Internet DRAFT - draft-liu-mif-api-extension

draft-liu-mif-api-extension






Network Working Group                                             D. Liu
Internet-Draft                                              China Mobile
Intended status: Informational                                Ted. Lemon
Expires: May 3, 2012                                             Nominum
                                                          Yuri. Ismailov
                                                                Ericsson
                                                                  Z. Cao
                                                            China Mobile
                                                        October 31, 2011


                         MIF API consideration
                     draft-liu-mif-api-extension-06

Abstract

   This document describes an abstract API that provides the minimal
   functionality required for a program to communicate effectively with
   peers and services on the network while running on a host that has
   more than one active network interface.  This API is abstract: we
   describe the functionality that must be provided, not the bindings
   that should be used to provide that functionality.  The functionality
   described here provides the building blocks from which higher-level
   APIs might be built, and is not intended to be used directly by
   typical applications.

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 May 3, 2012.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




Liu, et al.                Expires May 3, 2012                  [Page 1]

Internet-Draft              MIF API Extension               October 2011


   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
   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 . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Conventions used in this document  . . . . . . . . . . . . . .  4
   3.  MIF API Concept  . . . . . . . . . . . . . . . . . . . . . . .  5
     3.1.  Provisioning Domains . . . . . . . . . . . . . . . . . . .  5
     3.2.  Provisioning Domain Agnosticism  . . . . . . . . . . . . .  5
     3.3.  MIF API Elements . . . . . . . . . . . . . . . . . . . . .  6
       3.3.1.  Application Element  . . . . . . . . . . . . . . . . .  6
       3.3.2.  High Level API . . . . . . . . . . . . . . . . . . . .  7
       3.3.3.  MIF API  . . . . . . . . . . . . . . . . . . . . . . .  7
       3.3.4.  Communications API . . . . . . . . . . . . . . . . . .  7
       3.3.5.  Network Link API . . . . . . . . . . . . . . . . . . .  7
     3.4.  MIF API communication model  . . . . . . . . . . . . . . .  8
       3.4.1.  POST MESSAGE call  . . . . . . . . . . . . . . . . . .  8
       3.4.2.  CHECK MESSAGE call . . . . . . . . . . . . . . . . . .  8
       3.4.3.  GET MESSAGE call . . . . . . . . . . . . . . . . . . .  8
     3.5.  MIF Messages . . . . . . . . . . . . . . . . . . . . . . .  8
       3.5.1.  Announce Interfaces  . . . . . . . . . . . . . . . . .  9
       3.5.2.  Stop Announcing Interfaces . . . . . . . . . . . . . .  9
       3.5.3.  Interface Announcement . . . . . . . . . . . . . . . .  9
       3.5.4.  No Interface Announcement  . . . . . . . . . . . . . .  9
       3.5.5.  Announce Provisioning Domain . . . . . . . . . . . . .  9
       3.5.6.  Stop Announcing Provisioning Domains . . . . . . . . . 10
       3.5.7.  Provisioning Domain Announcement . . . . . . . . . . . 10
       3.5.8.  No Provisioning Domain Announcement  . . . . . . . . . 10
       3.5.9.  Announce Configuration Element . . . . . . . . . . . . 10
       3.5.10. Configuration Element Announcement . . . . . . . . . . 11
       3.5.11. No Configuration Element Announcement  . . . . . . . . 11
       3.5.12. Announce Address . . . . . . . . . . . . . . . . . . . 11
       3.5.13. Address Announcement . . . . . . . . . . . . . . . . . 12
       3.5.14. No Address Announcement  . . . . . . . . . . . . . . . 12
       3.5.15. Get Configuration Data . . . . . . . . . . . . . . . . 12
       3.5.16. Translate Name . . . . . . . . . . . . . . . . . . . . 12
       3.5.17. Stop Translating Name  . . . . . . . . . . . . . . . . 13
       3.5.18. Name Translation . . . . . . . . . . . . . . . . . . . 13
       3.5.19. Connect to Address . . . . . . . . . . . . . . . . . . 13



