DMM Working Group                                               A. Yegin
Internet-Draft                                                  Actility
Intended status: Informational                                  D. Moses
Expires: January 1, 7, 2017                                           Intel
                                                                K. Kweon
                                                                  J. Lee
                                                                 J. Park
                                                           June 30,
                                                            July 6, 2016

                     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 in selectively
   providing IP session continuity and IP address reachability on a per-
   socket basis.

Status of This Memo

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   This Internet-Draft will expire on January 1, 7, 2017.

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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  . . . . . . . . . . . . . . . . . . . .   5
     3.4.  Conveying the Selection . . . . . . . . . . . . . . . . .   6
   4.  Backwards Compatibility Considerations  . . . . . . . . . . .   8
     4.1.  Applications  . . . . . . . . . . . . . . . . . . . . . .   8
     4.2.  IP Stack in the Mobile Host . . . . . . . . . . . . . . .   8   9
     4.3.  Network Infrastructure  . . . . . . . . . . . . . . . . .   9
   5.  Summary of New Definitions  . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9  10
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   In the context of Mobile IP [RFC5563][RFC6275][RFC5213][RFC5944],
   following two attributes are defined for the IP service provided to
   the 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 chaging 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 the IP 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 it 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 the IP session continuity and IP address

   It should be noted that in reality not every application may need
   those 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., DNS client) can
   survive without having IP session continuity support.

   Achieving IP session continuity and IP address reachability by using
   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 [I-D.ietf-dmm-requirements].  Therefore, IP
   session continuity and IP address reachability should be be provided
   only when needed.

   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.  Those 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, those higher-
   layer protocols are rendered useless because their operation is
   inhibited by the Mobile IP.  Since Mobile IP ensures the IP address
   of the mobile host remains fixed (despite the location and movement
   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 the applications running on the
   mobile host 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.  So 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

   Three types of IP addresses are defined with respect to the mobility

   - Fixed IP Address

   A Fixed IP address is an address assigned to the mobile host by the
   network with a guarantee to be valid for a
   very long time, regardless of whether it is being used in any packets 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 point-of-
   attachment to another (with a different subnet or IP prefix) while it
   is connected.

   Fixed IP address 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 assigned to the mobile
   host by the network with a guarantee to be
   valid through-out 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 subnet or IP

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

   - Non-persistent IP Address

   This type of IP address provides neither IP session continuity nor IP
   address reachability.  The IP address is obtained from the serving IP
   gateway and it is not maintained across gateway changes.  In other
   words, the IP address may be released and replaced by a new IP
   address when the IP gateway changes due to the movement of the mobile

   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 client and
   instant messengers, can utilize Non-persistent IP Addresses.  Even
   though they could very well use a Fixed of Session-lasting IP
   Addresses, the transmission latency would be minimized when a Non-
   persistent IP Address is used.

   The network creates the desired guarantee (Fixed, Session-lasting or
   Non-persistent) by either assigning an IP address (as part of a
   stateful IP address generation), or by assigning the address prefix
   (as part of a stateless address generation process).

3.2.  Granularity of Selection

   The IP address type selection is made on a per-socket granularity.
   Different parts of the same application may have different needs.
   For example, control-plane of an application may require a Fixed IP
   Address in order to stay reachable, whereas 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, and zero or more Fixed IP addresses may be
   configured on 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
   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.  In case an application
   requests one, the IP stack shall make an attempt to configure one by
   issuing a request to the network.  If the operation fails, the IP
   stack shall fail the associated socket request.  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 requested 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 out of the scope of this specification to define
   criteria for selecting to use available addresses or choose to
   request new ones.  It supports both alternatives (and any

   It is outside of the scope of this specification to define how the
   host requests a specific type of address (Fixed, Session-lasting or
   Non-persistent) and how the network indicates the type of address in
   its advertisement of addresses (or in its reply to an address

   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 the boot

   - 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 Selection

   The selection of the address type is conveyed from the applications
   to the IP stack in a way to influence the source address selection
   algorithm [RFC6724].

   The current source address selection algorithm operates on the
   available set of IP addresses when selecting an address.  According
   to the proposed solution, if the requested type IP address is not
   available at the time of the request, the IP stack shall make an
   attempt to configure one such IP address.  The selected IP address
   shall be compliant with the requested IP address type, whether it is
   selected among available addresses or dynamically configured.  In the
   absence of a matching type (because it is not available and not
   configurable on demand), the source address selection algorithm shall
   return an empty set.

   A Socket API-based interface for enabling applications to influence
   the source address selection algorithm is described in [RFC5014].
   That specification defines IPV6_ADDR_PREFERENCES option at the
   IPPROTO_IPV6 level.  That option can be used with setsockopt() and
   getsockopt() calls to set and get address selection preferences.

