Ending the Confusion About Software- Defined Networking: A Taxonomy

Transcription

1 Ending the Confusion About Software- Defined Networking: A Taxonomy This taxonomy cuts through confusion generated by the flood of vendor SDN announcements. It presents a framework that network and server virtualization architects can use to discuss how SDN can benefit their organizations by providing an architectural model to compare multiple vendors approaches. Key Findings Software-defined networking (SDN) is a new approach to designing, building and operating networks that focuses on delivering business agility while lowering capital and operational costs. It is far more than just a new set of APIs designed to replace command line interfaces for managing individual devices. SDN represents a shift from (per box) element-based control to network-based control. While some vendors equate SDN with network virtualization, network virtualization is simply one of the applications supported by SDN. Limiting the discussion of SDN to network virtualization limits the value that can be achieved and may steer you toward an inappropriate choice. Most Layer 4-7 services (which include security, application delivery controllers and WAN optimization) are not part of SDN (which is a Layer 2/3 construct). However, via orchestration applications, SDN can be used to automate service chaining for upper layer services, thereby reducing deployment errors and risk. Recommendations Begin to explore the potential benefits and risks SDN will bring your organization, but beware of SDNwashing, which relabels legacy approaches with the latest buzzwords. SDN has significant potential security impacts. Update your security strategy to incorporate new needs and opportunities brought by SDN. If you focus on the data center network first, be sure to involve server, virtualization, security and storage teams in the discussion to ensure a single approach is adopted. Adoption of SDN requires a new way of thinking that may threaten existing network engineers. Identify members of your team with the skills and vision to lead the evaluation process. Analysis SDN is a new approach to designing, building and operating networks that support business agility. SDN brings a similar degree of agility to networks that abstraction, virtualization and orchestration have brought to server infrastructure. In SDN architecture, the control and data planes are decoupled, network intelligence and state are logically centralized, and the underlying network infrastructure is abstracted from network appli cations and features. In addition, programmability enables external control and automation that allow for highly scalable, flexible networks that readily adapt to changing business needs (see Figure 1). 1

2 While a great deal of attention has been directed toward SDN in data center networks and service provider networks, it can also be applied to campus networks and enterprise WANs. Applicability and benefits vary by use case. Note: Network functions virtualization (NFV) is a service provider initiative that is sometimes linked to SDN. NFV aims to consolidate many network equipment types onto industry-standard servers, switches and storage to lower cost, improve efficiency and increases agility. At the core of SDN is the controller, which abstracts the network elements (physical and virtual) and topology and presents a logical representation of the network. This approach replaces element-based, box-at-a-time configuration with network control; that is, instead of hop-by-hop control, it provides end-to-end control. In its purest form, SDN directs traffic through the network from an originating point to a terminating point based on real-time status of all network elements and policies defined for each endpoint. This abstracted representation can then be programmatically manipulated by applications via a set of northbound APIs, such as the open-source Floodlight APIs. These applications include network virtualization, WAN traffic engineering, service chaining for Layer 4-7 services (see Figure 5) and automated adds/moves/changes/roaming for client devices. Rapid growth of the SDN market depends upon timely, broad support of a core set of APIs across multiple vendors controllers. This will provide operational consistency and application portability (a hedge against vendor lock-in), and spur a vibrant market for third-party application development. Figure 1 SDN Architecture FW = firewall, IDS = intrusion detection system, IPS = intrusion protection system, WAF = Web application firewall Source: Gartner (March 2013) 2

3 The controller interacts with the data plane devices (including physical switches and routers, and virtual switches embedded in hypervisors) via southbound protocols, such as OpenFlow or vendor-specific device control protocols. Switches and routers can be physical or virtual, and use of standard control protocols enables multivendor implementations. For example, one vendor could provide the controller; another, the switches; and a third, the routers. This is especially attractive to service providers since their IP networks often contain devices from multiple vendors, requiring a great deal of customization of operations support systems (OSS) for provisioning and management. Note: SDN is not simply new APIs on existing boxes that are used to automate the configuration of individual devices. SDN Deployment Models Three deployment approaches are possible: device, overlay and hybrid. For greenfield deployments, particularly when the cost of physical infrastructure and multivendor options are important, a device-based model will be common (see Figure 2). The biggest limitation is that this approach currently does not leverage existing Layer 2/3 network equipment. When rapid deployment over an existing IP network or when responsibility for the SDN environment is assigned to the server virtualization team, a tunnel-based overlay approach may be appropriate (see Figure 3). With this approach, the SDN endpoints are virtual switches that are part of the hypervisor environment. Figure 2 Device-Based SDN Deployment Source: Gartner (March 2013) The greatest limitations are that this approach does not address the overhead of managing the underlying infrastructure, debugging problems in an overlay can be complex, and it does not support bare-metal hosts. 3

