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As the application of the GMPLS/ASON technology in intelligent optical networks began to scale, we began to realize that the construction and development of transmission networks not only included the transmission hardware technology, the unified network management and control of the transmission network are also two difficulties for network construction and equipment technology development. GMPLS/ASON Control Plane extends from SDH to WDM and CE, and even implements unified control at multiple transmission layers, which is an inevitable trend of technological development. With the help of the smart optical network control plane, the network reliability is improved, and new bandwidth services such as the OVPN of the optical virtual private network and the on-demand bandwidth BoD can be quickly provided, it can also improve network O & M efficiency and reduce costs. The article "Analysis of GMPLS/ASON development in Intelligent Optical Networks" prepared by Huawei Technology Co., Ltd. focuses on the development of GMPLS/ASON technology in Intelligent Optical Networks, and puts forward its own views and opinions, this will be of reference value for the future development of intelligent optical network technology.
In the Optical Network industry, the most frequently used word is intelligent Optical Network, and intelligent Optical Network mainly follows ASONAutomatic Switched Optical Network) or GMPLSGeneralized Multiprotocol Label Switching ).
As the application of the GMPLS/ASON technology in intelligent optical networks began to scale, we began to realize that the construction and development of transmission networks not only included the transmission hardware technology, unified management of transmission networks and unified control of transmission networks are two challenges for network construction and equipment technology development. Network management is basically developed in sync with the transmission hardware technology. Networking requires management, and network management is relatively mature. However, the control plane technology that was just emerging in the early 21st century started late. This article focuses on the development of control plane technology.
2 Introduction to smart Optical Networks
The main functions of the smart optical network control plane include automatic discovery, routing, and Connection Control. Automatic Resource and network topology discovery makes the network easier to expand or upgrade, and also facilitates maintenance and management. In addition, based on the routing and connection control functions, each transmission node with a control plane is, the service connection can be established or removed independently. When the network fails, the control plane can be rerouted, so that the network does not need to reserve dedicated protection bandwidth for each service, you can avoid the fault point and re-establish the connection, thus improving the network bandwidth utilization. In addition, through the combination of protection and recovery, optical networks can provide a wide range of business protection methods. Different businesses can choose different protection or recovery methods based on their reliability requirements. Currently, the GMPLS/ASON Control Plane running on the network consists of SDH/SONET devices, and the combination of GMPLS/ASON and SDH/SONET greatly improves the reliability of optical networks, and has been widely used.
Transmission technology is evolving rapidly. With the increasing variety of services, the bandwidth consumed by grouping services is increasing, and the Business granularity is also growing. In the age of group dominance, everyone's focus is on Carrier Ethernet and wavelength division, and they think that the data service needs a true and large-capacity transmission mode. The prospect of SDH/SONET devices originally designed for voice bearer seems to be getting increasingly gloomy, so some people question: is there a future for ASON? GMPLS/ASON Control Plane is not only based on SDH/SONET equipment, ITU-T defined ASON standard can be applied to SDH system and OTN. Similarly, the value of automatic discovery, routing, and Connection Control to the transmission network is also applicable to Carrier Ethernet devices.
The transmission of Large-particle businesses poses a challenge to the business guidance capability of WDM nodes. In recent years, the ROADMReconfigurable Optical Add-Drop Multiplexer technology has made some breakthroughs. MEMS-based technologies such as WSS have solved the issue of Optical wavelength reconfiguration, so as to a certain extent, it can realize flexible upper-lower and passthrough of optical wavelengths. Multiple manufacturers in the industry have released WDM systems with the optical layer reconfiguration feature. In addition, given that OTN has advantages in node definition and end-to-end management for Wavelength Division systems, OTN has become a hot topic and has begun to appear on commercial transmission devices.
The requirement for wavelength/sub-wavelength dynamic control comes with it, just as ASON is for SDH/sonet adm devices. The ASON/GMPLS basic flat control functions of WDM devices must include automatic discovery of network resources, network elements, optical fibers, links, and time slots, and automatic discovery of network topologies; the optical wavelength business and sub-wavelength business click to quickly provide basic functions such as optical layer wavelength-level Business Protection recovery, electrical layer sub-wavelength-level protection and recovery, and the combination of protection and recovery.
