Exploring O&M for ip+otn synergy

By Huang Hairong

Statistics show that over half of network traffic flows through core routers. Operators need to expand network capacity constantly to meet traffic growth. DWDM/OTN costs less than routers, though it can bear traffic of the same speed; it should therefore be utilized for heavy-traffic services whenever possible, with light-traffic services still carried by routers for statistical multiplexing. Traffic offload can help alleviate the pressure on routers and reduce the number of hops, while generating other benefits such as lowered costs and enhanced QoS. However, this is easier said than done. Services must be mapped between multiple layers, including IP/MPLS, ODUk, and WDM; such mapping must consider the performance and reliability of each layer, so that bandwidth demands are minimized over the entire network.

Typically, when bandwidth is insufficient for new service provisioning or service expansion, the router initiates a request to the transmission equipment through GMPLS-UNI. If the transport layer has sufficient resources, a connection is automatically established.

According to statistics from a European operator, a fault alarm at the transport layer increases ten-fold at the router layer. This added noise makes identification and resolution of the root problem onerous. Automatic alarm correlation and a unified alarm database are both needed so that low-priority cases are filtered out and troubleshooting efficiency is enhanced.

Multilayer network optimization should focus on traffic offload, while following a step-by-step process of manual, semi-automatic, and intelligent optimization.

Physical ports can be optimized manually while WDM equipment can make adjustments at the wavelength level, but both processes are still complex. Great skill is needed when adjusting key traffic nodes, as precise traffic adjustment is less efficient and less accurate, making coarse adjustment more suitable at this level.
Semi-automatic optimization simplifies planning and improves accuracy through traffic monitoring and offline optimization. It involves multiple layers and methods. The GMPLS-UNI, a key interface between the IP & optical layers, is implemented at this stage. Semi-automatic optimization requires tools that monitor traffic and optimize multiple layers, in addition to the GMPLS-UNI supported by routers and WDM devices.
Ideally, intelligent optimization for multilayer networks would be automatic and done in real time, yet this will require support from multi-layer PCE and offload servers; it will also require mature standards.
Huawei offers a multilayer network planning tool (ML-NPT) that facilitates IP+OTN synergy. With its advanced algorithms, this tool helps plan the IP and OTN layers automatically, and then exports data which includes optimal routing, TCO, costs of each network layer/node, and wavelength deployment. With Huawei ML-NPT, operators can use less costly devices to enhance bandwidth and performance. By working with the SRLG, this tool can enable protection synergy for both the IP and optical layers.
Unified O&M synergy

Unified management can be realized through a unified NMS that integrates the management systems used by various O&M departments, enabling timely service provisioning, monitoring, and troubleshooting. If an IP service error occurs, the unified NMS can help explore various routes, view lower-layer WDM service and fiber routing information, and then locate the faulty layer and route segment.