© Springer-Verlag Berlin Heidelberg 2015 James J. (Jong Hyuk) Park et al. (eds.), Computer Science and Its Applications,

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Lecture Notes in Electrical Engineering 330, DOI: 10.1007/978-3-662-45402-2_170

Analysis on Study Trend and Technical Feature of Software-Defined Networking

Jinhyung Park1, Hyunhun Cho1, Joon-Min Gil2, and Byoung-Ju Yun3,*

1 Korea Institute of Science and Technology Information, Korea {ntoskr,hhcho}@kisti.re.kr

2 School of IT Engineering, Catholic University of Daegu jmgil@cu.ac.kr

3 School of Electronics Engineering, IT College, Kyungpook National University bjisyun@ee.knu.ac.kr

Abstract. Software Defined Network (SDN) emerged to fundamentally solve high cost and complexity in construction/operation/management of existing networks. Current SDN is in the initial stage of research /development and has been studied focusing on small and medium scale networks such as data center network, campus network and enterprise network. In addition, various approaches have been attempted to apply SDN to big scale networks such as the network of internet service provider(ISP). In this regard, this study will analyze the technical trend of SDN and possible problems, and present the future direction for development.

Keywords: Software Defnied Networking, NFV.

1 Introduction

Explosive growth of wireless data has been triggered by smart phone as well as fusion industry centering around cloud computing, M2M, smart TV and ICT, which, in turn, has required creation of new opportunity for growth in the area of network along with network enhancement through another technical innovation. However, existing network cannot live up to change in environment of the network market. In addition, demand for technical innovation from ICT area has emphasized the formation of ecosystem through interaction, system and evolutionary processes. Software-Defined Networking (SDN) is the trend that has appeared to overcome limitation of current network structure and to accommodate new requirements with introduction of innovative concept to existing network structure.

SDN has emerged as the practical alternative that can change existing paradigm by providing effective management function and flexibility of network configuration to cope with various changes in environment and converting hardware-oriented network to software-based one.

* Corresponding author.

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While SDN technology is in the initial phase of market formation currently, it has considerable potential since it is evaluated as the technology(knowledge base, standard) that can fundamentally change or innovate the market structure of existing global network industry. Accordingly, SDN has surfaced as the opportunity to reinforce competitive edge in Korea which shows absolute disadvantage in the area of network equipment. In this regard, this thesis will analyze technical trend related to SDN and possible problems, and present future direction of development.

2 Related Works

2.1 Software Defined Network

Software defined networking is new type of network where network control function is separated from packet forwarding and supports programming directly. In the past, control function of individual network equipment was not separated from hardware. However, SDN is the logical or virtual entity. As control area is separated into accessible computing device and migrated to computing device, it enables application that can manage or control network and use the network service.

In terms of logical structure of SDN technology, core function of network is concentrated on the control device based on software that controls the network on the whole. Accordingly, network appears as an application like one logical switch. Company and communication carrier can obtain the control ability on the network while not depending on the network supplier from a logical point of view of simplifying network design and operation. So, it is not necessary to understand and process over thousands of protocol standards any more and SDN simplifies the network equipment simply by controlling the control device. In particular, the network operator and manager can set the network more simply by using the programming type than setting through input of manual code line in various network devices distributed. In addition, IT department can reduce the time required for arranging new application and network service and can solve network problems real time by utilizing centralized intelligence of SDN control device. By concentrating the network on the control layer, SDN can provide flexibility to the manager in terms of network setting, management and security, and optimize the network competency through dynamic and automated SDN program. Such type enables the user to implement customized network service suitable for business goal, including routing, multi-cast, security, access control, bandwidth management, processor, storage optimization, service quality, amount of energy use and policy management of all forms.

2.2 Principle of SDN

SDN has 2 principles largely. First, SDN should deliver software definition. It means that data transfer function executed by hardware like switch should be controlled through open-type interface and software. Hardware executes specific operation by receiving [header template, transfer behavior] set from software. For example, packet can be “transferred“ or “discarded“ to certain network port. But, specific action is

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executed for the packet corresponding to ”header template“ of [header template, transfer behavior]. Here, header template may include wild card which means ”all packets“ or ”groups of certain packets“. Software definition transfer of SDN must include open-type interface and software, and OpenFlow technology corresponds to “open type interface”.

