Internet Engineering Task Force G. Chen Internet-Draft China Mobile Intended status: Informational C. Williams Expires: January 10, 2013 Consultant D. Wing A. Yourtchenko Cisco Systems, Inc. July 9, 2012 Happy Eyeballs Extension for Multiple Interfaces draft-ietf-mif-happy-eyeballs-extension-00 Abstract Currently the interface selection in multi-interface environment is exclusive - only one interface can be used at the time, frequently needing manual intervention. Happy Eyeballs in MIF would make the selection process smoother by using the connectivity checks over a pre-filtered according to defined policy set of interfaces. This would choose "best" interface with an automatic fallback. 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 January 10, 2013. Copyright Notice Copyright (c) 2012 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 January 10, 2013 [Page 1] Internet-Draft happy-eyeballs-mif July 2012 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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 3. Happiness Parameters . . . . . . . . . . . . . . . . . . . . . 5 4. HE Behaviour in MIF . . . . . . . . . . . . . . . . . . . . . 6 4.1. First Step, Filter . . . . . . . . . . . . . . . . . . . . 6 4.2. Second Step, Sort . . . . . . . . . . . . . . . . . . . . 7 5. Implementation Framework . . . . . . . . . . . . . . . . . . . 8 6. Additional Considerations . . . . . . . . . . . . . . . . . . 8 6.1. Usage Scope . . . . . . . . . . . . . . . . . . . . . . . 8 6.2. Fallback Timeout . . . . . . . . . . . . . . . . . . . . . 8 6.3. Flow Continuity . . . . . . . . . . . . . . . . . . . . . 9 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 8. Security Considerations . . . . . . . . . . . . . . . . . . . 9 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 10.1. Normative References . . . . . . . . . . . . . . . . . . . 9 10.2. Informative References . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 Chen, et al. Expires January 10, 2013 [Page 2] Internet-Draft happy-eyeballs-mif July 2012 1. Introduction In multiple interface context, the problems raised by hosts with multiple interfaces have been discussed. The MIF problem statement[RFC6418] described the various issues when using a wrong domain selection on a MIF node. Happy Eyeballs (HE) [RFC6555] described how a dual-stack client can determine the functioning path to a dual-stack server. It's using stateful algorithm to help applications quickly determine if IPv6 or IPv4 is the most optimal path to connect a server. That is a good method to achieve smart path selection. However, the assumption there is a single-homed context. The interaction with multiple interfaces is deferred for further study. This memo has been proposed to extend happy eyeballs algorithm to fit into multiple interfaces context. Several additional considerations have been elaborated to analyze the user demands and initiate HE-MIF connections. This document describes a two-stage algorithm, which should allow a node with multiple interfaces both pick a satisfactory flow path, and identify the appropriate IP address family. 2. Problem Statement The section enumerates several concrete use cases in existing networks. Case 1: WiFi is broken o [Scenario] A MIF node has both 3G and WIFI interface. When the node enters a WiFi area, a common practice would always prefer WiFi because it' cheap and fast-speed normally. o [Problem] User assumes the wifi is working, because the node already got IP address from WiFi. However, he can't run applications due to Internet connectivity being unavailable. This could be an authentication required coming into play, or unstable Layer 2 conditions. In order to figure out the problems, users have to go and turn off the WiFi manually. o [Workaround] Users can indicate their desire with some setting on the phone. For instance, they may prefer to wait a little bit of time but not forever. After the timer is expired, users would finally give up the WiFi path and try to establish connection over 3G path. Users may won't want the wait time too short, because the 3G path for most people is more expensive than wifi path. Case 2: VPN (virtual private network) scenario Chen, et al. Expires January 10, 2013 [Page 3] Internet-Draft happy-eyeballs-mif July 2012 o [Scenario] In some cases, a node has multiple interface because of VPN. Users would only have interests to connect a corporate network inside VPN. While, connecting to Internet would work outside the VPN. o [Problem] That is normally a implementation consideration that unmanaged interface may be considered less trustworthy than managed. That results in trusted interfaces having the highest priority. This setting may steer all traffic to VPN interface. When this is a traffic heading to a corporate site, everything is fine. But sometimes, the connections out to Internet sites may suffer from long-distance path delays. o [Workaround] It's desirable if routing could be bound to each interface. However, a node following weak host model[RFC1122] takes routing tables as node-scoped. One solution is to perform parallel IP connectivity checks before selecting an interface. Case 3: 3G/LTE tethering scenario o [Scenario] Many mobile phones are equipped with software to offer tethered Internet access. It shares their Internet connection with another Internet-capable mobile phone or other devices over Wi-Fi. Apart from wifi link, there