DMM Working Group                                               A. Yegin
Internet-Draft                                                  Actility
Intended status: Informational                                  D. Moses
Expires: December 26, 2017                                         Intel
                                                                K. Kweon
                                                                  J. Lee
                                                                 J. Park
                                                                 S. Jeon
                                                 Sungkyunkwan University
                                                           June 24, 2017

                     On Demand Mobility Management


   Applications differ with respect to whether they need IP session
   continuity and/or IP address reachability.  The network providing the
   same type of service to any mobile host and any application running
   on the host yields inefficiencies.  This document describes a
   solution for taking the application needs into account by selectively
   providing IP session continuity and IP address reachability on a per-
   socket basis.

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Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document is subject to BCP 78 and the IETF Trust's Legal
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   ( in effect on the date of
   publication of this document.  Please review these documents
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . .   4
   3.  Solution  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Types of IP Addresses . . . . . . . . . . . . . . . . . .   4
     3.2.  Granularity of Selection  . . . . . . . . . . . . . . . .   5
     3.3.  On Demand Nature  . . . . . . . . . . . . . . . . . . . .   6
     3.4.  Conveying the Desired Address Type  . . . . . . . . . . .   7
   4.  Usage example . . . . . . . . . . . . . . . . . . . . . . . .   8
   5.  Backwards Compatibility Considerations  . . . . . . . . . . .  10
     5.1.  Applications  . . . . . . . . . . . . . . . . . . . . . .  10
     5.2.  IP Stack in the Mobile Host . . . . . . . . . . . . . . .  10
     5.3.  Network Infrastructure  . . . . . . . . . . . . . . . . .  10
   6.  Summary of New Definitions  . . . . . . . . . . . . . . . . .  11
     6.1.  New APIs  . . . . . . . . . . . . . . . . . . . . . . . .  11
     6.2.  New Flags . . . . . . . . . . . . . . . . . . . . . . . .  11
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   9.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  12
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  12
     11.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   In the context of Mobile IP [RFC5563][RFC6275][RFC5213][RFC5944], the
   following two attributes are defined for IP service provided to
   mobile hosts:

   IP session continuity: The ability to maintain an ongoing IP session
   by keeping the same local end-point IP address throughout the session
   despite the mobile host changing its point of attachment within the
   IP network topology.  The IP address of the host may change between
   two independent IP sessions, but that does not jeopardize its IP

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   session continuity.  IP session continuity is essential for mobile
   hosts to maintain ongoing flows without any interruption.

   IP address reachability: The ability to maintain the same IP address
   for an extended period of time.  The IP address stays the same across
   independent IP sessions, and even in the absence of any IP session.
   The IP address may be published in a long-term registry (e.g., DNS),
   and is made available for serving incoming (e.g., TCP) connections.
   IP address reachability is essential for mobile hosts to use
   specific/published IP addresses.

   Mobile IP is designed to provide both IP session continuity and IP
   address reachability to mobile hosts.  Architectures utilizing these
   protocols (e.g., 3GPP, 3GPP2, WIMAX) ensure that any mobile host
   attached to the compliant networks can enjoy these benefits.  Any
   application running on these mobile hosts is subjected to the same
   treatment with respect to IP session continuity and IP address

   It should be noted that in reality not every application may need
   these benefits.  IP address reachability is required for applications
   running as servers (e.g., a web server running on the mobile host).
   But, a typical client application (e.g., web browser) does not
   necessarily require IP address reachability.  Similarly, IP session
   continuity is not required for all types of applications either.
   Applications performing brief communication (e.g., ping) can survive
   without having IP session continuity support.

   Achieving IP session continuity and IP address reachability with
   Mobile IP incurs some cost.  Mobile IP protocol forces the mobile
   host's IP traffic to traverse a centrally-located router (Home Agent,
   HA), which incurs additional transmission latency and use of
   additional network resources, adds to the network CAPEX and OPEX, and
   decreases the reliability of the network due to the introduction of a
   single point of failure [RFC7333].  Therefore, IP session continuity
   and IP address reachability should be provided only when necessary.

