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DMM Working Group                                     H. Ali-Ahmad (Ed.)
Internet-Draft                                                    Orange
Intended status: Informational                                  D. Moses
Expires: January 12, 2014                                    H. Moustafa
                                                       Intel Corporation
                                                                P. Seite
                                                                  Orange
                                                             T. Condexia
                                                    University of Aveiro
                                                           July 11, 2013


          Mobility Anchor Selection in DMM: Use-case Scenarios
               draft-aliahmad-dmm-anchor-selection-01.txt

Abstract

   This document presents and discusses different use-case scenarios of
   mobility anchor selection in Distributed Mobility Management (DMM).

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-
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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 12, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



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   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.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Considered contexts  . . . . . . . . . . . . . . . . . . . . .  5
     3.1.  Mobile node context  . . . . . . . . . . . . . . . . . . .  5
     3.2.  Application context  . . . . . . . . . . . . . . . . . . .  6
     3.3.  Network context  . . . . . . . . . . . . . . . . . . . . .  8
   4.  Use-case scenarios . . . . . . . . . . . . . . . . . . . . . .  9
     4.1.  Extremely mobile nodes without any typical location  . . .  9
     4.2.  Mobile nodes with one or more typical locations  . . . . . 10
     4.3.  Fairly stationary nodes  . . . . . . . . . . . . . . . . . 12
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 16
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 16
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17



























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1.  Terminology

   IP-handover:

      a handover of a mobile node at the IP level resulting in an IP
      address change at the mobile node.

   New flow:

      a flow that did not undergo any IP-handover.

   Handover flow:

      a flow that did undergo one or more IP-handovers.

   New traffic:

      the data traffic of the new flows.

   Handover traffic:

      the data traffic of the handover flows.

   Current access router:

      the access router where the mobile node is currently attached at
      the IP level.

   DMM default mode of mobility anchor selection:

      new flows are always anchored at the current access router which
      acts as the mobility anchor for these flows after an IP-handover.



















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2.  Introduction

   Distributed Mobility Management (DMM) aims at overcoming the
   shortcomings of the existing IP mobility protocols, such as Mobile
   IPv6 [RFC6275] and Proxy Mobile IPv6 [RFC5213], that are considered
   centralized.  It brings the mobility anchor closer to the mobile
   node, down at the access routers level.  This is the enabler of a
   concept that is so-called dynamic mobility, where the mobile node
   changes its mobility anchor for new flows.  New flows are always
   initiated using the mobile node's current IP address which is
   configured using the prefix provided by the current access router.
   The data traffic of these flows is then routed optimally until the
   mobile node undergoes an IP-handover.  However, upon an IP-handover,
   tunneling mechanisms are needed with that access router, which is
   then considered the mobility anchor of those flows initiated using
   its prefix during the whole lifetime of those flows.  In what
   follows, this is considered the DMM default mode of mobility anchor
   selection.

   If most of the flows are short enough to not undergo one or more IP-
   handovers, it is expected that most of the data traffic is routed
   optimally.  However, this assumption is not always valid and the
   mobility anchor for new flows, when initiated, could be selected in a
   more appropriate manner.

   When a flow is initiated, it is assigned a mobility anchor that lasts
   during its whole lifetime.  Thus, selecting the most appropriate
   mobility anchor for a flow when initiated can significantly enhance
   the mobility management performance, e.g. less overhead, shorter end-
   to-end delay.  Thus, a DMM solution should allow selecting and using
   the most appropriate mobility anchor among a set of distributed ones
   [I-D.ietf-dmm-best-practices-gap-analysis].  In order to achieve
   this, different metrics and contexts should be taken into
   consideration.  Distributing the mobility anchor functionalities at
   the access routers level allows considering several contexts such as
   the mobile node's mobility context, the application context, and the
   network context.

   Hereafter in this document, the considered contexts are presented and
   then the different use-case scenarios are discussed.