Second, SDN aims at abstracted global management or abstraction of global management. SDN should be able to develop leading network management tools by supporting abstraction of basic global management. For example, such abstraction tools may include global time of network, network situation(creation of new flow or change of topology), and the function to control network elements.

3 Analysis on Technical Trend

Different from existing networking technology, SDN and OpenFlow expands the role of software that performed the auxiliary role of existing network equipment, based on simple mechanism, and actively introduce the established concept in software such as distributed system, operating system and database, making efforts to configure ecosystem and structure that can enhance speed of innovation. While hidden behind the advantage of raising speed of innovation through maximization of software role is the risk that error of software module may exert a bad influence on overall network, SDN/OpenFlow analyzes SDN programming related technology trend into 3 viewpoints such as language, verification technique and virtualization to reduce the problem of software error.

3.1 SDN Language

Dedicated languages of SDN/OpenFlow currently active include FML, Frenetic, NetCore, Nettle and Procera, which were introduced recently through academy.

▪FML(Flow-based Management Language) : FML is the basic logic language for SDN suggested first and was developed for the purpose of defining the policy to be applied to enterprise network as declarative type.

▪Frenetic : Frenetic is based on database query language of declarative type same as FML. Frenetic provides single tier abstraction and modulation that cannot be provided in existing language, in order to overcome several limitations that may encounter in the stage of creating application for NOX controller, supports processing for competition conditions in terms of language runtime so that NOX application developer can focus more on forming the desirable works.

▪Nettle : Nettle is the FRP-based language that appears in the similar period as Frenetic, and is featured to handle discrete and continuous at the same time. Nettle can handle the event and message sent and received by OpenFlow controller and switch, in the unit of object abstracted as one stream. Nettle is based on Haskell language and has the following hierarchy.

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3.2 Verification Technique

Recently, studies on verification and testing for network directly related to SDN/OpenFlow are actively conducted. It should be handled as the important subject of research in that it can supplement the potential problems that may occur if SDN/OpenFlow is widely applied in the future. The following are the techniques introduced through NSDI, SIGCOMM and ONS in 2012.

▪NICE : model checking-based verification and test tool to detect the programming error of OpenFlow network. 4 heuristic techniques optimized for OpenFlow were developed and configured to substantially reduce the number of cases according to the sequence of event and pay more attention to find potential errors. NICE can be regarded as the main case of model checking application for SDN in that it does not simply apply the model checking technique which was mainly applied to real-time system or hardware design but supplements the problem of bigger status space that has been brought up consistently.

▪Kinetic : it defines the theoretical model of SDN mathematically, abstracts the network setting update process in the unit of packet and flow and provides the theoretical foundation that can strictly analyze the main attribute that should be guaranteed in the network in connection with several actions that may occur in the process of network update.

▪FortNOX : it is the expansion module developed to reinforce security function to existing NOX controller. It was implemented to cope with various security threat situations dynamically, and to naturally guarantee security related attribute in the course of adding the function for preventing collision between OpenFlow rules to SDN/OpenFlow controller. While existing SDN/OpenFlow technology guarantees the minimum security attribute that separates flow into several slice using the virtualization technique like Flowvisor and not interfered, FortNOX went one stage further to guarantee several security attributes that should be guaranteed in one slice and added to NOX, the rule optimization stage for detect and avoid collision between several rules and modules for performing role-based source certification before transferring OpenFlow command to network device.

3.3 Virtualization

SDN programming language and verification tools examined earlier may operate in close connection with SDN/OpenFlow environment. Platform for providing such environment treats the network virtualization as the main element technology. Thesis related to SDN virtualization, Open vSwitch, open source based software switch and OpenStack, an open interface based platform for cloud as well as virtualization related technology trend are briefly summarized.

▪Slice abstraction : new mechanism that supports the network abstraction unit of slice from the dimension of programming model so that virtual networks can replace the

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network virtualization technology that depends on mechanism of low level like VLAN based on non-interrupting model.

