Software Defined Networking (SDN) is a paradigm that emerged in the networking industry in order to mitigate the limitations proven by traditional networks, such as complexity, difficult management and configuration, or vendor dependency. SDN was adopted initially in campus networks, then in data centers, and now researchers are trying to introduce it in all of the aspects of a network, from optical domain, wireless transport networks to Internet exchange points. Last October, the Open Networking Foundation’s (ONF) Wireless Transport project completed the industry’s first multi-vendor Wireless Transport SDN Proof of Concept (PoC). Furthering ONF’s goal of promoting greater commercial adoption of SDN, the PoC was designed to encourage the development, testing, and implementation of an open source controller capable of managing a multi-vendor microwave network.
Over the past six months, the project developed and executed a second PoC at Telefónica’s German offices in Munich. Several entities that form the Wireless Transport project, including equipment vendors Ceragon, Ericsson, Huawei, NEC, and SIAE; integrators and application providers such as HCL, Tech Mahindra, highstreet technologies, and Wipro; and operators AT&T, Deutsche Telekom, and Telefónica joined forces to demonstrate the applicability of this information model in an SDN environment.
Wireless transport networks are a key component of existing network deployments. The need for capillarity (i.e., extension of the service reach) to provide the sufficient network coverage demanded by end users resides greatly on wireless transport networks connecting access nodes to aggregation domains. Being a huge area of investment by network operators, it is a desirable objective to simplify and facilitate the roll-out and run of this network segment.
The use cases for this PoC focused on the completeness and flexibility of the information modeling underlying the interfaces and controller implementation. For this PoC, the team used the NETCONF protocol, as it is a southbound interface (SBI) particularly designed for configuration tasks. The translation of the generic Unified Modeling Language (UML) information model into a YANG data model has been done by software, which is provided by ONF’s project Eagle, an open source information modeling code repository, enabling UML code to auto-generate YANG model code.
For the controller, the team leveraged OpenDaylight (ODL), as it has a model-driven approach, allowing the generation of an internal data structure from the YANG model loaded via its NETCONF SBI. This data structure is just loosely integrated with the ODL controller core, but it suffices to pass information between SBI and northbound interface (NBI). The NBI has been implemented as a RESTCONF interface. This allows the decoupling of controller and application from being on the same computer.
Several use cases were designed for demonstrating the validity and usefulness of the microwave information model. Based on these use cases, several SDN applications were developed, most of which were created as OpenDaylight-DLUX web applications and used RESTCONF interface for communicating with the SDN controller. These SDN applications included:
- Configuration Application for listing and modifying the configuration of the microwave devices. This application has been directly integrated into ODL’s user interface.
- The Aberrances Detection Application compares the present configuration of devices with content from a file, which is an extract of a planning data base. All configuration values are arranged in a table with values that deviate from the file highlighted for easy identification.
- The Configured Network Application is a graphical description of the presently configured capacities in the network. This application visualizes configurations that are intentionally differing from the initial planning. Connections, which are temporarily switched off for power savings, are an example for such differences.
- The Effective Network Application graphically shows capacities which are currently effective in the network. Adaptive modulation or link failures are examples for the effective capacity differing from the configured or installed ones.
- The Event Handling Application receives and lists the notifications which have been sent by the devices. This includes alarms as well as configuration change confirmations, for example.
A testing framework was developed to automate integration testing of the components from the many different sources. In the test environment at Telefónica, controller, applications, and mediators were organized in dedicated virtual machines. The virtual machines containing controller and applications were hosted on a dedicated server. Participants connected to these with their respective computers while the mediators ran on separate computer devices.
The testing of this PoC at Telefónica proved that all of the applications performed as designed on the different kinds of devices used in the testing environment. The tests demonstrated the advantages of having a common information model for the management and configuration of microwave devices, in the context of SDN. It is an important step in the adoption of SDN in wireless transport networks as all of the vendor devices could be managed through the same controller and applications through the identical SBI. What we are seeing from these PoCs is the flexibility and programmability of a multi-layer transport network controlled by a single open source controller, increasing the network’s efficiency and management. The team is energized by this PoC and looks forward to developing additional PoCs to further commercial adoption of SDN.