   Furthermore, when an application needs session continuity, it may be
   able to satisfy that need by using a solution above the IP layer,
   such as MPTCP [RFC6824], SIP mobility [RFC3261], or an application-
   layer mobility solution.  These higher-layer solutions are not
   subject to the same issues that arise with the use of Mobile IP since
   they can utilize the most direct data path between the end-points.
   But, if Mobile IP is being applied to the mobile host, the higher-
   layer protocols are rendered useless because their operation is
   inhibited by Mobile IP.  Since Mobile IP ensures that the IP address
   of the mobile host remains fixed (despite the location and movement

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   of the mobile host), the higher-layer protocols never detect the IP-
   layer change and never engage in mobility management.

   This document proposes a solution for applications running on mobile
   hosts to indicate whether they need IP session continuity or IP
   address reachability.  The network protocol stack on the mobile host,
   in conjunction with the network infrastructure, would provide the
   required type of IP service.  It is for the benefit of both the users
   and the network operators not to engage an extra level of service
   unless it is absolutely necessary.  It is expected that applications
   and networks compliant with this specification would utilize this
   solution to use network resources more efficiently.

2.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

3.  Solution

3.1.  Types of IP Addresses

   Four types of IP addresses are defined with respect to mobility

   - Fixed IP Address

   A Fixed IP address is an address with a guarantee to be valid for a
   very long time, regardless of whether it is being used in any packet
   to/from the mobile host, or whether or not the mobile host is
   connected to the network, or whether it moves from one point-of-
   attachment to another (with a different IP prefix) while it is

   Fixed IP addresses are required by applications that need both IP
   session continuity and IP address reachability.

   - Session-lasting IP Address

   A session-lasting IP address is an address with a guarantee to be
   valid throughout the IP session(s) for which it was requested.  It is
   guaranteed to be valid even after the mobile host had moved from one
   point-of-attachment to another (with a different IP prefix).

   Session-lasting IP addresses are required by applications that need
   IP session continuity but do not need IP address reachability.

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   - Non-persistent IP Address

   This type of IP address does not provide IP session continuity nor IP
   address reachability.  The IP address is created from an IP prefix
   that is obtained from the serving IP gateway and is not maintained
   across gateway changes.  In other words, the IP prefix may be
   released and replaced by a new one when the IP gateway changes due to
   the movement of the mobile host forcing the creation of a new source
   IP address with the updated allocated IP prefix.

   - Graceful Replacement IP Address

   In some cases, the network cannot guarantee the validity of the
   provided IP prefix throughout the duration of the IP session, but can
   provide a limited graceful period of time in which both the original
   IP prefix and a new one are valid.  This enables the application some
   flexibility in the transition from the existing source IP address to
   the new one.

   This gracefulness is still better than the non-persistence type of
   address for applications that can handle a change in their source IP
   address but require that extra flexibility.

   Applications running as servers at a published IP address require a
   Fixed IP Address.  Long-standing applications (e.g., an SSH session)
   may also require this type of address.  Enterprise applications that
   connect to an enterprise network via virtual LAN require a Fixed IP

   Applications with short-lived transient IP sessions can use Session-
   lasting IP Addresses.  For example: Web browsers.

   Applications with very short IP sessions, such as DNS clients and
   instant messengers, can utilize Non-persistent IP Addresses.  Even
   though they could very well use Fixed or Session-lasting IP
   Addresses, the transmission latency would be minimized when a Non-
   persistent IP Addresses are used.

   Applications that can tolerate a short interruption in connectivity
   can use the Graceful-replacement IP addresses.  For example, a
   streaming client that has buffering capabilities.

3.2.  Granularity of Selection

   IP address type selection is made on a per-socket granularity.
   Different parts of the same application may have different needs.
   For example, the control-plane of an application may require a Fixed

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   IP Address in order to stay reachable, whereas the data-plane of the
   same application may be satisfied with a Session-lasting IP Address.