▪Open vSwitch : software switch for network virtualization that is actively developed as an open source project. It loads the function required to configure virtual network for data center or OpenStack based cloud.

▪OpenStack : could platform of the structure where heterogeneous modules in charge of computing, storage or network, interact with each other in message que or REST API based platform independent interface.

4 Limit of SDN

4.1 Scalability of SDN

Scalability of SDN in the initial stage of study remains as the dilemma since its scalability depends on its architecture and implementation method like web-based application. There are many functions of SDN that are difficult to implement actually among the functions of SDN expected by OpenFlow and SDN supporters. Main example includes global load balancing of flow in session unit that is handled at network. To implement this, one switch should treat every single flow that reaches over hundreds of thousand flows, which is difficult to implement in reality. hop-by-hop routing type is restricted by scalability. Some solutions use OpenFlow in the restricted area only due to scalability problem. For example, NVP of Nicira uses OpenFlow in controlling virtual switch in hypervisor(Xen, KVM) of cloud business operator. Switches in hypervisor managed by NVP are independent from switches in other area of management and do not interact with each other. In addition, NVP does not manage physical switch, but entrusts the NIC bonding or failover of server to linux kernel.

Solutions for scalability at present is to design structure in combination with existing technology such as Linux or IP network(RouteFlow, Overlay type routing) or to restrict the area of management like NVP.

4.2 Structural Problem

SDN controls the network by separating and concentrating the plane of control. However, it is natural that the system with distributed control is superior to the system with concentrated control in terms of overall performance. The reason why the router that uses IP protocol has been used in global internet for last 20 years is because routing processing operates distributed in the unit of node. On the other hand, SONET/SDH, Frame Relay and ATM used in the restricted area is the technology of depending on concentrated VC setting. If it exceeds over 50ms before concentrated controller determines the occurrence of failure in the link or node of network and sends the control command, it becomes impossible to restore the service while keeping the QoS of voice service. In addition, it is also difficult to implement the line

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card protocols that detect the link failure between 2 forwarding engines like BFD(Bidirectional Forwarding Detection), with concentrated type of controller. While NFC commercializing the OpenFlow switch and controller for the first time implemented such functions in the concentrated controller, it takes about 200ms to detour the broken links (differ depending on scale of network). Link detour problem can be solved by distributing certain intelligence or saving the calculated path in the network node. That is, while traditional WAN technology, SDH/SONET, uses the method of installing preliminary line for fast failover, it wastes half of bandwidth.

To avoid such structural problem of OpenFlow, Google uses OpenFlow only in G-scale network data center. OpenFlow controllers manage devices in the center only, use BGP and ISIS between remote data centers, and manage the flow using the traffic engineering technology similar to MPLS-TP in terms of function. NEC also reaches the limitation in real-time control of OpenFlow product. One OpenFlow controller can control up to 50 OpenFlow switches even if not operating line card protocols such as LACP(Link Aggregation control Protocol) or BFD(Bidirectional Forwarding Detection), or routing protocol with external device or STP(Spanning Tree Protocol). OpenFlow network interworks with external world through static root and static LAG(Link Aggregation Groups).

5 Development Direction of SDN

5.1 Combination of SDN and WIFI

Korean communication carriers have paid attention on SDN as the effective wire/wireless network operation management measure that can solve sudden rise of traffics. Main communication carriers have expressed their opinions at ‘SDN Special Conference’ that they may apply SDN technology which emerged as the major issue in network area, for reduction of network investment cost, improvement of operation efficiency and creation of new service. Overseas operators as well as domestic ones have applied or considered application to data center, policy-based flow control, wi-fi off loading or network management areas.

While dip packet inspection(DPI) technology has been utilized for optimization of video traffics, it is forecasted that intelligence much more enhanced than present can be implemented by applying SDN to policy-based flow control and giving instructions to all routers and that it can be the form of combining open flow controller and PCRF that takes charge of policy function in current environment. In addition, it is also expected that application of SDN into core network of base station may result in 20% cost reduction by separating the DU(Digital Unit) in charge of digital signal processing, virtualizing and utilizing into the telephone exchange. Like this, combination of SDN and WIFI is considered to be of great help in reducing network investment cost, improving operation efficiency and creating new service, contributing much to WIFI industry.

