SDN: From Theory to Reality
At present, the technological evolution and application innovation of software-defined networking (SDN) are accelerating and the industry is becoming increasingly vibrant. Equipment vendors, operators and research institutions around the world are putting more efforts into the research of SDN. The SDN technology has moved from theoretical discussion to practical deployment and industrialization. While beyond-100G WDM/OTN networks are being deployed, how to apply SDN to them will be key to future market competition.
The reason why SDN has come into spotlight is that traditional closed networks cannot meet service innovation demands. With the emergence of various innovative applications, a network should support rapid deployment of new services. However, due to lack of standards, open interfaces, and a heavy reliance on vendor products’ lifecycles, the existing networks can’t support rapid service deployment, thus hampering service innovation. Operators urgently need to extend SDN into their transport networks. SDN separates the control and data planes to enable logically centralized control and abstraction of the underlying infrastructure for applications, creating an open interfaces-based and programmable network that can respond to the fast changing business needs.
SDN-Based OTN Product
ZTE's ZENIC SDON is an open, flexible, efficient, intelligent and programmable optical network solution with an architecture as shown in Fig. 1.
The architecture of ZENIC SDON consists of three planes: a programmable optical transport plane, a controller plane, and an application plane.
The optical transport plane is based on a 100G or beyond-100G network. It has several programmability features: component programmability where the modulation, the number of subcarriers, and the spectrum width can be flexibly adjusted; node programmability where the switching granularity, type, and level for the nodes are programmable; and network programmability where not only network connection services (e.g. bandwidth size and type, transmission path and latency, and service quality and security level) but also the type, scale, and topology of the logical subnets that are created on the same physical network are all programmable.
The controller plane uses a hierarchical design (orchestration layer + domain control layer) to achieve centralized intelligent control of the network. It can also be flexibly extended to support multi-domain interoperability and unified management of the entire network.
As for the application plane, ZTE is committed to building an open platform. Customers can use application services developed by ZTE or develop the applications by themselves based on the open interfaces of the control layer, making service development and deployment faster.
The ZENIC SDON solution brings great value to the traditional optical networks by incorporating the SDN technology.
Differentiated Protection with SLA
A traditional optical network provides protection against a single link failure, and is not capable of automatic traffic rerouting upon multiple failures. However, the ZENIC SDON solution enables centralized control of entire network resources and automatic recovery from multiple failures. It supports automatic electrical layer scheduling based on the OTN electrical cross-connection, automatic optical layer scheduling based on the ROADM, and coordinated scheduling of the optical and electrical layers. The SLA policies can be defined based on specific service needs to improve service security.
On-Demand, Flexible Service Deployment
The ZENIC SDON solution provides on-demand services such as bandwidth on-demand (BoD), performance on-demand (PoD), and optimization on-demand (OoD), and supports fast service deployment for the L3, L2, L1, and L0 layers, reducing the service deployment time from days and hours to minutes and seconds and dramatically increasing resource utilization and service performance. The BoD provides real-time or scheduled bandwidth as needed to fully utilize the OTN pipeline resources and cope with bursting traffic. The PoD provides differentiated services to meet different latency, transmission quality, and SLA requirements. The OoD provides route optimization, traffic balancing, and online policy adjustment after a topology change.
Network Slicing (Optical VPN) for Fine Control
The innovative optical VPN (OVPN) solution provides enterprise clients with self-service virtual private network as well as higher level security guarantee. When the enterprise clients encounter faults on the leased networks, the OVPN automatically allocates additional network resources to ensure efficient communication, improving customer experience and reducing O&M workload. At the same time, the network slicing function can allocate network resources to different services, so as to optimize resource utilization while giving fine-grain control over bandwidth and latency.
Great Value from IP + Optical Synergy
The SDN-based IP/optical coordination solution enables pipeline resource pooling (the transport network being the resource pool) to satisfy the dynamic service requests from the IP layer. It has the following advantages:
● Resource pooling for reduced costs: The pipeline resources are dynamically adjusted in real time according to traffic flows, increasing the network utilization rate from 20–30% to 60–80% and reducing Capex.
● Resource elasticity: The whole bearer network as a resource pool allows for automatic increase or decrease of the bandwidth based on the service demands.
● Resource visibility for quantitative investment: The resources of the whole bearer network can be quantified and counted. That visibility can be used to quantify the investment according to changes in resource requirements and the trend analysis, thus further reducing Capex.
● Network optimized with reduced latency: Based on an SDN architecture, a hierarchical SDN controller is introduced to automatically implement unified planning and scheduling of resources across IP and optical networks for multi-layer optimal path selection. It supports cross-layer coordination and optimization, reduces the number of hops and latency, and enables pass-through operations when necessary to meet the requirements of ultra-low latency services such as 5G.
● Simplified O&M for improved efficiency: This solution supports functions such as one-click service launch, building any topology in an app, automated L0-L3 service provisioning with the provisioning time reduced from two weeks to two minutes, locating faults in a second with a multi-layer topology view, and automated service restoration.
● Coordinated protection for a robust network: The vPIPE platform shares all redundant resources, which can be provisioned on demand to complete fault recovery. For high-reliability services, the end-to-end 1+ 1 backup is provided. The backup paths avoid links that share the same shared risk link group (SRLG) as the primary paths to ensure complete separation between them.
Improved O&M Capabilities
The ZENIC SDON solution supports data sharing of network planning tools, maintenance tools, inspection tools, and evaluation and optimization tools to achieve online network planning and intelligent fiber cutover. Meanwhile, network-wide resources are optimized and defragmented for improved resource utilization and bearing capacity. Thus, automatic and simplified network management and operation can be enabled.
Since 2014, the SDN-based optical transport networks have gone from conceptual verification, laboratory testing to trials over existing networks, and are now moving towards commercialization. At the beginning of 2018, multiple operators at home and abroad began to deploy SDON solutions, advancing the evolution of the traditional optical transport networks towards programmable beyond-100G optical transport networks. It is believed that in the near future there will be widespread SDON deployments.
SDN, Beyond-100G OTN, open and programmable, on-demand flexible service deployment, IP+optical synergy, network slicing