3.3.  On Demand Nature

   At any point in time, a mobile host may have a combination of IP
   addresses configured.  Zero or more Non-persistent, zero or more
   Session-lasting, zero or more Fixed and zero or more Graceful-
   Replacement IP addresses may be configured by the IP stack of the
   host.  The combination may be as a result of the host policy,
   application demand, or a mix of the two.

   When an application requires a specific type of IP address and such
   an address is not already configured on the host, the IP stack shall
   attempt to configure one.  For example, a host may not always have a
   Session-lasting IP address available.  When an application requests
   one, the IP stack shall make an attempt to configure one by issuing a
   request to the network (see Section 3.4 below for more details).  If
   the operation fails, the IP stack shall fail the associated socket
   request and return an error.  If successful, a Session-lasting IP
   Address gets configured on the mobile host.  If another socket
   requests a Session-lasting IP address at a later time, the same IP
   address may be served to that socket as well.  When the last socket
   using the same configured IP address is closed, the IP address may be
   released or kept for future applications that may be launched and
   require a Session-lasting IP address.

   In some cases it might be preferable for the mobile host to request a
   new Session-lasting IP address for a new opening of an IP session
   (even though one was already assigned to the mobile host by the
   network and might be in use in a different, already active IP
   session).  It is outside the scope of this specification to define
   criteria for choosing to use available addresses or choosing to
   request new ones.  It supports both alternatives (and any

   It is outside the scope of this specification to define how the host
   requests a specific type of prefix and how the network indicates the
   type of prefix in its advertisement or in its reply to a request).

   The following are matters of policy, which may be dictated by the
   host itself, the network operator, or the system architecture

   - The initial set of IP addresses configured on the host at boot

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   - Permission to grant various types of IP addresses to a requesting

   - Determination of a default address type when an application does
   not make any explicit indication, whether it already supports the
   required API or it is just a legacy application.

3.4.  Conveying the Desired Address Type

   [RFC5014] introduced the ability of applications to influence the
   source address selection with the IPV6_ADDR_PREFERENCE option at the
   IPPROTO_IPV6 level.  This option is used with setsockopt() and
   getsockopt() calls to set/get address selection preferences.

   Extending this further by adding more flags does not work when a
   request for an address of a certain type results in requiring the IP
   stack to wait for the network to provide the desired source IP prefix
   and hence causing the setsockopt() call to block until the prefix is
   allocated (or an error indication from the network is received).

   Alternatively a new Socket API is defined - getsc() which allows
   applications to express their desired type of session continuity
   service.  The new getsc() API will return an IPv6 address that is
   associated with the desired session continuity service and with
   status information indicating whether or not the desired service was

   An application that wishes to secure a desired service will call
   getsc() with the service type definition and a place to contain the
   provided IP address, and call bind() to associate that IP address
   with the Socket (See code example in Section 4 below).

   When the IP stack is required to use a source IP address of a
   specified type, it can use an existing address, or request a new IP
   prefix (of the same type) from the network and create a new one.  If
   the host does not already have an IPv6 prefix of that specific type,
   it must request one from the network.

   Using an existing address from an existing prefix is faster but might
   yield a less optimal route (if a hand-off event occurred after its
   configuration).  On the other hand, acquiring a new IP prefix from
   the network may be slower due to signaling exchange with the network.

   Applications can control the stack's operation by setting a new flag
   - ON_NET flag - which directs the IP stack whether to use a
   preconfigured source IP address (if exists) or to request a new IPv6
   prefix from the current serving network and configure a new IP

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   This new flag is added to the set of flags in the
   IPV6_ADDR_PREFERENCES option at the IPPROTO_IPV6 level.  It is used
   in setsockopt() to set the desired behavior.