4 Figure 3 Overlay-Based SDN Deployment vswitch = virtualized switch Source: Gartner (March 2013) The third approach combines the first two into a hybrid deployment (see Figure 4). This allows nondisruptive migration, with a path toward an eventual device-based design. Gateways link devices, such as bare-metal servers, that do not natively support overlay tunnels. Figure 4 Hybrid-Based SDN Deployment Source: Gartner (March 2013) 4

5 SDN Definition SDN is a new approach to designing, building and operating networks. An SDN has the following key components: The control plane is decoupled from the data plane and is logically centralized in an SDN controller to provide a single abstracted view of the underlying network topology and its state. This controller may be deployed as a cluster for high availability and scalability and, over time, east- and westbound APIs will emerge that enable multicontroller federation. Communication between network devices and the SDN controller (the southbound interface) use communi cation protocols that may be open, such as OpenFlow, or may be proprietary. Open, standardsbased protocols allow for multivendor interoperability and increase choice and competition while reducing the threat of lock-in. The SDN controller will support an open interface to allow external programmability of the environment for automation, control and feature enhancement (the northbound APIs). Use Cases Exploiting SDN Capabilities In a data center context, SDN is a component of the policy-driven data center. It provides the programmable connectivity required to link the network to other components within the data center, delivering a more integrated, functional system. For example, a provisioning application could specify that an instance of the CRM application must have the services delivered (as shown in Figure 5). Figure 5 SDN-Based Service Chaining WOC = WAN optimization controller, ADC = application delivery controller, WAF = Web application firewall Source: Gartner (March 2013) The provisioning application would then ensure traffic flows through the appropriate devices in the correct sequence. 5

6 In a service provider context, SDN might be leveraged to provide a common control plane across multiple vendors equipment, including provider edge router, session border controller, core router and optical transport/ wavelength division multiplexing nodes to build an agile, multitenant network that is a platform for value-added services. Possible service offering could include flexible bandwidth on demand, patch protection/restoration and multicasting. SDN promises easier integration with OSS/business support systems to increase service agility while reducing capex and opex. For more information, please visit the HP networking section at Gartner.com. Source: Gartner Research, G , Joe Skorupa, Mark Fabbi, Akshay Sharma, 12 March 2013 Featuring research from Build your Network Around your Business is published by HP Networking. Editorial supplied by HP Networking is independent of Gartner analysis. All Gartner research is 2012 by Gartner, Inc. All rights reserved. All Gartner materials are used with Gartner s permission. The use or publication of Gartner research does not indicate Gartner s endorsement of HP Networking s products and/or strategies. Reproduction or distribution of this publication in any form without prior written permission is forbidden. The information contained herein has been obtained from sources believed to be reliable. Gartner disclaims all warranties as to the accuracy, completeness or adequacy of such information. Gartner shall have no liability for errors, omissions or inadequacies in the information contained herein or for interpretations thereof. The opinions expressed herein are subject to change without notice. Although Gartner research may include a discussion of related legal issues, Gartner does not provide legal advice or services and its research should not be construed or used as such. Gartner is a public company, and its shareholders may include firms and funds that have financial interests in entities covered in Gartner research. Gartner s Board of Directors may include senior managers of these firms or funds. Gartner research is produced independently by its research organization without input or influence from these firms, funds or their managers. For further information on the independence and integrity of Gartner research, see Guiding Principles on Independence and Objectivity on its website, com/technology/about/ombudsman/omb_guide2.jsp. About Gartner Careers Newsroom Policies Site Index IT Glossary Contact Gartner 6