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Versions: 00                                                            
Network Working Group                                             D. Liu
Internet-Draft                                                   H. Deng
Intended status: Informational                              China Mobile
Expires: January 09, 2014                                  July 08, 2013


            Mobility Support in Software Defined Networking
                       draft-liu-sdn-mobility-00

Abstract

   This document discusses the SDN mobility problem and potential
   solutions.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on January 09, 2014.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Terminologies . . . . . . . . . . . . . . . .   2
     2.1.  Conventions used in this document . . . . . . . . . . . .   2
     2.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Motivation of SDN mobility  . . . . . . . . . . . . . . . . .   2
   4.  SDN mobility problem analysis and potential solutions . . . .   3
     4.1.  Enhance SDN to support mobility tunnel handling.  . . . .   3
     4.2.  Routing based SDN mobility support  . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Software defined networking provides a very flexible way to process
   IP packets and flows.  It decouples the control and forwarding
   function of traditional IP appliance.  IP mobility support has been
   specified by IETF.  There is currently not much discussion regarding
   the mobility support in SDN network.  This document discusses the
   motivation, problem and potential solution of the mobility support in
   SDN network.

2.  Conventions and Terminologies

2.1.  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 [RFC2119].

2.2.  Terminology

   SDN: Software Defined Networking

3.  Motivation of SDN mobility

   IP mobility support has been specified in IETF for years.  Both
   [RFC2002], [RFC3775], [RFC5555],[RFC5213] share the similar idea that
   it introduce an anchoring point to maintain the mapping of the home
   address and routing address of the mobile node.  It uses tunnel to
   encapsulate the user traffic so that the application layer is not
   aware of the mobility event.




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   IP protocol has been used intensively in current cellular network
   architecture.  For example, in LTE network architecture, IP support
   is enabled in the data plane.  Also In the control plane and mobility
   supprot, IP moblitliy protocol is used.  Both S2a/S2b/S2c interface
   is specified that can based on IP mobility protocol.

   There is ongoing research work and discussions of using SDN in
   cellular network.  SDN can provide the IP packets processing ability
   for the cellular core network.  Mobility support is critical for the
   cellular core network.  If mobility can be supported by SDN, the
   cellular core network can be significantly simplified.  The data
   plane traffic routing can also be optimized.  The following figure
   shows an architecture of the cellular core network that build upon
   SDN concept.


           +--------------------+      +--------------+        +----------+
           |mobility management |      | Charging     |        | Policy   |
           +--------------------+      +--------------+        +----------+
           +----------|----------------------|----------------------|-------------+
           |                            controller                                |
           +----------------------------------------------------------------------+
           +---------------------------------|------------------------------------+
           |           forwarding and packet swithching function                  |
           +----------------------------------------------------------------------+
           +---------------------------------|------------------------------------+
           |                      wireless access network                         |
           +----------------------------------------------------------------------+


   Figure 1.  SDN based Mobile core network

4.  SDN mobility problem analysis and potential solutions

   The purpose of mobility management is to maintain the session
   continuity from the application's perspective.  Normally, when a
   mobile node change its attachment point, its IP address will be
   changed accordingly.  If there is no mobility support, the
   application layer session will be broken.  For example, TCP session
   can not survive when the source IP address changes.

   There are several potential ways for SDN network to support mobility.
   The following sections will discuss the potential solution in detail.

4.1.  Enhance SDN to support mobility tunnel handling.

   Current mobility protocol mainly follows the concept of mobility
   anchor.  Mobility anchor point maintain the mapping of home address



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   and routing address.  For example, in Mobile IP, the home agent
   maintain the mapping of home address and care of address.  When the
   care of address changes due to mobile node's movement, the foreign
   agent or the mobile node will send binding update request to the home
   agent to update the binding cache entry.  The foreign agent or the
   mobile node will set up bi-directional tunnel towards the home agent.
   All the user traffic will be encapsulated in the bi-directional
   tunnel.

   To enable SDN to support mobility, one potential solution is to
   enable the SDN controller and SDN forwarding function to support IP
   mobility protocol related tunnelling processing.

                           +-------------------+
                           |mobility management|
                           +-------------------+
                                     | API
                            +-----------------+
                +-----------|    controller   |------------+
                |           +-----------------+            |
                |                    |                     |
                |                    |                     |
                |                    |                     |
                |                    |                     |
                |                    |                     |
                | +--------------------------------------+ |
                | |                  |                   | |
             +---------+       +---------+        +----------+
             | FA/MAG  |       |  FA/MAG |        |  LMA/HA  |
             +---------+       +---------+        +----------+


   Figure 2.  Enhance SDN to support mobility tunnel processing

   The mobility management function could run on top of the controller.
   The controller controlls the forwarding function.  To support
   mobility, the mobility management function monitors the mobile node's
   movement event.  When the FA/MAG detects the mobile node's movement,
   it needs to update the binding cache entry that maybe maintained in
   the mobility management function.  The mobility management function
   then control the forwarding function(FA/MAG) to do the mobility
   tunnel processing.  When the packets arrives at the LMA/HA, the
   mobility management function will controll the forwarding function to
   decapsulate the packets and forward the packets to the Internet.

4.2.  Routing based SDN mobility support





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   SDN provides a very flexiable way of packet and flow processing.  It
   is in nature can react quickly on the routing changes of the network.
   When the mobile node changes its point of attachment, the forwarding
   function will notify the mobility management function running on top
   of the controller, the controller then calculate the forwarding rules
   based on the destination IP address of the IP packet.  The controller
   then push the forwarding rules to the forwarding function and the IP
   packet will be forwarded accordingly.  When the user session
   terminated, the mobility management function will delete the
   forwarding rules.  In this manner, the application lalyer session
   continuity will be guaranteed since the mobile node's IP address is
   not changed during the movement.

   There are lots of interesting problems need to be solved to make SDN
   support mobility.  For example, the forwarding function needs to
   detect the movement event of the mobile node and notify the
   controller and mobility management function in a timely manner.  A
   routing path needs to be set up from the MAG/FA to the Internet
   access point in a timely manner.  To achieve this, new protocol and
   mechnism may need to be defined in IETF.

5.  Security Considerations

   TBD

6.  IANA Considerations

   None

7.  References

7.1.  Normative References

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

7.2.  Informative References

   [RFC2002]  Perkins, C., "IP Mobility Support", RFC 2002, October
              1996.

   [RFC3775]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
              in IPv6", RFC 3775, June 2004.

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





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   [RFC5555]  Soliman, H., "Mobile IPv6 Support for Dual Stack Hosts and
              Routers", RFC 5555, June 2009.

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

Authors' Addresses

   Dapeng Liu
   China Mobile
   Unit2, 28 Xuanwumenxi Ave, Xuanwu District, Beijing 100053, China
   Email: liudapeng@chinamobile.com


   Hui Deng
   China Mobile
   32 Xuanwumen West Street
   Beijng, Xicheng District  100053
   China

   Email: denghui@chinamobile.com






























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