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3.  Considered contexts

3.1.  Mobile node context

   The mobile node's mobility has an important effect on the mobility
   anchor selection.  For example, a mobile node with high mobility
   undergoes frequent IP-handovers.  When considering DMM default mode
   of mobility anchor selection, almost all the traffic of such mobile
   node is handover traffic, moreover, the number of simultaneous
   anchors and tunnels may increase.  On the other hand, flows of mobile
   nodes with low mobility are more likely to be initiated and
   terminated before undergoing an IP-handover.

   In addition, the mobile node's location with respect to the different
   mobility anchors influences selecting one of them for new flows.  For
   example, locating the mobility anchor as close as possible to the
   mobile node results in a shorter tunnel, and hence less tunneling
   overhead, when tunneling mechanisms are required.  The most
   appropriate mobility anchor is the closest one to the mobile node
   during the longer portion of the flow lifetime.  At the instant of
   initiating a new flow, the current access router is the closest one
   to the mobile node.  However, the mobile node may undergo an IP-
   handover and attach to another access router.  Whether the longer
   portion of the flow is before or after the IP-handover has an effect
   on selecting the most appropriate mobility anchor for this flow.

   Moreover, a mobile node may have one or more "typical locations"
   where it attaches to the network most of the time, e.g. at home.
   This helps expecting the mobile node's location for relatively long
   durations and, consequently, in selecting the most appropriate
   mobility anchor by using information about typical location(s).  Note
   that some statistics show that users spend more than 60% of their
   time at home and work [Cisco-VNI].

   Finally, the mobile node's attachments history is needed in order to
   take into consideration the mobile node's mobility and location as
   described above.














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   +---------+  +---------+  +---------+  +---------+
   | AR/MA 1 |  | AR/MA 2 |  | AR/MA 3 |  | AR/MA 4 |
   +---------+  +---------+  +---------+  +---------+
                                  |
                                  |
                               +----+                AR: Access Router
        ---- movement ---->    | MN |                MA: Mobility Anchor
                               +----+                MN: Mobile Node


              Figure 1: Mobile node's movement in DMM network


3.2.  Application context

   Based on the application, the need of IP continuity and the flow
   characteristics can be estimated.  While applications that require IP
   continuity cause the establishment of tunnels in the access network
   upon an IP-handover, applications that can tolerate an IP address
   change at the application layer, e.g.  SIP-based sessions, do not
   [I-D.ietf-dmm-requirements].  The mobility anchor selection is less
   important in the latter case due to the capability of changing the IP
   address.  In fact, there is no need for tunneling and hence no need
   for a mobility anchor since the application can tolerate any change
   in the IP address; hence, all the traffic is routed using standard
   routing schemes.

   In addition, the flow characteristics are highly dependent on the
   application.  Some applications generate in general long flows such
   as multimedia (e.g. video streaming), online gaming, large files
   downloading, etc. (see Table 1 below); others generate in general
   short flows such as TCP connections for HTTP and SMTP sessions.  Long
   flows are more likely to undergo one or more IP-handovers and
   therefore the mobility anchor selection can play an important role to
   enhance the mobility management performance.  On the other hand,
   short flows are more likely to be initiated and terminated before an
   IP-handover.

   In the following table, we present some examples on different types
   of applications.  For each application, we mention the expected (or
   probable) traffic and mobility characteristics as well as the
   possible types of devices used for such application.  The objective
   of this list of applications is to show later some possible real
   mapping(s) for the different use-case scenarios.







