Network Working Group D.L. Liu
Internet-Draft China Mobile
Intended status: Informational H. Chan
Expires: September 04, 2014 Huawei Technologies
H. Deng
China Mobile
March 03, 2014

Cloud Based Mobile Core Network Problem Statement


This document discusses the deployment scenario of distributed mobility management. The purpose of this document is to trigger the discussion in the group to understnad the DMM deployment scenario and consideration from the operator's perspective.

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Table of Contents

1. Introduction

Distributed mobility management aims at solving the centralized mobility anchor problems of the tranditional mobility management protocol. The benefit of DMM solution is that the data plane traffic does not need to traverse the centralized anchoring point. This document discusses the potential deployment scenario of DMM. The purpose of this document is to help the group to reach consensus regarding the deployment model of DMM and then develop the DMM solution based on the deployment model.

2. 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].

3. Deployment Scenario and Model of DMM

As discussed in the DMM requirement document, the centralized mobility management has several drawbacks. The main problem of the centralized mobility management protocols is that all the traffic need to anchor to a centralized anchor point. This approach does not cause any problem in current mobile network deployment but in the scenario that will be discussed later in this document, centralized mobility management protocols will have many drawbacks and it is believed that DMM is more suitable in that scenario.

The main deployment scenario discussed in this document is divided into two types. The first one is the network function virtualization scenario. In this scenario, the mobile core network's control plane function is centralized in the mobile cloud. Apparently, deploying the data plane function also in the same centralized mobile cloud is not optimized from the traffic routing's perspective. Another deployment scenario is the SIPTO/LIPA scenario which is discussed in 3GPP. In this scenario, DMM can provide optimized traffic offloading solution.

4. Network Function Virtualization

This section discusses network function virtualization scenario, the associated control - data plane separation and the possible mobility management functions to support this scenario.

4.1. Network Function Virtualization Scenario

The network function virtualization scenario is shown in Figure 1.

             Mobile Cloud
            ('             ')
          (                )))
         (((  +-----------+ )))
        ((    |Mobile Core|    )))
        (((   +-----------+   )))
                    | IP Transit Network
              (           )) MN-Internet communication
             (           ^ ))
      ^ > > >(           ^  ))> > > > > > > > >
      ^       ((         ^  )                  v
      ^        (.........^.)                   v
      ^ +-------|     |  ^|                    v
      ^ |             |  ^+--------------+     v
      ^ |             |  < <             |     v  MN-MN communication
      ^ |             |    ^             |     v
+--------------+    +--------------+    +--------------+
|Access Network|    |Access Network|    |Access Network|
+--------------+    +--------------+    +--------------+
      ^                    ^                   v
      ^                    ^                   v
  +---------+         +---------+         +---------+
  |   MN    |         |    MN   |         |   MN    |
  +---------+         +---------+         +---------+

Figure 1: Network function virtualization deployment architecture

In this architecture, the mobile core network is located in the cloud /data center, which can be the operator's private cloud. The access network is connected through an IP transit network. The mobile core network can run in a virtualized platform in the cloud/datacenter.

4.2. Control and data plane separation

The cloud based mobile core network architecture implies separation of the control and data plane. The control plane is located in the cloud and the data plane should be distributed. Otherwise, all the data traffic will go through the cloud which is obviously not optimized for the mobile node to mobile node communication.

For the mobile node to Internet communication, the Internet access point is normally located in the metro IP transit network. In this case, the mobile node to Internet traffic should also go through the Internet access point instead of the mobile core in the cloud.

However, in some deployment scenario, the operator may choose to put the mobile core cloud in the convergence layer of IP metro network. In this case, the Internet access point may co-located with the mobile core cloud. In this case, the mobile node to Internet traffic may go through the mobile core cloud.

4.3. Mobility management functions

Since the control plane and data plane are separated and the data plane is distributed, traditional mobility management cannot meet this requirement.

Distributed mobility management or SDN based mobility management may be used in this architecture to meet the traffic routing requirement (e.g. MN to MN and MN to Internet traffic should not go through from the mobile core cloud.).

The traditional mobility management functions is not separating the data plane from the control plane. Basic mobility management functions include location management (LM) and Routing management (RM). The former is a control plane function. The latter can be separated into data plane routing management (RM-DP) and control plane routing management (RM-CP).

The data plane function is RM-DP which may also be called a Data Plane Anchor (DPA). The control plane functions include RM-CP and LM and may be called a Control Plane Anchor (CPA). Then the control plane functions in the cloud-based mobile core includes LM and RM-CP or CPA. They are of cause other functions in the control plane such as policy function. The distributed data plane may have multiple instances of RM-DP / DPA in the network.

               core network controller
                  |LM, RM-CP / CPA|

  +-------------+  +-------------+  +-------------+
  | RM-DP / DPA |  | RM-DP / DPA |  | RM-DP / DPA |
  +-------------+  +-------------+  +-------------+

Figure 2: Mobility management functions with data plane - control plane separation under one controller

When the control of the access network is separate from that of the core, there will be separate controllers as shown in Figure 3.

   Access network controller               Core network controller
       +---------------+                      +---------------+
       |LM, RM-CP / CPA|                      |LM, RM-CP / CPA|
       +---------------+                      +---------------+

+-------------+  +-------------+       +-------------+  +-------------+
| RM-DP / DPA |  | RM-DP / DPA |       | RM-DP / DPA |  | RM-DP / DPA |
+-------------+  +-------------+       +-------------+  +-------------+

Figure 2: Mobility management functions with data plane - control plane separation with separate control in core and in access.

5. SIPTO deployment scenario

Another deployment scenario is the SIPTO scenario which is discussed in 3GPP. DMM is believed to be able to provide dynamic anchoring. It allows the mobile node to have several anchoring points and to change the anchoring point according to the requirment of application. In SIPTO scenario, the gateway function is located very near to the access network and to the user. If using current centralized mobility management, the traffic will need to tunnel back to the previous anchor point even when the mobile node has changed the point of attachment to a new one.

6. Conclusion

This document discusses the deployment scenario of DMM. Two types of deployment scenario is discussed in this document. Further types of deployment scenario can be added to this document according to the progress of the group's discussion.

7. Security Considerations


8. IANA Considerations


9. Contributors

10. Acknowledgements

11. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[IEEE-802.11.2012] , , "", March 2012.

Authors' Addresses

Dapeng Liu China Mobile No.32 Xuanwumen West Street Beijing 100053, China EMail:
H Anthony Chan Huawei Technologies 5340 Legacy Dr. Building 3 Plano, TX 75024, USA EMail:
Hui Deng China Mobile No.32 Xuanwumen West Street Beijing 100053, China EMail: