Happy Eyeballs Extension for Multiple Interfaces
draft-ietf-mif-happy-eyeballs-extension-07

Internet Engineering Task Force                                  G. Chen
Internet-Draft                                              China Mobile
Intended status: Informational                               C. Williams
Expires: April 19, 2016                                       Consultant
                                                                 D. Wing
                                                          A. Yourtchenko
                                                     Cisco Systems, Inc.
                                                        October 17, 2015

            Happy Eyeballs Extension for Multiple Interfaces
               draft-ietf-mif-happy-eyeballs-extension-07

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 interfaces according to defined policy.  This would
   choose the fastest interface with an automatic fallback.

Status of This Memo

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   carefully, as they describe your rights and restrictions with respect
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Happiness Parameters  . . . . . . . . . . . . . . . . . . . .   3
   4.  HE Behavior in MIF  . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  First Step, Filter  . . . . . . . . . . . . . . . . . . .   5
     4.2.  Second Step, Sort . . . . . . . . . . . . . . . . . . . .   5
   5.  Implementation Framework  . . . . . . . . . . . . . . . . . .   7
   6.  Additional Considerations . . . . . . . . . . . . . . . . . .   7
     6.1.  Usage Scope . . . . . . . . . . . . . . . . . . . . . . .   7
     6.2.  Fallback Timeout  . . . . . . . . . . . . . . . . . . . .   7
     6.3.  DNS Selections  . . . . . . . . . . . . . . . . . . . . .   8
     6.4.  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

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 fast path
   to connect a server.  That is a good method to achieve smart path
   selection.  However, the assumption is a single-homed context.  The
   interaction with multiple interfaces is deferred for further study.

   [RFC7556] has proposed a multiple provisioning domain architecture.
   This memo has been proposed to extend happy eyeballs algorithm to fit
   into the multiple interfaces architecture.  Several additional
   considerations have been elaborated to analyze the user demands and
   initiate HE-MIF connections.  It allows a node with multiple
   interfaces picking a fast flow path.

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2.  Use Cases

   The section describes use cases in existing networks.

   Use Case: WiFi is broken

   A MIF node has both 3/4G and WiFi interface.  When the node enters a
   WiFi area, a common practice would always prefer WiFi because it'
   cheap and fast-speed normally.  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 may be an authentication required coming into play, or unstable
   Layer 2 conditions.  In order to figure out the problems, users have
   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 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.

   Use Case: Policy Conflict

   A node has WiFi and 3/4G access simultaneously.  In 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 policy confliction.  The transition to IPv6 is
   likely to encourage IPv6 and prefer IPv6[RFC6724].  If the 3/4G path
   has IPv6 on it and the WiFi does not, a suboptimal interface might be
   chosen from the cost saving perspective.  With HE-MIF, 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

   This section provides 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 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: It contains parameters which have mandatory indications
      that interface behavior should comply with.  This might provide an

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      interface for applications constraints or delivering operator's
      policies.  Basically, parameters in Hard set should be easy-to-use
      and easy-to-understand.  The users would directly use those.  When
      several hard parameters were conflicted, user's preference should
      be prioritized.

      *  User's preference: users would express preferences which may
         not have a formally technical language , like "No 3G while
         roaming", "Only use free WiFi", etc.

      *  Operator policy: 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).

   o  Soft Set: It contains factors involving in the selection of the
      fastest path.  The following is considered as for the
      justification.

      *  PVD-ID (Provisioning Domain Identity): PVD-aware node may
         decide to use one preferred PVD or allow use mulitple PVDs
         simultanenously for applications.  The node behavior should be
         consistent with MPVD architecture.

      *  Next hop: [RFC4191] allows configuration of specific routes to
         a destination.

      *  DNS selection: [RFC6731] could configure nodes with information
         to indicate DNS server address for a particular namespace.

      *  Source address selection: the information provided by [RFC6724]
         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 Behavior in MIF

   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 we 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

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   [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 one interface on a particular PVD is left after the first
   step, the process would be ceased.

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 3/4G
   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.

   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.

4.2.  Second Step, Sort

   Sort process guarantees 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.  A common
   practise is to probe a pre-configured URL to check network
   connectivity status as soon as a node access a network at bootstrap
   or changes to different networks, e.g.  Windows Vista, Windows 7,
   Windows Server 2008 and iOS.  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.

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   Afterwards, two phases normally are involved in a sort process, i.e.
   name resolving and connection establishment.  Parameters in a soft
   set 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 one prior 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 on
   relevant PVDs in parallel to maximize chances for connectivity.  Some
   additional discussions of DNS selection consideration of HE-MIF are
   described in Section 6.3.

   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 RA message[RFC4191] , the node selects best source address
   according to the[RFC6724] rules.  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 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 interfaces.

   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 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.

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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), 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
   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 3/4G 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 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 provide TCP
   retransmission.  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 due to 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

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      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.

6.3.  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
   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 4.2).
   The node will be able to automatically rely upon other interfaces to
   select right DNS servers by excluding the unexamined interfaces.

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6.4.  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, Teemu Savolainen, Jonne Soininen, Simon
   Perreault, Zhen Cao, Dmitry Anipko and Ted Lemon for their helpful
   comments.

10.  References

10.1.  Normative References

   [RFC1122]  Braden, R., Ed., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122,
              DOI 10.17487/RFC1122, October 1989,
              <http://www.rfc-editor.org/info/rfc1122>.

   [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and
              More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191,
              November 2005, <http://www.rfc-editor.org/info/rfc4191>.

   [RFC6555]  Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with
              Dual-Stack Hosts", RFC 6555, DOI 10.17487/RFC6555, April
              2012, <http://www.rfc-editor.org/info/rfc6555>.

   [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,
              <http://www.rfc-editor.org/info/rfc6724>.

   [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,
              <http://www.rfc-editor.org/info/rfc6731>.

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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-05 (work in
              progress), February 2014.

   [RFC5461]  Gont, F., "TCP's Reaction to Soft Errors", RFC 5461,
              DOI 10.17487/RFC5461, February 2009,
              <http://www.rfc-editor.org/info/rfc5461>.

   [RFC6157]  Camarillo, G., El Malki, K., and V. Gurbani, "IPv6
              Transition in the Session Initiation Protocol (SIP)",
              RFC 6157, DOI 10.17487/RFC6157, April 2011,
              <http://www.rfc-editor.org/info/rfc6157>.

   [RFC6418]  Blanchet, M. and P. Seite, "Multiple Interfaces and
              Provisioning Domains Problem Statement", RFC 6418,
              DOI 10.17487/RFC6418, November 2011,
              <http://www.rfc-editor.org/info/rfc6418>.

   [RFC7556]  Anipko, D., Ed., "Multiple Provisioning Domain
              Architecture", RFC 7556, DOI 10.17487/RFC7556, June 2015,
              <http://www.rfc-editor.org/info/rfc7556>.

Authors' Addresses

   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

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   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

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