Software-Defined Networking in Access Networks: Opportunities, Challenges, and Choices

Software-Defined Networking in Access Networks: Opportunities, Challenges, and Choices

Chen Tian (Huazhong University of Science and Technology, Wuhan, China), Jie Wu (Fudan University, Shanghai, China) and Haibin Song (Huawei, Nanjing, China)
Copyright: © 2015 |Pages: 11
DOI: 10.4018/IJWSR.2015010101


Software-Defined Networking proposes to fundamentally change the current practice of network control. The two basic ideas are Centralized State Control and Uniform Device Abstraction, which support the Software-Defined promise. SDN has made significant progress. The opportunities of SDN in carrier access networks have been largely ignored by both industry and academia. In access networks, Quality-of-Service (QoS) oriented bandwidth management is more critical; the flexible QoS provisioning could be the most important opportunity for SDN. In this position paper, the authors show that the unique characteristics of access networks pose significant challenges to the two basic ideas. Contrary to the common agreement on “match-action” abstraction, the authors argue that the object-oriented abstraction might be a better choice for access networks to make a better software-defined implementation.
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Software-Defined Networking (SDN) proposes to fundamentally change the current practice of network control (McKeown 2008; Shenker 2011). In recent years, there are significant research and implementation efforts for SDN from both industry and academia (Casado 2007; Sherwood 2009; Canini 2012; Monsanto 2013; Yu 2013; Jain 2013). The most prominent SDN achievement is the B4 Project (Jain 2013), where Google uses SDN to perform traffic engineering for its global inter-datacenter networks.

Shown in Figure 1 (Sezer&Scott-Hayward, 2013), the SDN architecture has 3 layers: Application layer, Control layer and Infrastructure layer. The philosophy of SDN is that basic state distribution primitives should be implemented only once rather than separately for every control task.

Figure 1.

SDN functional architecture

Leading by Open Networking Foundation (ONF), SDN promotes two basic ideas (Sezer&Scott-Hayward, 2013):

  • Centralized State Control: For Control layer, a physically separated and logically centralized control platform handles state collection from all devices, make decisions, and distributes the control state to them.

  • Uniform Device Abstraction: For Infrastructure layer, devices of the forwarding plane could be controlled by a uniform open interface, which also removes the danger of vendor lock-in.

These two ideas together support the Software-Defined promise in Application layer: a fully programmatic interface upon which developers could build network management applications on (Koponen&Casado, 2010).

SDN has made significant progress. ONF advocates OpenFlow as the standard southbound interface defined between the Control and Infrastructure layers. In Control layer, there are many controllers emerged such as NOX (Gude&Koponen, 2008), ONIX (Koponen 2010) and Maestro (Cai&Cox, 2010). The OpenDaylight project promises to unify the northbound API between the Control and Application layers (Gopal, 2013). An additional OpenFlow management and configuration protocol is also proposed to remotely configure the control channel between the controllers and switches.

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