority compared to others and choose to initiate the connection in advance. This could avoid thrashing the network, by not making simultaneous connection attempts on multiple interfaces. After making a connection attempt on the preferred pairs and failing to establish a connection within a certain time period (see Section 7.2), a HE-MIF implementation will decide to initiate connection attempt using rest of interfaces in parallel. This fallback consideration will make subsequent connection attempts successful on non-preferable interfaces. Chen, et al. Expires August 24, 2016 [Page 6] Internet-Draft happy-eyeballs-mif February 2016 The node would cache information regarding the outcome of each connection attempt. Cache entries would be flushed periodically. A system-defined timeout may take place to age the state. Maximum on the order of 10 minutes defined in [RFC6555] is recommended to keep the interface state changes synchronizing with IP family states. If there are no specific Soft Set provided, all selected interfaces should be equally treated. The connections would initiate on several interface simultaneously. The goal here is to provide the most fast connection for users, by quickly attempting to connect using each candidate interface. Afterwards, the node would do the same caching and flushing process as described above. 6. Implementation Framework The simplest way for the implementation is within the application itself. The mechanism described in the document would not require any specific support from the operating system beyond the commonly available APIs that provide transport service. It could also be implemented as high-level API approach, linking to MIF-API [I-D.ietf-mif-api-extension]. 7. Additional Considerations 7.1. Usage Scope Connection-oriented transports (e.g., TCP, SCTP) are directly applied as scoped in [RFC6555]. For connectionless transport protocols (e.g., UDP), a similar mechanism can be used if the application has request/response semantics. Further investigrations are out of the document scope. 7.2. Fallback Timeout When the preferred interface was failed, HE-MIF would trigger a fallback process to start connection initiation on several candidate interfaces. It should set a reasonable wait time to comfort user experience. Aggressive timeouts may achieve quick interface handover, but at the cost of traffic that may be chargeable on certain networks, e.g. the handover from WiFi to 3GPP networks brings a charge to customers. Considering the reasons, it is recommended to prioritize the input from users (e.g., real customers or applications) through user interface. For default-setting on a system, a hard error [RFC1122] in replied ICMP could serve as a trigger for the fallback process. When the ICMP soft error is present or non-response was received, it's recommended that the timeout should be large enough to allow connection retransmission. [RFC1122] states that such timer must be at least 3 minutes to Chen, et al. Expires August 24, 2016 [Page 7] Internet-Draft happy-eyeballs-mif February 2016 provide TCP retransmission. However, several minutes delay may not inappropriate for user experiences. A widespread practice [RFC5461] sets 75 seconds to optimize connection process. More optimal timer may be expected. The particular setting will be very specific to implementations and cases. The memo didn't try to provide a concrete value because of following concerns. o RTT (Round-Trip Time) on different interfaces may vary quite a lot. A particular value of timeout may not accurately help to make a decision that this interface doesn't work at all. On the contrary, it may cause a misjudgment on a interface, which is not very fast. In order to compensate the issues, the timeout setting based on past experiences of a particular interface may help to make a fair decision. Whereas, it's going beyond the capability of Happy Eyeballs [RFC6555]. Therefore, it leaves a particular implementation. o In some cases, fast interface may not be treated as "best". For example, a interface could be evaluated in the principle of bandwidth-delay, termed "Bandwidth-Delay-Product ". Happy Eyeballs measures only connection speed. That is, how quickly a TCP connection is established . It does not measure bandwidth. If the fallback has to take various factors into account and make balanced decision, it's better to resort to a specific context and implementation. 