Liu, et al.                Expires May 3, 2012                  [Page 2]

Internet-Draft              MIF API Extension               October 2011


       3.5.20. Connect to Address From Address  . . . . . . . . . . . 13
       3.5.21. Connected  . . . . . . . . . . . . . . . . . . . . . . 14
       3.5.22. Not Connected  . . . . . . . . . . . . . . . . . . . . 14
   4.  Example Usage  . . . . . . . . . . . . . . . . . . . . . . . . 14
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 16
   7.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 16
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 16
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 16
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17








































Liu, et al.                Expires May 3, 2012                  [Page 3]

Internet-Draft              MIF API Extension               October 2011


1.  Introduction

   Traditionally, hosts that communicate on the network have done so
   over a single network link, which is provided by a single service
   provider.  This simple environment is relatively easy to program to,
   and relatively predictable.

   However, this relatively simple case is no longer the norm.  A
   typical modern host may have one or two wireless interfaces: a
   wireless interface connected to a broadband network, and possibly
   another connected to some kind of cellular network.  The same host
   may also have a wired interface which is sometimes connected to
   another broadband link.  It is also quite common for hosts to have
   VPN links that are configured, for example, for access to corporate
   networks, or for access to network privacy services.

   As a result, it is now quite typical that a program attempting to
   communicate in such an environment will be presented with conflicting
   configuration information from more than one provider.  In addition,
   the cost of bandwidth on different links and the power required ny
   those links may require consideration.

   The API specified in this document is intended to describe the
   minimal complete set of API calls required to implement higher level
   APIs that solve these problems.  It is not expected that applications
   will be implemented to this API, although it should be possible to do
   so.  Rather, we expect this API to be used as a basis for building
   higher-level APIs that provide domain-specific solutions to these
   problems.  The reason for specifying a lower-level API is to enable
   any arbitrary domain- specific API to be implemented, since no single
   higher-level API is likely to satisfy the needs of every application.

   The API specified here is an abstract API.  This means that we
   specify the functionality that is required to implement the API, but
   we do not provide specific bindings for any programming language:
   these are left up to the implementation.  The API is described in
   terms of messages sent and messages received, rather than in terms of
   procedure calls, because it is necessary to be able to interleave
   these messages; a procedure call API necessarily precludes
   interleaving.


2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL","SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].




Liu, et al.                Expires May 3, 2012                  [Page 4]

Internet-Draft              MIF API Extension               October 2011


3.  MIF API Concept

   The MIF API is intended to deal with situations where more than one
   interface may be active at a time.  It must also deal with situations
   where a single interface is connected to a link that provides more
   than one type of network service.  The most common example of this
   that we expect is a dual-stack network configuration.

3.1.  Provisioning Domains

   To properly handle these multiple-service interfaces, we specify the
   API not in terms of interfaces, but in terms of provisioning domains.
   So in the case of a dual-stack network attached to a single network
   interface, there would be two provisioning domains.  If the host has
   a second interface that is connected to a link that only supports
   IPv6 service, then that host would be connected to a total of two
   network links, but three provisioning domains.

   From the perspective of the MIF API, a provisioning domain consists
   of a link, plus all the configuration information received on that
   link for that provisioning domain.  So for an IPv4 provisioning
   domain, that would be whatever information is received from the DHCP
   server.  For an IPv6 provisioning domain, the information received
   through router advertisements would be combined with the information
   recieved via DHCPv6.

   **point of discussion: it's actually possible to have two separate
   provisioning domains for IPv6 on the same wire.  Is this a case that
   could happen in practice, and that we ought to support?  I know that
   some asian countries have arrangements where the operator of the
   physical network is distinct from one or more operators who provide
   transit; I think this is all handled transparently to the host, but I
   don't really know the details.

