With the rapid development of the emerging services such as cloud computing, 4K video, VR, and Internet of Things, the traffic in the operators’ backbone network keeps increasing with the growth rate higher than that stated by Moore’s law. However, the traditional expansion is implemented by increasing network nodes and layers, which leads to soaring CAPEX and OPEX. With slow growth in revenues, the operators’ profit margins will steadily shrink. Meanwhile, in the cloud-based service era, the traffic model may have sudden changes when big events happen. So the network needs flexible adjustment and quick response to service change, which brings huge pressure to the existing network. The major operators are all actively exploring network architecture reconfiguration by the new technologies such as SDN/NFV. SDN-based IP+Optical synergy is the objective of backbone network architecture transformation.
ZTE proposes the philosophy of “pipeline resource pooling” in IP+Optical synergy solution similar to the calculating and storing resource pooling at data centers. It turns the physical ports on routers and optical network resource into a resource pool, and provides network resource based on demands for services. Thus the pipeline resource can be dynamically allocated in a real-time way based on the service traffic model, which can dramatically improve the resource utilization of IP network and optical network, and reduce the overall network construction costs.
Backbone Network Encounters Four Challenges
The existing backbone network in a overlay model is composed of IP/MPLS routers and WDM equipment. The IP network solves flexible networking and multipoint exchanges; the optical network solves large-capacity and ultra-long-distance transmission. Being independent of each other, they have different focuses. With the rapid service development, the network model encounters the following four challenges:
Challenge I: Low efficiency in cross-layer service provisioning and deployment. Since the IP network and optical layer are independent of each other, the service involving optical network resource adjustment needs to be provisioned collaboratively by multiple O&M departments, which results in low efficiency without a unified coordination.
Challenge II: cross-layer forwarding with low efficiency and high costs. The typical IP backbone network implements 6 times of forwarding, among which 4 times do not produce value. A great deal of passing-through traffic reduces the forwarding efficiency of the core routers. With traffic growth, the routers need to be continuously expanded, which causes high costs.
Challenge III: difficult protection without multi-layer coordination. The services are mapped to multiple layers including IP/MPLS layer, ODU electrical layer, and WDM optical layer. The planning must meet the performance and reliability requirements of every layer. However, the traditional layer lacks a unified planning tool to deal with the optical layer SRLG message that cannot be solved by IP layer. An optical layer failure may cause multiple failures in IP layer and poor service experience. Meanwhile, to guarantee the service reliability, both IP layer and optical layer provide repeated protection, which is a great deal of resource waste.
Challenge IV: inflexible network adjustment with no resilience. The Internet services change with events suddenly. Focusing on service and user experience, the network should be dynamically adjusted in a real-time way to meet the burst service demands. Without flexible adjustment, the existing network cannot dynamically adapt to the traffic model.
ZTE SDN-based IP+Optical Solution
To meet the above challenges, ZTE actively explores and proposes future-oriented SDN-based IP+Optical solution, so as to provide new ideas for backbone network reconfiguration.
Its overall architecture is as follows:
”IP+Optical” Pooling Building Efficient Bearer Network Architecture
Unified Control & Unified Planning
A hierarchical SDN controller is introduced to bring a centralized intelligent control system for IP and optical network, which significantly improves the network flexibility and openness. The HCO (Hierarchical Controller) coordinates the resource of IP and optical network. The dynamic synergy of IP and optical network can be achieved by the advanced IP+Optical synergy algorithm.
ZTE can provide the operators with customized IP+Optical multi-layer planning tool. Based on different user strategies, it automatically implements joint planning of IP and optical network, outputs optimal multi-layer path (including detailed path and abstract path), overall network construction cost, network construction costs of each layer, as well as network deployment and suggestions, which can help the operators improve network bandwidth & performance, and reduces the network construction costs. In the meantime, coordinative protection strategies can be established based on SRLG by multi-layer planning tool to improve the network reliability and reduce the risks.
One-button Provisioning and Quick O&M
With IP+Optical solution, ZTE can help the operators build a unified O&M system to implement quick service provisioning, network monitoring, and troubleshooting. Select the head end and tail end routers on the APP interface, configure some parameters, and the controller can automatically activate the service channel from L0 to L3, which dramatically simplifies the service deployment procedure and reduces the error probability. The coordinative controller can classify the huge amount of alarm messages, analyze and figure out the root alarm, so as to help the O&M staff to quickly locate the errors, solve them, and improve the operation efficiency of the network.
Direct Transmission through Optical Layer with Lowest Cost
It’s known that the major function of router P in the IP network is traffic forwarding, just like that of the optical network device. However, the optical network has low cost per bit, low consumption, and high bandwidth. So ZTE IP+Optical solution implements direct service transmission through optical layer without going through router P, which cuts router traffic forwarding, reduces router resource consumption, and improves the transmission efficiency.
Cloud-based Resilient Network
ZTE IP+Optical solution provides the operators with multi-layer BoD. The optical network can be a resource pool to provide resource on demand. The IP network can truly adapt to the services and implement service optimization without topology change. The network bandwidth can be automatically change based on service demands to solve network congestion and unbalanced traffic. Thus the entire network is resilient enough to meet the service development demands in the cloud era.
Applications and Visions
ZTE will continuously make exploration and researches in the field of IP+Optical in the future, and actively participate in ODL open source programs. The advantages of multi-layer resource optimization, network openness, and O&M simplification brought by SDN will further speed up the commercial application of SDN-based IP+Optical solution.