7.3. DNS Selections In the Sort process, HE-MIF prioritizes PVD-ID match or [RFC6731] inputs to select a proper server. It could help to address following two cases. o A DNS answer may be only valid on a specific provisioning domain, but DNS resolver may not be aware of that because DNS reply is not kept with the provisioning from which the answer comes. The situation may become worse if asking internal name with public address response or asking public name with private address answers. o Some FQDNs can be resolvable only by sending queries to the right server (e.g., intranet services). Otherwise, a response with NXDOMAIN is replied. Fast response is treated as optimal only if the record is valid. That may cause messy for data connections, since NXDOMAIN doesn't provide useful information. By doing HE-MIF, it can help to solve the issues of DNS interception with captive portal. The DNS server modified and replied the answer Chen, et al. Expires August 24, 2016 [Page 8] Internet-Draft happy-eyeballs-mif February 2016 with the IP address of captive portal rather than the intended destination address. In those cases, TCP connection may succeed, but Internet connectivity is not available. It results in lack of service unless user has authenticated. HE-MIF recommended using network connectivity status probes to examine a pre-configured URL for detecting DNS interception on the path (see more in Section 5.2). The node will be able to automatically rely upon other interfaces to select right DNS servers by excluding the unexamined interfaces. 7.4. Flow Continuity [I-D.deng-mif-api-session-continuity-guide] describes session continuity guidance for application developers. The flow continuity topic is beyond this document scope. 8. IANA Considerations This memo includes no request to IANA. 9. Security Considerations The security consideration is following the statement in [RFC6555] and [RFC6418]. 10. Acknowledgements The authors would like to thank Margaret Wasserman, Hui Deng, Erik Kline, Stuart Cheshire, Teemu Savolainen, Jonne Soininen, Simon Perreault, Zhen Cao, Dmitry Anipko, Ted Lemon, Daniel Migault, Russ White and Bing Liu for their helpful comments. 11. References 11.1. Normative References [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - Communication Layers", STD 3, RFC 1122, DOI 10.17487/RFC1122, October 1989, . [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, November 2005, . [RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with Dual-Stack Hosts", RFC 6555, DOI 10.17487/RFC6555, April 2012, . Chen, et al. Expires August 24, 2016 [Page 9] Internet-Draft happy-eyeballs-mif February 2016 [RFC6724] Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown, "Default Address Selection for Internet Protocol Version 6 (IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012, . [RFC6731] Savolainen, T., Kato, J., and T. Lemon, "Improved Recursive DNS Server Selection for Multi-Interfaced Nodes", RFC 6731, DOI 10.17487/RFC6731, December 2012, . 11.2. Informative References [I-D.deng-mif-api-session-continuity-guide] Deng, H., Krishnan, S., Lemon, T., and M. Wasserman, "Guide for application developers on session continuity by using MIF API", draft-deng-mif-api-session-continuity- guide-04 (work in progress), July 2014. [I-D.ietf-mif-api-extension] Liu, D., Lemon, T., Ismailov, Y., and Z. Cao, "MIF API consideration", draft-ietf-mif-api-extension-05 (work in progress), February 2014. [RFC5461] Gont, F., "TCP's Reaction to Soft Errors", RFC 5461, DOI 10.17487/RFC5461, February 2009, . [RFC6418] Blanchet, M. and P. Seite, "Multiple Interfaces and Provisioning Domains Problem Statement", RFC 6418, DOI 10.17487/RFC6418, November 2011, . [RFC6419] Wasserman, M. and P. Seite, "Current Practices for Multiple-Interface Hosts", RFC 6419, DOI 10.17487/RFC6419, November 2011, . [RFC7556] Anipko, D., Ed., "Multiple Provisioning Domain Architecture", RFC 7556, DOI 10.17487/RFC7556, June 2015, . Authors' Addresses Chen, et al. Expires August 24, 2016 [Page 10] Internet-Draft happy-eyeballs-mif February 2016 Gang Chen China Mobile 29, Jinrong Avenue Xicheng District, Beijing 100033 China Email: phdgang@gmail.com, chengang@chinamobile.com Carl Williams Consultant El Camino Real Palo Alto, CA 94306 USA Email: carlw@mcsr-labs.org Dan Wing Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134 USA Email: dwing@cisco.com Andrew Yourtchenko Cisco Systems, Inc. De Kleetlaan, 7 Diegem B-1831 Belgium Email: ayourtch@cisco.com Chen, et al. Expires August 24, 2016 [Page 11]