   Furthermore, that RFC also specifies two flags that relate to IP
   mobility management: IPV6_PREFER_SRC_HOME and IPV6_PREFER_SRC_COA.
   These flags are used for influencing the source address selection to
   prefer either a Home Address or a Care-of Address.

   Unfortunately, these flags do not satisfy the aforementioned needs
   due to the following reasons, therefore new flags are proposed in
   this document:

   - Current flags indicate a "preference" whereas there is a need for
   indicating "requirement".  Source address selection algorithm does
   not have to produce an IP address compliant with the "preference" ,
   but it has to produce an IP address compliant with the "requirement".

   - Current flags influence the selection made among available IP
   addresses.  The new flags force the IP stack to configure a compliant
   IP address if none is available at the time of the request.

   - The Home vs. Care-of Address distinction is not sufficient to
   capture the three different types of IP addresses described in
   Section 2.1.

   The following new flags are defined in this document and they shall
   be used with Socket API in compliance with the [RFC5014]:

   IPV6_REQUIRE_FIXED_IP /* Require a Fixed IP address as source */

   IPV6_REQUIRE_SESSION_LASTING_IP /* Require a Session-lasting IP
   address as source */

   IPV6_REQUIRE_NON-PERSISTENT_IP /* Require a Non-persistent IP address
   as source */

   Only one of these flags may be set on the same socket.  If an
   application attempts to set more than one flag, the most recent
   setting will be the one in effect.

   When any of these new flags is used, then the IPV6_PREFER_SRC_HOME
   and IPV6_PREFER_SRC_COA flags, if used, shall be ignored.

   These new flags are used with setsockopt()/getsockopt(),
   getaddrinfo(), and inet6_is_srcaddr() functions [RFC5014].  Similar
   with the setsockopt()/getsockopt() calls, getaddrinfo() call shall
   also trigger configuration of the required type IP address, if one is
   not already available.  When the new flags are used with
   getaddrinfo() and the triggered configuration fails, the
   getaddrinfo() call shall ignore that failure (i.e., not return an
   error code to indicate that failure).  Only the setsockopt() shall
   return an error when configuration of the requested type IP address

   The following new error codes are also defined in the document and
   will be used in the Socket API in compliance with [RFC5014].

   EAI_REQUIREDIPNOTSUPPORTED /* The network does not support the
   ability to request that specific IP address type */

   EAI_REQUIREDIPFAILED /* The network could not assign that specific IP
   address type */

4.  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

4.1.  Applications

   Legacy applications that do not support the new flags will use the
   legacy API to the IP stack and will not enjoy On-Demand Mobility

   Applications using the new flags must be aware that they may be
   executed in environments that do not support On-Demand Mobility
   feature.  Such environments may include legacy IP stack in the mobile
   host, legacy network infrastructure, or both.  In either case, the
   API will return an error code and the invoking applications must
   respond with using legacy calls without On-Demand Mobility feature.

4.2.  IP Stack in the Mobile Host

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

   If the network infrastructure supports On-Demand Mobility feature,
   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 address.  If an IP address was already
   allocated to the host, the IP stack uses it and may not request a new
   one from the network.

4.3.  Network Infrastructure

   The network infrastructure may or may not support the On-Demand
   Mobility feature.  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.

5.  Summary of New Definitions

   The following list summarizes the new constants definitions discussed
   in this memo:

    <netdb.h>              IPV6_REQUIRE_FIXED_IP
    <netdb.h>              IPV6_REQUIRE_SESSION_LASTING_IP
    <netdb.h>              IPV6_REQUIRE_NON_PERSISTENT_IP
    <netdb.h>              EAI_REQUIREDIPNOTSUPPORTED
    <netdb.h>              EAI_REQUIREDIPFAILED

    <netinet/in.h>         IPV6_REQUIRE_FIXED_IP
    <netinet/in.h>         IPV6_REQUIRE_SESSION_LASTING_IP
    <netinet/in.h>         IPV6_REQUIRE_NON_PERSISTENT_IP
    <netinet/in.h>         EAI_REQUIREDIPNOTSUPPORTED
    <netinet/in.h>         EAI_REQUIREDIPFAILED

6.  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.

7.  IANA Considerations

   This document has no IANA considerations.

8.  Acknowledgements

   We would like to thank Alexandru Petrescu, John Kaippallimalil, Jouni
   Korhonen, Seil Jeon, and Sri Gundavelli for their valuable comments
   and suggestions on this work.

9.  References

9.1.  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,

   [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,

9.2.  Informative References

              Chan, A., Liu, D., Seite, P., Yokota, H., and J. Korhonen,
              "Requirements for Distributed Mobility Management", draft-
              ietf-dmm-requirements-17 (work in progress), June 2014.

   [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,

Authors' Addresses

   Alper Yegin


   Danny Moses
   Intel Corporation
   Petah Tikva


   Kisuk Kweon
   South Korea

   Jinsung Lee
   South Korea


   Jungshin Park
   South Korea