4.  Usage example

   The following example shows the code for creating a Stream socket
   (TCP) with a Session-Lasting source IP address:

#include <sys/socket.h>
#include <netinnet/in.h>

  // Socket information
int              s ;                // Socket id

  // Source information (for secsc() and bind())
sockaddr_in6     sourceInfo         // my address and port for bind()
in6_addr         sourceAddress      // will contain the provisioned source
                                    // IP address
uint8_t          sc_type = IPV6_REQUIRE_SESSION_LASTING_IP ;
                                    // For requesting a Session-Lasting
                                    // source IP address

  // Destination information (for connect())
sockaddr_in6     serverInfo ;       // server info for connect()

  // Create an IPv6 TCP socket
s = socket(AF_INET6, SOCK_STREAM, 0) ;
if (s!=0) {
      // Handle socket creation error
      // ...
} // if socket creation failed
else {
       // Socket creation is successful
       // The application cannot connect yet, since it wants to use a
       // Session-Lasting source IP address It needs to request the
       // Session-Lasting source IP before connecting
     if (setsc(s, &sourceAddress, &sc_type)) == 0){
          // setting session continuity to Session Lasting is successful
          // sourceAddress now contains the Session-Lasting source IP
          // address

          // Bind to that source IP address
        sourceInfo.sin6_family = AF_INET6 ;
        sourceInfo.sin6_port = 0    // let the stack choose the port
        sourceInfo.sin6_address = sourceAddress ;
                                    // Use the source address that was

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                                    // generated by the setsc() call
        if (bind(s, &sourceInfo, sizeof(sourceInfo))==0){
             // Set the desired server's information for connect()
           serverInfo.sin6_family = AF_INET6 ;
           serverInfo.sin6_port = SERVER_PORT_NUM ;
           serverAddress.sin6_addr = SERVER_IPV6_ADDRESS ;

             // Connect to the server
           if (connect(s, &serverInfo, sizeof(serverInfo))==0) {
               // connect successful (3-way handshake has been completed
               // with Session-Lasting source address.
               // Continue application functionality
               // ...
           }  // if connect() is successful
           else {
               // connect failed
               // ...
               // Application code that handles connect failure and closes
               // the socket
               // ...
           } // if connect() failed
        } // if bind() successful
        else {
               // bind() failed
               // ...
               // Application code that handles bind failure and closes
               // the socket
               // ...
            } // if bind() failed
     }  // if setsc() was successful and of a Session-Lasting source address was provided
     else {
          // application code that does not use Session-lasting IP address
          // The application may either connect without the desired
          // Session-lasting service, or close the socket
     } // if setsc() failed
}  // if socket was created successfully

  // The rest of the application's code
  // ...

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5.  Backwards Compatibility Considerations

   Backwards compatibility support is required by the following 3 types
   of entities:

   - The Applications on the mobile host

   - The IP stack in the mobile host

   - The network infrastructure

5.1.  Applications

   Legacy applications that do not support the OnDemand functionality
   will use the legacy API and will not be able to take advantage of the
   On-Demand Mobility feature.

   Applications using the new OnDemand functionality must be aware that
   they may be executed in legacy environments that do not support it.
   Such environments may include a legacy IP stack on the mobile host,
   legacy network infrastructure, or both.  In either case, the API will
   return an error code and the invoking applications may just give up
   and use legacy calls.

5.2.  IP Stack in the Mobile Host

   New IP stacks must continue to support all legacy operations.  If an
   application does not use On-Demand functionality, the IP stack must
   respond in a legacy manner.

   If the network infrastructure supports On-Demand functionality, the
   IP stack should follow the application request: If the application
   requests a specific address type, the stack should forward this
   request to the network.  If the application does not request an
   address type, the IP stack must not request an address type and leave
   it to the network's default behavior to choose the type of the
   allocated IP prefix.  If an IP prefix was already allocated to the
   host, the IP stack uses it and may not request a new one from the

5.3.  Network Infrastructure

   The network infrastructure may or may not support the On-Demand
   functionality.  How the IP stack on the host and the network
   infrastructure behave in case of a compatibility issue is outside the
   scope of this API specification.