   **point of discussion: is IPv4 stateless/Bonjour a separate
   provisioning domain?  What about IPv6 ULA?

3.2.  Provisioning Domain Agnosticism

   Although it is possible that a high-level API built on top of this
   API may be able to distinguish between provisioning domains, at the
   level of this API, no such distinction can be made.  Each
   provisioning domain is treated separately, and it is the
   responsibility of the higher-level API or of the application to
   decide which provisioning domain or domains to actually use.






Liu, et al.                Expires May 3, 2012                  [Page 5]

Internet-Draft              MIF API Extension               October 2011


3.3.  MIF API Elements

   There are a number of different, essentially independent, pieces of
   software that need to be connected together in order to fully support
   a successful MIF communication strategy.  These elements are shown in
   figure 3.1.


               +-------------------------------------------+
               |               Application                 |
               +-------------------------------------------+
                      /\   ||          /\  ||    /\  ||
                      ||   \/          ||  ||    ||  ||
               +--------------------+  ||  ||    ||  ||
               | High Level API     |  ||  ||    ||  ||
               +--------------------+  ||  ||    ||  ||
                      /\   ||          ||  ||    ||  ||
                      ||   \/          ||  \/    ||  ||
               +------------------------------+  ||  ||
               |           MIF API            |  ||  ||
               +------------------------------+  ||  ||
                  /\  ||                         ||  \/
                  ||  ||   +-------------------------------+
                  ||  ||   +      Communications API       +
                  ||  ||   +-------------------------------+
                  ||  ||                 /\  ||
                  ||  \/                 ||  \/
               +-------------------------------------------+
               |            Network Link API               |
               +-------------------------------------------+
                       /\  ||                 /\  ||
                       ||  \/                 ||  \/
               +-------------------+  +--------------------+
               | Network Interface |  | Network Interface  |
               |         1         |  |          2         |
               +-------------------+  +--------------------+

                                 Figure 1

3.3.1.  Application Element

   This is an actual application.  Applications fall into a variety of
   broad categories, including network servers, web browsers, peer-to-
   peer programs, and so on.  Although we are focusing here on the
   mechanisms required to allow these applications to originate
   connections to remote nodes, it is worth noting that applications
   must also be able to receive connections from remote nodes.




Liu, et al.                Expires May 3, 2012                  [Page 6]

Internet-Draft              MIF API Extension               October 2011


3.3.2.  High Level API

   Applications are generally expected to originate connections using
   some general-purpose high-level API suited to their particular
   function.  It is likely that different applications may use different
   high-level APIs to communicate, depending on their particular needs.
   We do not describe the functioning of such high-level APIs; however,
   one such API under current consideration is the Happy Eyeballs for
   MIF [reference].  These APIs are expected to be able to be
   implemented using functionality like that described in the MIF API.

3.3.3.  MIF API

   This is the API being described in this document.  Generally
   speaking, this API is used by higher-level APIs.  However, it is
   permissible for applications to use the MIF API when it is deemed
   necessary.  Currently, several modern web browsers take this approach
   to establishing network connections, rather than relying on vendor-
   provided connection mechanisms.

3.3.4.  Communications API

   Once an application has originated a connection with a remote node
   using either a high-level API or the MIF API, it must communicate.
   Similarly, when an application receives a connection from a remote
   node, it must communicate with that remote node.  The communications
   API is used for this communication.  Popular examples of such APIs
   include the POSIX socket API and a variety of other related APIs.

   It is likely that in some instances, implementations of the MIF API
   will be done as extensions to the Communications API provided by a
   particular operating system; the functional separation we show here
   is intended to allow us to illustrate only those features required in
   a MIF environment, while relying on existing communications APIs to
   provide the rest.

3.3.5.  Network Link API

   This is the software that is responsible for actually managing
   whatever network links are present on a node, whether these are
   physical links or tunnels.  What precisely this functional box
   contains may vary greatly from device to device.  On a typical modern
   computer workstation, this functionality would almost certainly
   reside entirely in the system kernel; however, on an embedded device
   everything from the Application down to the Network Link API could
   easily be running together on the bare metal as a single program.