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   +-------------+------------+------------+-------------+-------------+
   | Application |   Traffic  |  Mobility  | User Device | Comments    |
   |             |    Type    |   Nature   |             |             |
   +-------------+------------+------------+-------------+-------------+
   |  RT Gaming  | Long flows | Stationary |   Laptop,   | For game    |
   |             |   with IP  |  or mobile |   tablet,   | consoles,   |
   |             | continuity | (depending | smartphone, | the device  |
   |             |     req    |  on game)  |     game    | and traffic |
   |             |            |            |   console   | characteris |
   |             |            |            |             | tics could  |
   |             |            |            |             |  be easily  |
   |             |            |            |             |  predicted  |
   |             |            |            |             |             |
   | Audio/Video | Long flows | Stationary | Smartphone, |             |
   | conferencin |   with IP  |  or mobile |   tablet,   |             |
   | g           | continuity |            |    laptop   |             |
   |             |     req    |            |             |             |
   |             |            |            |             |             |
   |     Live    | Long flows | Stationary |    Large    | If a large  |
   |  streaming  |   with IP  |  or mobile |  screen TV, | screen TV,  |
   |     IPTV    | continuity |            |   laptop,   | client is   |
   |             |     req    |            |   tablet,   | stationary. |
   |             |            |            |  smartphone | Otherwise,  |
   |             |            |            |             | client is   |
   |             |            |            |             | mobile      |
   |             |            |            |             |             |
   |     Waze    | Long flows |   Mobile   | Smartphone, |             |
   |             | without IP |            |  dedicated  |             |
   |             | continuity |            |   car GPS   |             |
   |             |     req    |            |   (future)  |             |
   |             |            |            |             |             |
   |    GoPro    | Long flows |   Mobile   |    GoPro    | A typical   |
   |             |   with IP  |            |    camera   | location    |
   |             | continuity |            |             | (Ski        |
   |             |     req    |            |             | resort)     |
   |             |            |            |             |             |
   |    Video    | Long flows | Stationary |    Mobile   |             |
   |    Report   |   with IP  |  or mobile | surveillanc |             |
   |             | continuity |            | e, HD camer |             |
   |             |     req    |            | a           |             |
   |             |            |            |             |             |










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   |    Video    | Long flows |   Mobile   |   Car TV,   | If the car  |
   |  streaming  |   with IP  |            |   tablet,   | is mainly   |
   | in vehicles | continuity |            |  smartphone | used in     |
   |             |     req    |            |             | specific    |
   |             |            |            |             | neighborhoo |
   |             |            |            |             | da typical  |
   |             |            |            |             |  location i |
   |             |            |            |             | srelevant   |
   |             |            |            |             |             |
   |  Camcorder  | Long flows | Stationary |   Camcoder  |             |
   |   download  |   with IP  |  or mobile |             |             |
   |             | continuity |            |             |             |
   |             |     req    |            |             |             |
   |             |            |            |             |             |
   |   HTTP and  |    Short   | Stationary | Smartphone, |             |
   |     SMTP    | flows with |  or mobile |   tablet,   |             |
   |   sessions  |     IP     |            |    laptop   |             |
   |             | continuity |            |             |             |
   |             |     req    |            |             |             |
   +-------------+------------+------------+-------------+-------------+

                                  Table 1

3.3.  Network context

   When a mobility anchor is assigned to a flow (when the flow is
   initiated), it acts as a mobility anchor for this flow the whole
   flow's lifetime.  It is responsible to forward the flow's data
   packets if the mobile node is physically attached to it.  It is
   responsible, in addition, to encapsulate and de-capsulate the flow's
   data packets if the mobile node is not attached to it and tunneling
   mechanisms are used.

   Even with distributed mobility anchors, the distribution of the
   active mobile nodes in the network is not necessarily even.  As a
   result, some mobility anchors are overloaded more than others.  It is
   then reasonable to take into consideration the estimated (or
   projected) level of load of the mobility anchors as well as the
   access network characteristics/resources when selecting one of them
   for a new flow (the metrics for measuring this level are left for
   specific implementations).










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4.  Use-case scenarios

4.1.  Extremely mobile nodes without any typical location

      Extreme mobility could be due to either a high mobile node's
      speed, or a small access router's coverage area, or both.