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5.2 Combination with Cloud Computing

Vision presented by VM ware, the leader in virtualization area, is Software Defined Datacenter(hereinafter SDD). SDD refers to the status when all infrastructures in the data center are virtualized. Virtualization has been mainly on the server up to now. Server virtualization is to put hypervisor(virtualization engine) on the server, and to run virtual machine over it. On the other hand, SDD takes all infrastructures such as storage, network and security system as well as server, as the target of virtualization. The person concerned in VM ware explained that “SDD is the status where all infrastructures are provided as virtual services, and the control of such data center is completely automated as software.” In addition, he explained that SDD would be the final stage of evolution for cloud computing. Cloud computing is proceeded in the order of standardization→virtualization →automation→SDD.

For example, the 1st stage is to integrate hardware into one standard like x86 system and the 2nd stage is to virtualize the server. The 3rd stage is to configure virtualized servers as pool and to automate the provisioning and orchestration. Cloud computing discussed at present is up to stage 3. VM ware emphasized that true cloud computing environment can be completed when it proceeds up to the stage 4 of SDD. Up to now, corporate IT system exists separately from each other. For example, ERP(enterprise resource planning) system and collaboration system have separate server, storage and network. Each application possesses its own infrastructure, which caused wastes of time and resource. There are lots of resources left in data center on the whole since infrastructure is configured based on peak time of each application. It takes lots of time to introduce new application as short as 2 or 3 month or as long as 3~4 years. On the other hand, SDD configures and virtualize the server, storage and network as standard equipment and provides capacity required by application.

The biggest advantage of SDD is the fact that a company can get out of the limitation of hardware. IT departments of companies have frequently encountered with limitation of hardware up to now when they try something new. For example, it was difficult to configure disaster recovery environment with different storage equipment. On the other hand, SDD means the status where something a company needs can be implemented immediately through software.

Given this, combination of SDN and cloud computing may result in considerable effects in terms of cloud computing.

6 Conclusion

As the network is advanced through technical innovation, existing network type showed limitation and a new technology called SDN emerged. SDN is the networking technology of next generation that can conveniently handle complicated operation management, network path setting and control through software programming.

We have analyzed the technical trend of SDN from 3 viewpoints of language, verification technique and virtualization. In addition, scalability, structural problem and data network issue, pointed out as limitation of SDN, were analyzed, and development through combination of wifi and cloud computing was suggested for future direction.

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The following are more macroscopic conclusions that can be proposed through such investigation and research. It is necessary to have the strategy to develop resources and competency by focusing on the area where supplementary knowledge(competency) is secured or competency can be build fast in terms of value chain that changes with introduction of SDN. In addition, it is also required to build the support system so that SDN supplier(star-up) can obtain necessary abilities and easily access the demand company in terms of policy. Lastly, it is urgently required to build the reference site with reliability. Accordingly, various consortium should be formed focusing on the voluntary market actors, which is exclusive in terms of value chain, motivation and ability, while providing the space of experiment where various market actors can voluntarily participate at the level of niche market.

References

[1] Rothenberg, C.E., et al.: Revisiting Routing Control Platforms with the Eyes and Muscles of Software-Defined Networking. In: HotSDN (August 13, 2012)

[2] ONF, Software-Defined Networking: The New Norm for Networks. White Paper (2012) [3] http://www.internet2.edu/network/ose [4] Software-Defined Networking: The New Norm for Networks,

https://www.opennetworking.org [5] Yu, J.: A Technical Trend and Prospect of SDN and OpenFlow (2013) [6] Levin, D., Wundsam, A., Heller, B., Handigol, N., Feldmann, A.: Logically centralized?

State distribution trade-offs in software defined networks. In: 1st Workshop on Hot Topics in Software Defined Networks, pp. 1–6 (2012)

[7] SDN/OpenFlow, http://itpro.nikkeibp.co.jp/openflow