| Network Working Group | D. Liu |
| Internet-Draft | China Mobile |
| Intended status: Informational | K. Yap |
| Expires: April 30, 2015 | |
| C. Perkins | |
| Huawei | |
| T. Sun | |
| H. Deng | |
| China Mobile | |
| October 27, 2014 |
Cloud Based Mobile Core Network Problem Statement
draft-liu-cloud-mobile-core-02
This document introduces a IP cloud based mobile core network architecture. The motivation and the key problems that need to be further studied by the community are analyzed. The purpose of this document is to call the community's attention and interest to study the key technologies and protocols to realize this cloud based mobile core network.
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The mobile network has been evolved from 2G, 3G and now the 4G network is being deployed by many operators. Traditionally, the mobile core network equipment is dedicated telecom equipment, many of them are based on dedicated hardware platform, e.g. CPCI. The core network equipment's software is normally tightly coupled with the hardware. The purpose of this dedicate hardware and software integrated approach is to achieve telecom level high performance and high reliability. But the consequence of this design approach is the lack of flexibility of the network. Current mobile network is facing the challenge of the booming of the mobile Internet. The mobile network not only facing the very fast increasing of the data traffic and also have to face the challenge from OTT applications. Those challenges require the mobile core network having more flexibilitys. This document proposes a cloud based mobile network architecture to meet those challenges.
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].
Current mobile network is facing the following challenge:
1. The fast increasing of the data traffic. According to Cisco's visual networking prediction,the mobile Internet traffic will increase 66% CAGR from 2012 to 2017. Such high volume of data traffic will not only put a lot of pressure to the wireless access network side but also give a lot of challenge to the mobile core network side. For example, in current mobility management architecture, both the Mobile IP protocol developed by IETF and the GTP protocol developed by 3GPP share a common idea that there will be one or more IP anchoring points that maintain the home address of the mobile node and its topological routable IP address. The fast increasing of the mobile data traffic will give much pressure to the mobile anchor point. IETF DMM working group was formed to tackle this problem by distributing of the anchor point. A more radical approach is that there is no anchoring point in the network, it will relay on the routing system or SDN to take care of the mobility management.
2. The lack of flexibility of network functionality. Although the telecom industry is trying to decouple the service and the network but we still can see that in current mobile network architecture it is very difficult to deploy a new service or upgrade the network's capability. Since currently, most of the mobile core equipment is build on the CPCI hardware platform and the software normally tightly coupled with the hardware platform. It is very difficult to change or upgrade the network equipment's functionality in an agile way. On the other hand, the mobile operators want to provide more intelligent and value added service other than to be a just dumb pipe providers. That will also require the mobile core network has the flexibility.
3. The lack of flexibility of service deployment. When the operator wants to deploy a new service, it is needed to make the network upgrade plan carefully and need to do the trial deployment in a small area to guaranty that the new service and network upgrading will not affect the production network. The whole process of a new service to be deployed normally takes several months even years.
4. The challenge of reducing the CAPEX and OPEX cost. The mobile operators need to lower both the CAPEX and the OPEX of their network, especially when they are facing the fast increasing of the data traffic. Dedicated hardware and tightly coupled software also makes the CAPEX and OPEX at a high level.
This section discuss the cloud based mobile core network architecture.
Cloud
...........
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( )))
((( +-----------+ )))
(( |Mobile Core| )))
((( +-----------+ )))
('..............')
|
| IP Transmit 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: Cloud based mobile core network architecture
In this architecture, the mobile core network is located in the cloud/data center. That could be the operator's private cloud. The access network is connected to the mobile core network through IP transmit network. The mobile core network could run in a virtualized platform in the cloud/datacenter.
The cloud based mobile core network architecture implies the 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 to 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 normally is located in the metro IP transmit network. In this case, the mobile node to Internet traffic should also go through from the Internet access point instead of go to the mobile core in the cloud.
However, in some deployment scenario, the operator may choose to put the mobile core cloud in the convergency 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.
Since the control plane and data plane are separated and the data plane is distributed, traditional mobility management can not 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.).
IETF DMM working group is currently specifying distributed mobility management protocol which maybe suitable for this cloud based mobile network architecture. The key features of distributed mobility management are as follows:
Network slicing is a technology that can 'slice' a physical network into different pieces. Each piece is logically independent from each other. One example of network slicing technology is FlowVisor. FlowVisor [FlowVisor] is based on open flow protocol, multiple open flow controller could be connected to the FlowVisor and the FlowVisor connect to the physical switches. The FlowVisor can translate the flow control command from the controller above the FlowVisor in to the flow control command specific to the network slice that allocated to this controller. For example, in figure 2, from controller A's perspective, it believes that it has the full control of all the physical network. Also from controller B's perspective, it also believe that it has the full control of all the physical network. Multiple controllers do not interfere from each other.By this way, multiple controller can share the same physical network and the physical network is sliced into multiple pieces.
+----------+ +----------+ +----------+
|Controller| |Controller| |Controller|
| A | | B | | C |
+----------+ +----------+ +----------+
| | |
+-----------------------------------------+
| |
| Flow Visor |
| |
+-----------------------------------------+
|
+-----------------------------------------+
| |
| Physical Network |
| |
+-----------------------------------------+
Figure 2: FlowVisor
Network slicing can provide a flexible network capability for the operator. For example, the operator can deploy a new service in a new network slice without worry about affecting the production network's service.
FlowVisor is only one example for network slicing and network virtualization. Furthermore, how to combine network slicing and mobility management in the cloud based mobile core architecture is an important topic need to be further studied.
Network auto-configuration is a way to simplify the network operation and reduce the network OPEX. In an ideal case, the mobile access network should be registered automatically to the mobile core network without manual configuration. IETF has defined CAPWAP for wireless access point control and configuration. However, how to keep the auto-configuration protocol compatible with existing mobile network protocols need to be further studied.
The cloud based mobile core network can provide open API to the service provider and other third party developers. This feature will faciliate the developers to use the ability of the network.
This document discusses the motivation and challenges of the cloud based mobile core network. There are several key points that need to be further studied by the community.
1. Innovative mobility management scheme that fulfils with the distributed data plane traffic routing and network slicing requirement.
2. Network slicing. FlowVisor is one example of network slicing technology that based on openflow. Further study should be made regarding how to virtualize the mobile core network.
3. Network auto-configuration. How to define a mobile network auto-configuration protocol while keeps the backward compatibility with current mobile network need to be further studied.
Security should be studied when design the cloud based mobile core network.
| [FlowVisor] | , , "FlowVisor: A Network Virtualization Layer", 2009. |
| [IEEE-802.11.2012] | , , "", March 2012. |
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. |
| [openflow] | , , "OpenFlow Switch Specification", 2012. |