   The Network Link API can completely concealed from the Application,



Liu, et al.                Expires May 3, 2012                  [Page 7]

Internet-Draft              MIF API Extension               October 2011


   so we don't show a connection between them on the functional diagram,
   and indeed we do not talk about the functionality provided by this
   API.  The reason for showing it on the functional diagram is simply
   to show that there likely is an API in common between MIF and the
   Communications API.

3.4.  MIF API communication model

   MIF API requests are made in the form of messages posted to the MIF
   API, and messages received from it.  To accomplish this, several API
   calls are available.  These calls mediate communication between the
   MIF API and the High Level API, or between the MIF API and the
   Application.  In addition, the CHECK MESSAGE call allows the
   application to probe for or wait for messages from any of the APIs.

3.4.1.  POST MESSAGE call

   This call causes a message to be posted to the MIF API.  The call
   posts the message, and then returns.

3.4.2.  CHECK MESSAGE call

   This call checks to see if there is a message waiting either from the
   High Level API, the MIF API, or the Communications API.  Ideally it
   should be able to report the availability of any message or event
   that the application might anticipate receiving, so that the
   application can simply block waiting for such an event using this
   call.  The application should be able to do a non-blocking probe,
   wait for some limited period of time, or wait indefinitely.

   An example of a function of this type in existing practice is the
   POSIX poll() system call.

3.4.3.  GET MESSAGE call

   This call checks to see if there is a message waiting.  If there is
   no message, it returns a status code indicating that there is no
   message waiting.  If there is a message, it returns the message.

3.5.  MIF Messages

   MIF messages always go in one direction or the other: from the
   subscriber to the MIF API, or to the subscriber from the MIF API.  We
   use the term "subscriber" here to mean either the Application or the
   High Level API, since either is permitted to communicate with the MIF
   API.

   Messages described here are grouped according to function.



Liu, et al.                Expires May 3, 2012                  [Page 8]

Internet-Draft              MIF API Extension               October 2011


3.5.1.  Announce Interfaces

   This message is sent to the MIF API to ask it to send a message
   announcing the existence of any interface.  When the MIF API receives
   this message from a subscriber, it iterates across the list of all
   known interfaces; for each known interface, it sends an Interface
   Announcement message to the subscriber.

   In addition, the MIF API sets a flag indicating that the subscriber
   is interested in learning about new interfaces.  When the MIF API
   detects the presence of a new interface, it sends an Interface
   Announcement message for that interface to the subscriber.  This
   would happen, for instance, when a new tunnel is configured, or when
   a USB device that is a network interface is discovered by the Network
   API.

   Also, if a network interface goes away, either because the physical
   network device is disconnected, or because a tunnel is disabled, the
   MIF API will send a No Interface Announcement message to the
   subscriber.

3.5.2.  Stop Announcing Interfaces

   This message is sent to the MIF API when a subscriber is no longer
   interested in receiving announcements about new interfaces.
   Subsequently, the MIF API will no longer send Interface Announcement
   or No Interface Announcement messages to the subscriber.

3.5.3.  Interface Announcement

   This message announces the existence of an interface.  The
   announcement includes an interface display name and interface
   identifier.

3.5.4.  No Interface Announcement

   This message announces that an interface that had been previously
   announced is no longer present.  The announcement includes the
   interface identifier.

3.5.5.  Announce Provisioning Domain

   This message requests the MIF API to announce the availability of any
   provisioning domains configured on a particular interface.  The
   interface identifier must be specified.

   Upon receipt, the MIF API will iterate across the list of
   Provisioning Domains present for a particular interface, and will



Liu, et al.                Expires May 3, 2012                  [Page 9]

Internet-Draft              MIF API Extension               October 2011


   send a Provisioning Domain Announcement for each such Provisioning
   Domain.

   In addition, the MIF API will set a flag indicating that the
   subscriber wishes to know about new provisioning domains as they
   appear.  Subsequently, when a new Provisioning Domain appears, the
   MIF API will send a Provisioning Domain Announcement message to the
   subscriber.

   Finally, if a Provisioning Domain expires or is invalidated, the MIF
   API will send the subscriber a No Provisioning Domain Announcement
   message for that Provisioning Domain.

   In the event that an interface on which provisioning domains has been
   announced goes away, a No Provisioning Domain Announcement message
   will be sent for each provisioning domain that had previously been
   announced on that interface before the No Interface Announcement
   message is sent.

   Once a No Interface Announcement message has been sent, any
   subscriber that had subscribed to Provisioning Domain announcements
   for that interface will be automatically unsubscribed.

3.5.6.  Stop Announcing Provisioning Domains

   This message requests that the MIF API stop sending the subscriber
   Provisioning Domain Announcement and No Provisioning Domain
   Announcement messages.  The subscriber must indicate the interface
   for which it no longer wishes to receive Provisioning Domain
   announcements.

3.5.7.  Provisioning Domain Announcement

   This message is sent by the MIF API to the subscriber to indicate
   that a new Provisioning Domain has successfully been configured on an
   interface.  The announcement includes the interface identifier and
   the provisioning domain identifier.

3.5.8.  No Provisioning Domain Announcement

   This message is sent by the MIF API to the subscriber to indicate
   that an existing, previously announced provisioning domain has
   expired or otherwise become invalid, and can no longer be used.

3.5.9.  Announce Configuration Element

   This message is sent by the subscriber to request a specific
   configuration element from a specific provisioning domain.  A



Liu, et al.                Expires May 3, 2012                 [Page 10]

Internet-Draft              MIF API Extension               October 2011


   provisioning domain identifier must be specified.

   The MIF API will respond by iterating across the complete list of
   configuration elements for a provisioning domain, sending a
   Configuration Element Announcement message to the subscriber for each
   one.

   Additionally, if any Configuration Elements subsequently complete for
   a particular provisioning domain, the MIF API will send a
   Configuration Element Announcement message to the subscriber for each
   such element.  If a Configuration Element becomes invalidated after
   it has been announced, the MIF API will send a No Configuration
   Element message.

   If a provisioning domain expires or becomes invalid, the MIF API will
   iterate across the list of remaining configuration elements for that
   provisioning domain amd send a No Configuration Element Announcement
   message for each such configuration element.

3.5.10.  Configuration Element Announcement

   The Configuration Element Announcement message includes a
   Provisioning Domain ID and a Configuration Element Type, which can be
   one of the following:
      Config Element RA
      Config Element DHCPv6
      Config Element DHCPv4
      ...TBD...

3.5.11.  No Configuration Element Announcement

   The No Configuration Element Announcement message indicates that a
   previously valid configuration element for a provisioning domain is
   no longer valid.  The message includes a provisioning domain
   identifier and a configuration element type.

3.5.12.  Announce Address

   This message is sent by the subscriber to request announcements of
   valid IP addresses for a specific provisioning domain.  A
   provisioning domain identifier must be specified.

   The MIF API will respond by iterating across the complete list of
   configuration elements for a provisioning domain, sending a Address
   Announcement message to the subscriber.

   Additionally, if any new Address is subsequently configured on a
   particular provisioning domain, the MIF API will send an Address



Liu, et al.                Expires May 3, 2012                 [Page 11]

Internet-Draft              MIF API Extension               October 2011


   Announcement message to the subscriber for each such element.  If an
   address becomes invalidated after it has been announced, the MIF API
   will send a No Address Announcement message.

   If a provisioning domain expires or becomes invalid, the MIF API will
   iterate across the list of remaining configuration elements for that
   provisioning domain amd send a No Address Announcement message for
   each such address.

3.5.13.  Address Announcement

   The Address Announcement message includes single IPv4 or IPV6 address
   and a Provisioning Domain identifier, as well as the valid and
   preferred lifetimes for that IP address (IPv6 only).

