Internet DRAFT - draft-liu-sdn-mobility
draft-liu-sdn-mobility
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.
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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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