   Scenario 1: running applications generating typically short flows

      Short flows are more likely to be initiated and terminated before
      the mobile node undergoes an IP-handover.  Even if a flow
      experiences an IP-handover, it is expected that the flow does not
      last long after the IP-handover.  In other words, most of the
      mobile node's traffic is new traffic in this scenario.  As a
      result, the closest mobility anchor to the mobile node during the
      longest portion of a flow is its current access router.  It is
      recommended then to always anchor new flows at the current access
      router, which is the DMM default mode of mobility anchor
      selection.

      A well known example on short flows is the TCP connections for
      HTTP and SMTP sessions.

   Scenario 2: running applications generating typically long flows

      For extremely mobile nodes, it is more likely that a flow
      experiences an IP-handover soon after being initiated.  And since
      the flows are long-lived, it is expected that a flow lasts for a
      long duration after the IP-handover(s).  As a result, it could be
      said that most of the traffic is handover traffic in this
      scenario.  Whatever is the mobility anchor selection criterion,
      most of (almost all) the mobile node's data traffic needs
      tunneling mechanisms.  Thus, the mobility anchor selection cannot
      play a significant role regarding the route optimization or the
      tunneling overhead reduction.

      However, there are number of consequences regarding the control
      plane e.g. number of simultaneous anchors/tunnels for a mobile
      node and the related contexts and signaling loads.  First, let us
      consider the DMM default mode of mobility anchor selection.  Since
      new flows are always anchored at the current access router, each
      flow initiated between two consecutive IP-handovers is anchored at
      a different mobility anchor.  With extremely mobile node, long
      flows are expected to experience several IP-handovers and their
      mobility anchors are expected to be maintained for a long
      duration.  As a result, the number of simultaneous anchors/tunnels
      for a mobile node may increase as well as the related contexts and



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      signaling loads.  This affects the control plane negatively.

      As the DMM default mode does not achieve data plane optimization
      in the scenario described above, it is reasonable to consider a
      more centralized approach for mobility anchor selection in order
      to reduce the negative effects on the control plane.  If data
      packets are going to be tunneled in both cases, managing a single
      tunnel to a single mobility anchor would be better than managing
      several tunnels to several mobility anchors at the same time.

      It is worth mentioning that the discussion above is considering
      applications that require IP-address continuity.  On the other
      hand, there is no issue regarding the applications that allow an
      IP address change and manage mobility at the application layer
      since they do not need mobility anchors as mentioned before.

      Some examples on this scenario are (cf. Table 1) RT gaming, audio/
      video conferencing, live streaming IPTV, video report, video
      streaming in vehicles, and camcorder download.

   Scenario 3: running applications generating both long and short flows

      In this case, short and long flows can be distinguished when
      selecting a mobility anchor for a flow, based on scenario 1 and
      scenario 2.  Short flows are always anchored at the current access
      router; long flows are anchored based on a more centralized
      approach.  In this way, data packets of short flows are generally
      routed optimally and long flows do not introduce a large number of
      simultaneous anchors/tunnels.


4.2.  Mobile nodes with one or more typical locations


   Scenario 4: running applications generating typically short flows

      As the flows are short, there is no expected benefit from having a
      typical location.  If initiated when the mobile node is not at its
      typical location, such flows are more likely to end quickly before
      the mobile node goes back to its typical location.  Otherwise,
      they would be initiated and terminated when the mobile node is at
      its typical location.  As a result, the current access router is
      always the best mobility anchor for new flows and hence the DMM
      default mode of mobility anchor selection fits well this scenario.

      When the car is used mainly for short distance usages, Waze (cf.
      Table 1) could be an example on this scenario.




