Control plane of Intelligent Optical Network

SDH is a very mature and strict transmission network system, it has been the birth of a wide range of application support, has become the world's core network of the main transmission technology. China from 1995 on the main line began to turn to the SDH network, istio architecture,China's SDH transmission network is to support the number of fixed telephone users in China as the world's first network of telephone users, the current operators of the metropolitan area network is mostly using SDH system.

Istio service mesh architecture

But in the development of SDH is also faced with time division multiplexing, fixed bandwidth allocation brings low efficiency, high cost, the technology is relatively complex and so on, so the optical network based on SDH system to the IP based Optical network evolution is the operator, equipment manufacturers are very concerned about. The Next Generation Network (NGN) is a softswitch-centric, intelligent OTN based transmission Optical Network, a simpler network enables service providers to provide cheaper bandwidth and allow users to quickly and timely capacity expansion.

Istio architecture diagram

Therefore, it is very important to develop a new generation of intelligent networks, that is, to support large capacity, small-granularity optical exchange, and also to be compatible with the current evolution and fusion of SDH networks in core or metropolitan networks. Whether in the core network or metropolitan Area Network development and application of a new generation of intelligent network, the key is to design a good control plane.

General requirements for control plane of Ason

A well-designed control plane architecture, while supporting faster and more accurate circuitry, should also provide business providers with better control over their networks. The control plane itself should be reliable, scalable, and efficient, and should be versatile enough to support different technologies, different business needs, and different divisions of the supplier's functionality (such as the different packaging of control plane components). Generally speaking, the control plane architecture should meet the following requirements:

Can be used for a variety of different transmission network technologies (e.g. SDH,OTN,PXC). For this purpose, it is particularly important that the control plane architecture separate and process technology-related aspects and technology-independent aspects.

Have sufficient flexibility to adapt to different network conditions. This requirement can be achieved by dividing the control plane into different components, allowing the supplier and the business provider to determine the location of these components, and also allowing the business provider to determine the security and policy control of these components.

In the cluster-based NGN, the crisis of circuit-switched network is obvious. For the major operators, the expectation of NGN is not to tear down the existing network to create an ideal NGN model, but how to evolve from the existing network to NGN, and strive to maintain the leading position in the increasingly fierce business market.  Obviously a standardized optical control plane is the basis of the control plane of Ason. A well-designed control plane can quickly and accurately establish circuit connections, enabling service providers to better control their networks. The control plane itself must be reliable, scalable, and efficient. The control plane structure should be adaptable to support different technical means, different business requirements and the capabilities provided by different device providers.

The control plane should be able to support the basic connectivity functions of the switching connection (SC) or soft permanent connection (SPC) in the transport network. The types of connection features include one-way point-to-point connections, bidirectional point-to-point connections, and bidirectional point-to-point connections. Different network organization and segmentation result in several different automatic configuration models.

Second, automatic configuration

Telecom industry has recognized the need for high bandwidth link automatic configuration, based on the existing infrastructure of operators, the potential of developing new products and future strategies, three different models can be selected.

1. Soft Persistent Link model

The Soft persistent link model (the Soft permanent circuit MODEL,SPC model) is based on the difference between the user or the terminal system and the network. In this model, there is no network management or control interoperability between the terminal system (client) and the network. The network management system at the top of the control plane is used to connect nodes at both ends of communication. Therefore, the SPC model is important for connecting legacy devices to the optical core, and ATM and framerely (FR) switching interfaces are connected to the optical core through a network management system. This model has been used in the permanent virtual circuit (SPVC) service of ATM and is recommended by the MPLS network.

2. User network interface Model

The user network interface model (the username network Interface model) is similar to ISDN. In these networks, services are initiated by a terminal system. A router network requests high-bandwidth connections from the optical network via uni.  In the UNI model, the terminal system does not understand the topology and resource conditions of optical networks, but simply requires the establishment or deletion of connections. In some network applications, clients request different routes for different connections. Because the network and the terminal system do not share the topological information, in order to satisfy the diversity demand of the terminal system, Uni must support the "diversification route".

3. Peer-to-peer model

In the Peer-to-peer model, the initiator's connection request is always for the peer network element, that is, the requester needs to be fully aware of the topology information. With this information, the connection initiator can select routes through the optical network according to a series of rules, such as the multiplicity of routes, minimum delay, maximum reliability, or minimum hop count.

The Peer-to-peer model is greatly affected by the IP network. In IP networks, routers can be viewed as peer entities of the optical-layer cross Connection (OLXC), sharing all information between OLXC and routers. This is consistent with the mplambdas of the IETF. Routers in separate subnets in the Peer-to-peer Model Act as peer entities of the optical network. However, not all information is required for all nodes, such as the IP routing table. Which range of information needs to be shared is still under study.

III. signaling and routing protocols and distributed network intelligence

The essence of a signaling system is the action that can be requested, the characteristics associated with the connection, the protocol used to deliver the action on the network, and the channel that carries the signaling message.

Create or delete connections, state queries, and attribute modifications as required, which are four basic actions for identifying optical networks. These features are required for connection requests, as well as customer and connection authentication, source and destination addresses and ports, and security objects.

Signaling and routing protocols and distributed network Intelligence many device/service providers recognize the importance of intelligent optical routing, and have jointly developed signaling and routing criteria, such as the Gmpls of the IETF (Internet Engineering Task Force) (Generalized Multiprotocol Label switching, mainly completes the discovery of the neighboring nodes, the broadcast of the link state, calculates and maintains the entire network topology structure, the path management and the control, calculates the route index value, protects and restores and so on function. ITU-T introduced a g.7713.1 based on Pnni in February 2002, which is the first draft of Ason.

The distributed intelligence of Optical network relies entirely on optical routing and Signaling Protocol, to replace the traditional use of centralized network management to achieve intelligent, distributed intelligent Network topology discovery, automatic circuit configuration, such as the main embodiment of distributed intelligence, and IP routing is different, optical routing is not routing and forwarding packets, Mainly to play the role of the circuit configuration, when the circuit is formed, only the path of management and control.

The optical routing signaling Protocol is an extension of the OSPF protocol in IP network, which keeps the topology map of the whole network on each network element, which provides the foundation for the optical network to realize distributed intelligence, and can provide the network intelligence and function as follows:

The topology of the whole network can be seen through a single network element, and the network can be monitored.

The network element and the network element may establish the circuit through the Protocol, also may by the configuration individual network element, realizes the End-to-end circuit configuration.

The path lookup is realized in the End-to-end circuit recovery, and the network element is restored according to the topology and the bandwidth condition when it needs to be restored to the end-to-end circuit.

Provide virtual capacity, through topology and calculation, you can achieve arbitrary cascade, wavelength binding, the formation of non-standard bandwidth (such as STS-6), to discontinuous, not even in the same fiber or light bandwidth can also cascade, when the capacity exceeds the bandwidth capacity of light waves, It is also possible to provide greater bandwidth capacity (such as 40gbit/s capacity) by means of light wave bundling.

Distributed intelligence distributes the network intelligence to the network element, instead of using the intelligence that the network management system concentrates on the network element configuration, the distributed intelligence has the following advantages compared with the intelligence formed by network management:

(1) The net element can know the network physics situation directly, the distributed intelligent implementation speed is fast, the network survival ability is strong.

(2) When there is an internal and Out-of-band network management failure, the intelligence based on NMS cannot be implemented, and distributed intelligence is not affected.