3.5.14.  No Address Announcement

   The No Address Announcement message indicates that a previously valid
   address for a provisioning domain is no longer valid.  The message
   includes a provisioning domain identifier and an IPv4 or IPv6
   address.

3.5.15.  Get Configuration Data

   The Get Configuration Data message is sent to the MIF API, and
   includes a Provisioning Domain ID, a Configuration Element Type, and
   a Configuration Information Identifier.

   Configuration Information Identifiers:
      DNS Server List
      ...TBD...

   The MIF API searches the configuration database for the specific type
   of Configuration Element on the specified Provisioning Domain to see
   if there is any configuration data of the specified type.  If so, the
   MIF API sends a Configuration Data message to the subscriber;
   otherwise it sends a No Configuration Data message to the subscriber.

3.5.16.  Translate Name

   The Translate Name message is sent to the MIF API.  It includes a
   provisioning domain and a name, which is a UTF8 string naming a
   network node.  The message also includes a Translation Identifier,
   which the subscriber must ensure is unique across all outstanding
   name service requests.

   The MIF API begins a name resolution process.  As results come in
   from the name resolution process, the MIF API sends Name Translation



Liu, et al.                Expires May 3, 2012                 [Page 12]

Internet-Draft              MIF API Extension               October 2011


   messages to the subscriber for each such result.

   Name resolution can be handled by one or more translations systems
   such as local host table lookup, Domain Name System, NIS, LLMNR, and
   is implementation-dependent. **need to think about this

3.5.17.  Stop Translating Name

   This message is sent to the MIF API to indicate that the subscriber
   is no longer interested in additional results from a particular name
   translation process.  The message includes the Translation
   Identifier.

3.5.18.  Name Translation

   The MIF API sends a Name Translation message to subscribers whenever
   results come in from a name translation process being performed on
   behalf of the subscriber.  The Name Translation message includes the
   Translation ID generated by the subscriber, and an IP address
   returned by the translation process.  If a single translation result
   contains more than one IP address, or IP addresses of different
   types, the MIF API sends a single Name Translation message for each
   such IP address.

3.5.19.  Connect to Address

   The Connect to Address message contains an IP address, a provisioning
   domain identifier, and a connection identifier which the subscriber
   must ensure is unique.  The MIF API attempts to initiate a TCP
   connection to the specified IP address using one or more source
   addresses that are valid for the specified provisioning domain,
   according to the source address selection policy for that
   provisioning domain.

   If the connection subsequently succeeds, the MIF API will send a
   Connected message to the subscriber.  If it subsequently fails, the
   MIF API will send a Not Connected message to the subscriber.

3.5.20.  Connect to Address From Address

   The Connect to Address From Address message contains a source IP
   address, a destination IP address, a provisioning domain identifier,
   and a connection identifier which the subscriber must ensure is
   unique.  The MIF API attempts to initiate a TCP connection to the
   specified IP address using the specified source address.

   If the connection subsequently succeeds, the MIF API will send a
   Connected message to the subscriber.  If it subsequently fails, the



Liu, et al.                Expires May 3, 2012                 [Page 13]

Internet-Draft              MIF API Extension               October 2011


   MIF API will send a Connection Failed message to the subscriber.

3.5.21.  Connected

   The Connected message contains the connection identifier that was
   provided in a previous Connect to Address or Connect to Address From
   Address message sent by the subscriber.  It also contains an token,
   suitable for use with the connection API, for communicating with the
   end node to which the connection was established.

3.5.22.  Not Connected

   The Not Connected message contains the connection identifier that was
   provided in a previous Connect to Address or Connect to Address From
   Address message sent by the subscriber.  It also contains an
   indication as to what went wrong with the connection.