However, it is much more difficult to implement the GMPLS/ASON Control plane on the wavelength division system than the SDH/SONET control plane. Therefore, the control plane must consider some optical limitations on the optical layer, such as power, dispersion, and information-to-noise ratio. If the ODU1/ODU2 cross particles of OTN and the coexistence of OTN and ROADM are considered, the control plane must involve multi-layer control, the implementation is more complicated. The Application of GMPLS/ASON Control Plane to WDM systems is an inevitable trend. Some large foreign operators have published some white papers or joint bidding documents RFP, when it comes to the idea or demand for WDM-based GMPLS/ASON Control Plane, multiple manufacturers have already claimed to support WDM-based GMPLS/ASON Control Plane, however, there is no commercial verification yet.
On the metro side, the future transmission content will be mainly grouped. MSTP, Traditional Ethernet devices, and Carrier-class Ethernet devices, such as Carrier Ethernet, are coming soon. At present, Carrier Ethernet is particularly popular, because Carrier Ethernet defines Carrier-level attributes, it is an organic combination of "Carrier-level attributes + Ethernet businesses", or is a kind of "providing operation, maintenance, and management OAM similar to SDH, and has the new concept of low cost and flexibility of Ethernet. At the same time, TDM services, such as mobile voice and TDM leased lines, will still exist for a long time. Therefore, carrier-level Ethernet devices are grouped into kernels and have multiple transmission channels. Currently, several Metro Ethernet transmission technologies in the industry include MPLS, TMPLSTransport MPLS, PBTProvider Backbone Transport, and QinQ.
However, for carrier-level services, whether Packet or voice, its content has differentiated and clear requirements on QoS, and a highly reliable transmission network is also required. Therefore, it is necessary to introduce a control plane in the Carrier Ethernet network. But does it introduce MPLS unified transmission plane and control plane, or does it introduce GMPLS technology to build a separate control plane? From the perspective of technological development, MPLS has been applied, but it is difficult to extend MPLS to the end of the metro. From the perspective of the construction demand of the transmission network, GMPLS is more suitable for constructing the control plane of the transmission network. The main reason is that the transmission network constructed by WDM and SDH technology will exist for a long time, especially the value of WDM Technology will become even more promising.
Multiple transmission technologies will be applied to the network from long-distance relay to Metro access transmission. How can an end-to-end circuit at the transmission layer be quickly provided in such a hybrid network? The first requirement is, of course, the common network management of CE devices, SDH devices, and WDM devices. The second is the ability to achieve end-to-end unified control of CE, WDM, and SDH devices. Under this requirement, GMPLS is a better choice, because the protocol architecture of GMPLS completely defines the hierarchical and unified control of services from optical fiber to wavelength, sub-wavelength, TDM, Packet, etc, GMPLS can build a control plane independent of the transmission network-an independent control plane makes it easier to implement unified control of the layered network.
GMPLS/ASON Control Plane extends from SDH to WDM and CE, and even implements unified control at multiple transmission layers, which is an inevitable trend of technological development. With the help of the smart optical network control plane, the network reliability is improved, and new bandwidth services such as the OVPN of the optical virtual private network and the on-demand bandwidth BoD can be quickly provided, it can also improve network O & M efficiency and reduce costs. However, the beautiful vision is still subject to the actual conditions: manufacturers do not have powerful OSS and other network/business operation support systems; operators' internal business processing processes such as the relationship between data and transmission Departments) the application of new services is restricted. The Network Design Concept of smart optical networks needs to be changed, and network planning and engineering implementation must be changed accordingly, this transformation cooling the enthusiasm of many operators for the smart optical network. In addition, the standardization process also restricts the development of the GMPLS/ASON Control Plane, and there are technical difficulties to overcome and standardize, such as multi-layer LSP nesting and large-scale multi-vendor multi-domain networking.
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