are some other links involved on the tethered phone, e.g. 3G access. o [Problem] The WiFi link that tethered phone see is not free WiFi link, i.e. it might be 3G backhaul. The policy of "always WiFi" leads to all traffic being sent over the tethering WiFi. Usually, such tethering WiFi link puts sharing limitation to access nodes. It could cause contention on both that WiFi link and the backhaul 3G link, while it be higher cost than going on the 3G that is built in the handset. o [Workaround] To solve that, it is necessary for the node to be aware of not only the link layer information, but also services information, like billable or free. That could help to facilitate the execution of the algorithm. Same concern has been documented in Section 4.4 of [RFC6418]) Case 4: Policy Conflict o [Scenario] A node has WiFi and 3G access simultaneously. In mobile network, IPv6-only may be preferable since IPv6 has the potential to be simpler than dual-stack. WiFi access still remain on IPv4. Chen, et al. Expires January 10, 2013 [Page 4] Internet-Draft happy-eyeballs-mif July 2012 o [Problem] The problem is caused by policy confliction. The transition to IPv6 is likely to encourage IPv6 and prefer IPv6[RFC3484]. If the 3G path has IPv6 on it and the WiFi does not, a suboptimal interface might be chosen from the cost saving perspective. o [Workaround] Users interests should be well understood and considered before interface selection. The different preconditions may impact subsequent behaviors. Users concern about high-reliability or high-speed or less-cost should make different choice. A flexible mechanism should be provided allow to make smart decision. 3. Happiness Parameters To solve the problems, this section provide the design proposal for HE-MIF. Two sets of "Happiness" parameters have been defined. It serves upper applications and initiates HE-MIF connections to below level API subsequently. Going through this two-stage 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: It contains parameters which have mandatory indications that interface behaviour should comply with. This might provide an interface for applications constraints or delivering operator's policies. Basically, parameters in Hard set should be easy-to-use and easy-to-understand. The potential users would directly use those. * Operator policies: operators would deliver the customized policies in particular network environments due to 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). * Application constraints: applications would express preferences which may not have a formally technical language , like "No 3G while roaming", "Only use free WiFi", etc. o Soft set: It's a factor contributing to the best path. The following is considered as for the justification. * Next hop: [RFC4191] and DHCPv6 Route Option [I-D.ietf-mif-dhcpv6-route-option] allow configuration of specific routes to a destination. Chen, et al. Expires January 10, 2013 [Page 5] Internet-Draft happy-eyeballs-mif July 2012 * DNS selection: [I-D.ietf-mif-dns-server-selection] could configure nodes with information to indicate DNS server address for a particular namespace. * Source address selection: the information provided by [RFC3484] would 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. 4. HE Behaviour in MIF Corresponding to the two sets of parameters, an HE-MIF node will take a two-step approach. One is to do "hard" decision to synthesize policies from different actors (e.g., users and network operator). In a nutshell, that is filter which will exclude the interfaces from any further consideration. The second is to adjust how we make a connection on multiple interfaces after the filter. It's a sorting behaviour. Those two things are described as following sub-sections. 4.1. First Step, Filter One goal of filter is to reconcile multiple selection policies from users or operators. Afterwards, the 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 due to cost saving consideration. Whereas, users may dedicatedly prefer 3G interface to seek high-reliability or security benefits even to actively turn off WiFi interface. The decision on mergence of policies may be made by implementation, by node administrators, even by other standards investigating customer behaviour. However, it's worth to note that a demand from users may be normally considered higher priority than from other actors. 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 next step. Chen, et al. Expires January 10, 2013 [Page 6] Internet-Draft happy-eyeballs-mif July 2012 4.2. Second Step, Sort Sort process would guarantee "best" interface selection with fallback capacities. Two phases normally are involved in a whole session, i.e. name resolving and data session establishing. Parameters in Soft set should considered at this stage. When the node initiates name requests, it should follow the instruction in [I-D.ietf-mif-dns-server-selection]if DNS server selection DHCP option is provided. Otherwise, several alternative behaviour for DNS server selection described in Appendix A of [I-D.ietf-mif-dns-server-selection]maybe performed. Once a peer address was resolved, a connection would be intended to setup. Heading to a destination, a particular interface may comply with soft parameter configuration, e.g. next hop[RFC4191] [I-D.ietf-mif-dhcpv6-route-option], source address selection[RFC3484] or common practice. A particular interface should be treated with higher priority compared to others. And, it should be choose to initiate the connection in advance. This could avoid thrashing the network, by not (always) making simultaneous connection attempts on multiple interfaces. After making a connection attempt on the preferred interface and failing to establish a connection within a certain time period (see Section 6.2), a HE-MIF implementation will decide to initiate connection attempt using rest of interfaces in parallel. This fallback consideration may make subsequent connection attempts successful on non-preferable interface. 