4.  Example Usage

   below is an example that shows how MIF API in use:






























Liu, et al.                Expires May 3, 2012                 [Page 14]

Internet-Draft              MIF API Extension               October 2011


          +-------+                                     +-------+
          |  APP  |                                     |  API  |
          +-------+                                     +-------+
              |          Announce Interfaces                |
              |-------------------------------------------->|
              |          Interface 1, eth0                  |
              |<--------------------------------------------|
              |          Announce PDs on Interface 1        |
              |-------------------------------------------->|
              |          PD 1                               |
              |<--------------------------------------------|
              |          Interface 2, wa0                   |
              |<--------------------------------------------|
              |          PD 2                               |
              |<--------------------------------------------|
              |          Announce PDs on Interface 2        |
              |-------------------------------------------->|
              |          PD 3                               |
              |DNS query 2001::1, host.example.com A,AAAA   |
              |DNS query 192.168.1.1,host.example.com A,AAAA|
              |DNS query 2001::1, host.example.com A,AAAA   |
              |-------------------------------------------->|
              |14. 2001::1 DNS response:                    |
              |    host.example.com                         |
              |    IN A 14.15.16.17                         |
              |    IN AAAA 2001:192:321::1                  |
              |                                             |
              |    2002::1 DNS response:...                 |
              |    192.168.1.1 DNS response:                |
              |    IN A 192.168.1.1                         |
              |<--------------------------------------------|
              | 15. SYN: 14.15.16.17 @ IF1                  |
              |     SYN: 2001:192:321::1 @ IF1              |
              |     SYN: 2001:192:321::1 @ IF2              |
              |     SYN: 192.168.1.1 @ IF1                  |
              |-------------------------------------------->|
              | 16. SYN+ACK @ 192.168.1.1  IF1              |
              |     SYN+ACK @ 2001:192:321::1  IF2          |
              |     SYN+ACK @ 2001:192:321::1  IF1          |
              |<--------------------------------------------|
              |                                             |

                                 Figure 2

   As described in the above communication model, the application first
   invoke the MIF API to query how many interfaces in the host. then,
   the application invokes MIF API to query how many networks attaches
   in each interface. application then invoke MIF API to query each DNS



Liu, et al.                Expires May 3, 2012                 [Page 15]

Internet-Draft              MIF API Extension               October 2011


   configuration on each interface's attached network. application then
   send DNS query to each DNS server on each network.  The DNS servers
   may return multiple IP address of the queried host name.  The
   application then try to connect to each IP addresses of the host by
   sending tcp SYN packet to each destination IP addresses through
   multiple interfaces.  Some of the destination IP address may return
   ACK packet some may not.  The application then chose a best
   connection based on certain criteria. for example, the criteria may
   based on the qulity of the link.


5.  Security Considerations

   TBD


6.  IANA Considerations

   None


7.  Acknowledgments

   The authors want to thank Teemu Savolainen from Nokia, Dayi Zhao from
   Bitway, Dave Thaler from Microsoft and others for their useful
   suggestions and discussions.


8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

8.2.  Informative References

   [I-D.scharf-mptcp-api]
              Scharf, M. and A. Ford, "MPTCP Application Interface
              Considerations", draft-scharf-mptcp-api-02 (work in
              progress), July 2010.

   [RFC3493]  Gilligan, R., Thomson, S., Bound, J., McCann, J., and W.
              Stevens, "Basic Socket Interface Extensions for IPv6",
              RFC 3493, February 2003.






Liu, et al.                Expires May 3, 2012                 [Page 16]

Internet-Draft              MIF API Extension               October 2011


Authors' Addresses

   Dapeng Liu
   China Mobile
   Unit2, 28 Xuanwumenxi Ave,Xuanwu District
   Beijing 100053
   China

   Email: liudapeng@chinamobile.com


   Ted Lemon
   Nominum
   Redwood City
   CA 94063
   USA

   Email: Ted.Lemon@nominum.com


   Yuri Ismailov
   Ericsson
   Stockholm
   Sweden

   Email: yuri@ismailov.eu


   Zhen Cao
   China Mobile
   Unit2, 28 Xuanwumenxi Ave,Xuanwu District
   Beijing 100053
   China

   Email: caozhen@chinamobile.com
















Liu, et al.                Expires May 3, 2012                 [Page 17]