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6.  Summary of New Definitions

6.1.  New APIs

   setsc() enables applications to request a specific type of source IP
   address in terms of session continuity.  Its definition is:

int setsc (int sockfd, in6_addr *sourceAddress, sc_type addressType) ;

 - sockfd -        is the socket descriptor of the socket with which a
                   specific address type is associated
 - sourceAddress - is a pointer to an area allocated for setsc() to place
                   the generated source IP address of the desired session
                                   continuity type
 - addressType -   Is the desired type of session continuity service.
                   It is a 3-bit field containing one of the following
                   0 - Reserved
                   1 - FIXED_IPV6_ADDRESS
                   2 - SESSION_LASTING_IPV6_ADDRESS
                   3 - NON_PERSISTENT_IPV6_ADDRESS
                   5-7 - Reserved

setsc() returns the status of the operation:
 - 0 - Address was successfully generated
 - EAI_REQUIREDIPNOTSUPPORTED - the required service type is not supported
 - EAI_REQUIREDIPFAILED - the network could not fulfill the desired request

6.2.  New Flags

   The following flag is added to the list of flags in the
   IPV6_ADDR_PREFERENCE option at the IPPROTO6 level:

   IPV6_REQUIRE_SRC_ON_NET - set IP stack address allocation behavior

   If set, the IP stack will request a new IPv6 prefix of the desired
   type from the current serving network and configure a new source IP
   address.  If reset, the IP stack will use a preconfigured one if it
   exists.  If there is no preconfigured IP address of the desired type,
   a new prefix will be requested and used for creating the IP address.

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7.  Security Considerations

   The setting of certain IP address type on a given socket may be
   restricted to privileged applications.  For example, a Fixed IP
   Address may be provided as a premium service and only certain
   applications may be allowed to use them.  Setting and enforcement of
   such privileges are outside the scope of this document.

8.  IANA Considerations

   This document has no IANA considerations.

9.  Contributors

   This document was merged with [I-D.sijeon-dmm-use-cases-api-source].
   We would like to acknowledge the contribution of the following people
   to that document as well:

   Sergio Figueiredo
   Altran Research, France

   Younghan Kim
   Soongsil University, Korea

   John Kaippallimalil
   Huawei, USA

10.  Acknowledgements

   We would like to thank Wu-chi Feng, Alexandru Petrescu, Jouni
   Korhonen, Sri Gundavelli, Dave Dolson and Lorenzo Colitti for their
   valuable comments and suggestions on this work.

11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

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   [RFC5014]  Nordmark, E., Chakrabarti, S., and J. Laganier, "IPv6
              Socket API for Source Address Selection", RFC 5014,
              DOI 10.17487/RFC5014, September 2007,

   [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,

11.2.  Informative References

              Jeon, S., Figueiredo, S., Kim, Y., and J. Kaippallimalil,
              "Use Cases and API Extension for Source IP Address
              Selection", draft-sijeon-dmm-use-cases-api-source-06 (work
              in progress), March 2017.

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002,

   [RFC5213]  Gundavelli, S., Ed., Leung, K., Devarapalli, V.,
              Chowdhury, K., and B. Patil, "Proxy Mobile IPv6",
              RFC 5213, DOI 10.17487/RFC5213, August 2008,

   [RFC5563]  Leung, K., Dommety, G., Yegani, P., and K. Chowdhury,
              "WiMAX Forum / 3GPP2 Proxy Mobile IPv4", RFC 5563,
              DOI 10.17487/RFC5563, February 2010,

   [RFC5944]  Perkins, C., Ed., "IP Mobility Support for IPv4, Revised",
              RFC 5944, DOI 10.17487/RFC5944, November 2010,

   [RFC6275]  Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
              Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
              2011, <>.

   [RFC6824]  Ford, A., Raiciu, C., Handley, M., and O. Bonaventure,
              "TCP Extensions for Multipath Operation with Multiple
              Addresses", RFC 6824, DOI 10.17487/RFC6824, January 2013,

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   [RFC7333]  Chan, H., Ed., Liu, D., Seite, P., Yokota, H., and J.
              Korhonen, "Requirements for Distributed Mobility
              Management", RFC 7333, DOI 10.17487/RFC7333, August 2014,

Authors' Addresses

   Alper Yegin


   Danny Moses
   Intel Corporation
   Petah Tikva


   Kisuk Kweon
   South Korea


   Jinsung Lee
   South Korea


   Jungshin Park
   South Korea


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   Seil Jeon
   Sungkyunkwan University
   South Korea


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