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   Scenario 5: running applications generating typically long flows

      In this scenario, having a typical location is expected to be
      beneficial for the mobile node's mobility anchor selection.  As
      mentioned before, the best mobility anchor for a flow is the
      closest one to the mobile node during the longer portion of this
      flow.  Then, the best mobility anchor for a flow could be in some
      cases that of the typical location even if the flow is not
      initiated there.  For example, if the mobile node initiates a long
      flow and then comes back (undergoing an IP-handover) quickly to
      its typical location, the longer portion of the flow would be
      after the IP-handover.  Thus, it is reasonable to select the
      typical location's mobility anchor for such flow when initiated.
      This results in tunneling part of the flow's data traffic when
      initiated but in routing optimally most of it afterwards.

      The analysis described above would be still valid if the mobile
      node has more than one typical location.  However, the benefits
      may not be in some cases as great as those of the one typical
      location scenario, depending on the mobile node's movements.  If
      there is no clear benefit from selecting one out of the mobility
      anchors, the network context (i.e. level of load on each mobility
      anchor) comes into play leaning towards selecting the mobility
      anchor that is less loaded.  Another refinement is to add the time
      of day to the statistics collection in the mobile node's
      attachments history.  If it is noticed that one of the typical
      locations is more popular than the others, this helps in selecting
      a mobility anchor according to the time of attachment.

      Some examples on this scenario are (cf. Table 1) RT gaming, audio/
      video conferencing, live streaming IPTV, GoPro, video report,
      video streaming in vehicles, and camcorder download.

   Scenario 6: running applications generating both long and short flows

      If it is possible, the short and long flows should be
      distinguished as follows.  While short flows are assigned the
      closest mobility anchor which is the current access router, long
      flows are assigned the typical location's mobility anchor.  In
      this case, the mobile node uses several IP addresses
      simultaneously e.g. the one related to the typical location for
      all long flows and the current IP address for short flows.  Hence,
      the mobile node needs a source address selection mechanism in
      order to distinguish between the different IP addresses when
      initiating a flow.






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4.3.  Fairly stationary nodes

   Scenario 7: running similar or different applications

      In fact, a fairly stationary node has one typical location for
      almost all the time.  The mobile node selects always the typical
      location's mobility anchor, which is the current access router
      most of the time.

      Some examples on this scenario are (cf. Table 1) RT gaming, audio/
      video conferencing, live streaming IPTV, video report, and
      camcorder download.







































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5.  Security Considerations

   TBD.
















































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6.  IANA Considerations

   This document has no actions for IANA.
















































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7.  Acknowledgements

   The authors would like to express their gratitude to Wu-Chi Feng and
   Philippe Bertin for having discussions, sharing thoughts, or
   providing reviews on anchor selection in DMM.














































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8.  References

8.1.  Normative References

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

   [RFC6275]  Perkins, C., Johnson, D., and J. Arkko, "Mobility Support
              in IPv6", RFC 6275, July 2011.

8.2.  Informative References

   [Cisco-VNI]
              Cisco Systems Inc., "Cisco Visual Networking Index: Global
              Mobile Data Traffic Forecast Update, 2009--2014", Cisco
              VNI , February 2010.

   [I-D.ietf-dmm-best-practices-gap-analysis]
              Liu, D., Zuniga, J., Seite, P., Chan, A., and C.
              Bernardos, "Distributed Mobility Management: Current
              practices and gap analysis",
              draft-ietf-dmm-best-practices-gap-analysis-01 (work in
              progress), June 2013.

   [I-D.ietf-dmm-requirements]
              Chan, A., Liu, D., Seite, P., Yokota, H., and J. Korhonen,
              "Requirements for Distributed Mobility Management",
              draft-ietf-dmm-requirements-05 (work in progress),
              June 2013.






















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Authors' Addresses

   Hassan Ali-Ahmad (Editor)
   Orange
   Email: hassan.aliahmad@orange.com


   Danny Moses
   Intel Corporation
   Email: danny.moses@intel.com


   Hassnaa Moustafa
   Intel Corporation
   Email: hassnaa.moustafa@intel.com


   Pierrick Seite
   Orange
   Email: pierrick.seite@orange.com


   Tiago Condexia
   University of Aveiro
   Email: tscondeixa@ua.pt


























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