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 filmily states. So long as new connections are being attempted by the MIF-node, such an implementation should occasionally make connection attempts using the soft-parameter's preferred interface, as it may have become functional again. If there are no specific soft-parameters provided, all interface should be equally treated. The connections would initiate on several interface simultaneously. The goal here is to provide fast connection for users, by quickly attempting to connect using one of interfaces. Afterwards, the node would do the same caching and flushing process as described above. Chen, et al. Expires January 10, 2013 [Page 7] Internet-Draft happy-eyeballs-mif July 2012 5. 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]. A number of enhancements could be added, making the use of the high-level APIs much more productive in building applications. 6. Additional Considerations 6.1. Usage Scope Connection-oriented transports (e.g., TCP, SCTP) could be directly applied as scoped in [RFC6555]. For connectionless transport protocols (e.g., UDP), it was also described "a similar mechanism can be used if the application has request/ response semantics (e.g., as done by Interactive Connectivity Establishment (ICE) to select a working IPv6 or IPv4 media path[RFC6157])." 6.2. Fallback Timeout When the preferred interface was failed, HE-MIF would trigger fallback process to start connection initiation on several candidate interfaces. It should set a reasonable wait time to comfort user experiences. 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 3G would bring a bill to customers. Considering the reasons, it is recommended to prioritize the input from users(e.g. real customers or applications) through UI. 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 provide TCP retransmission. Several minutes delay may not inappropriate for user experiences. A widespread practice[RFC5461] sets 75 seconds to optimize connection process. [Editor note:It should be noted that 75 seconds is a worse case if host can't get UI input or hard error in ICMP. More optimal timer may need to be defined depending on further investigation.] Chen, et al. Expires January 10, 2013 [Page 8] Internet-Draft happy-eyeballs-mif July 2012 6.3. Flow Continuity Interface changing should only happen at the beginning of new session in order to keep flow continuity for ongoing TCP session. Dynamic movement of traffic flows are beyond the scope of this document. 7. IANA Considerations This memo includes no request to IANA. 8. Security Considerations The security consideration is following the statement in [RFC6555]and [RFC6418]. 9. Acknowledgements The authors would like to thank Margaret Wasserman, Hui Deng, Erik Kline, Stuart Cheshire and Teemu Savolainen for their helpful comments. 10. References 10.1. Normative References [I-D.ietf-mif-dns-server-selection] Savolainen, T., Kato, J., and T. Lemon, "Improved Recursive DNS Server Selection for Multi-Interfaced Nodes", draft-ietf-mif-dns-server-selection-10 (work in progress), June 2012. [RFC1122] Braden, R., "Requirements for Internet Hosts - Communication Layers", STD 3, RFC 1122, October 1989. [RFC3484] Draves, R., "Default Address Selection for Internet Protocol version 6 (IPv6)", RFC 3484, February 2003. [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and More-Specific Routes", RFC 4191, November 2005. [RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with Dual-Stack Hosts", RFC 6555, April 2012. Chen, et al. Expires January 10, 2013 [Page 9] Internet-Draft happy-eyeballs-mif July 2012 10.2. Informative References [I-D.ietf-mif-api-extension] Liu, D., Lemon, T., Ismailov, Y., and Z. Cao, "MIF API consideration", draft-ietf-mif-api-extension-00 (work in progress), March 2012. [I-D.ietf-mif-dhcpv6-route-option] Dec, W., Mrugalski, T., Sun, T., and B. Sarikaya, "DHCPv6 Route Options", draft-ietf-mif-dhcpv6-route-option-04 (work in progress), February 2012. [I-D.ietf-mif-problem-statement] Blanchet, M. and P. Seite, "Multiple Interfaces and Provisioning Domains Problem Statement", draft-ietf-mif-problem-statement-15 (work in progress), May 2011. [RFC5461] Gont, F., "TCP's Reaction to Soft Errors", RFC 5461, February 2009. [RFC6157] Camarillo, G., El Malki, K., and V. Gurbani, "IPv6 Transition in the Session Initiation Protocol (SIP)", RFC 6157, April 2011. [RFC6418] Blanchet, M. and P. Seite, "Multiple Interfaces and Provisioning Domains Problem Statement", RFC 6418, November 2011. Authors' Addresses Gang Chen China Mobile 53A,Xibianmennei Ave., Xuanwu District, Beijing 100053 China Email: phdgang@gmail.com Chen, et al. Expires January 10, 2013 [Page 10] Internet-Draft happy-eyeballs-mif July 2012 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 January 10, 2013 [Page 11]