Learning notes on ASON Routing Protocol

At present, the ASON routing protocol is widely used. So I have studied the comprehensive description of the OSPF-Based ASON routing protocol. I will share it with you here, hoping it will be useful to you. With the development of related technologies in the information field, especially the powerful driving force of Internet on the Growth of data services, optical networks are required to adjust the logical topology of networks in real time and dynamically to achieve optimal resource utilization, it can provide users with various bandwidth services and applications quickly and with high quality.

It also provides more comprehensive protection and recovery functions, stronger interoperability and scalability. Automatically Switched Optical Networks (ASON) are upgraded from IP, SONET/SDH, and DWDM environments, it organically integrates the flexibility and efficiency of IP addresses, the protection capability of SONET/SDH, and the capacity of DWDM through an innovative distributed network management system to give more intelligence to existing optical networks, it improves the utilization of network resources and develops into an intelligent optical network capable of automatic switching, representing the mainstream direction of the intelligent optical network. As one of the core technologies of the ASON routing protocol, the routing technology plays an important role in realizing dynamic routing of connections. The routing protocol used by traditional IP networks is Open Shortest Path First (OSPF) protocol, which can achieve dynamic routing. The routing of ASON routing protocol requires more features and higher flexibility, generally using OSPF-TE routing protocol based on GMPLS extension.

New Features of ASON Routing Protocol

ASON routes have many new features compared with traditional IP routes. Data Forwarding in an IP network is a hop-by-hop process. You do not need to establish a connection first. The optical network data exchange based on circuit switching is end-to-end, and a connection needs to be established first. Each router in an IP network selects an independent route based on the destination address in the IP data packet. Each node must use the same network topology database and routing algorithm. In the optical network, route selection is provided when a request is made to establish a connection, and the existing services are not affected when the connection is established. The optical network routing protocol flexibly contains various new information. bandwidth statistics in the optical network are also simpler than those in the IP network, making it easier to manage bandwidth resources. The neighbor discovery process is the basic function of many domain IP routing protocols. Neighbor Discovery in optical networks is implemented by the automatic discovery mechanism, and also includes discovery of link-related attributes.

The routing structure of the ason Routing Protocol

In order to adapt to the development of ASON routing system, the relationship between the ASON routing protocol level and the SNPP of the sub-Network Group is presented in the ITU-T recommendation of ITU G.8080/Y.1304; g.7715/Y.1706 defines a protocol-independent method to describe the ASON routing technology, including the functional components of the ASON Routing Structure, path selection, route attributes, abstract information, and status chart transfer, ASON routing generally uses explicit routing, that is, channel selection is selected by the network operator or software scheduling tool. In the Switched Optical Network, the requested end-to-end optical channel connection has certain limitations. The channel selection for a connection request will adopt the constrained routing algorithm. The Routing Structure Component of the ASON routing protocol includes the routing controller RC), routing information database RDB), link resource manager LRM) and protocol controller PC ).

(RC): responsible for responding to the connection controller's requests for channel or route information to establish a connection, including exchanging route information with peer-to-peer RC, then, after querying the route information database, you can select the route query channel. At the same time, you are also responsible for the topology information SNP and their attributes required by the Delivery Management Network, routing Information Database): stores local topology, network topology, accessibility, Routing policy configuration, and other Information obtained through route Information exchange. RDB can contain the routing information of multiple routing domains. RDB provides RC with an accessible view. Link resource manager (LRM): LRM provides all SNPP link information to RC, and notifies RC of any state changes to the link resources it controls.

Protocol controller PC): The PC converts the routing primitive into a message of a specific routing protocol, so it is related to the Protocol. The PC also processes control information related to the routing protocol, which is used for the management and maintenance of route information exchange. The original signaling is transmitted between the connection controller and the PC, which is semantic transparent to the original information and used as external protocol information. Signaling information can be transmitted between two PCs. Among them, LRM, RDB and RC are not related to the Protocol, and PC is related to the Protocol. RC processes the abstract information used for routing. The PC processes protocol-related messages based on the reference points that pass through the information, such as E-NNI, I-NNI, and passes routing primitives to RC.

ASON routing protocol and Interface

There are three routing methods in the ASON Routing Protocol: hierarchical routing, source routing, and hop-by-hop routing. The main function of the routing part is to provide route information and route information distribution for the connection controller, which is mainly completed by the routing controller. The routing Controller is responsible for the routing in the routing domain and responds to the routing information required to establish a connection from the connection controller. This information can be end-to-end, such as source routing ), it can also be the next hop. To achieve network management, the topology information subnet node SNP and their abstraction) requests are responded.

In the ASON routing protocol, the route table request interface is one of the input and output interfaces of the route controller. This interface accepts an unresolved route element and returns a group of links in the domain in which the route controller is responsible. The answer format includes but is not limited to) Send a link by jump) and the source route full route ). Local Topology interface: this interface uses local topology information and local topology update information to configure route tables. This is the topology information of the region in which the routing Controller is responsible. Network Topology interface: this interface uses network topology information and network topology update information to configure route tables. This is the external simplified topology information of the domain that the routing Controller is responsible for, for example, the overall topology, it mainly uses the OSPF-based Inter-Domain Routing-DDRP. DDRP aims to provide an Inter-Domain route for Circuit Switched Optical Networks.

ASON Routing Protocol

OSPFOpen Shortest Path First, Open Shortest Path First) protocol is an internal gateway that establishes a link status database by notifying the status of network interfaces between routers to generate a Shortest Path tree, each OSPF router uses these Shortest Paths to construct a route table. OSPF is a type of Internet route selection protocol. It is also the most common route selection protocol used to build large-scale networks and is not vulnerable to harmful routing information. OSPF is a link-State routing protocol designed to run in a separate autonomous system AS). Each OSPF router maintains the same database to describe the AS topology. Through this database, a route table is calculated by creating a shortest path tree. When the topology changes, OSPF uses the minimum value of the route protocol traffic to quickly recalculate the path. OSPF supports multiple equal-cost routes, provides intra-domain routing capabilities, provides route protection at the additional layer, reduces route protocol traffic, and identifies all route protocol exchanges.

OSPF is a dynamic protocol. It can quickly detect topology changes in AS, such AS failed routing interfaces) and calculate a new self-circulating path after a period of convergence. The basic elements of OSPF include LSA link status announcement, link status database, communication between OSPF routers, discovery and maintenance of neighboring routers, Database Synchronization, and Route Selection calculation. OSPF can quickly converge and support larger interconnected networks. Therefore, major domestic and foreign router manufacturers provide routers that support the OSPF routing protocol, making OSPF one of the most widely used routing protocols.

Conclusion

The ASON routing protocol can improve the flexibility of resource configuration, reduce the switch granularity, improve the network efficiency, and meet various business service requirements. It is a perfect information transmission network. At present, domestic and foreign research institutions are investing in research, ITU-T and IETF also have some corresponding standards and draft proposed, ASON routing protocol has made great progress, however, there are still some problems in the ASON Routing Protocol that have not yet been resolved. The ASON routing technology is one of them. In this paper, the requirements of ASON routing and the basic framework and a routing protocol of ASON-based GMPLS OSPF-TE is described, further efforts should be made to study how to make OSPF-TE routing protocol more suitable for dynamic routing of ASON routing protocol, in order to reduce service blocking rate and improve network performance, saves investment in network resources and exchange devices.