Introduction to the integration of smart optical networks and Traditional transmission networks (1)

With the gradual application of smart optical network ASON, the transmission network will gradually increase the number of intelligent network elements. As operators have invested heavily in the traditional SDH network, in order to protect the original investment and realize the smooth evolution of the traditional optical transmission network to ASON, the intelligent network and traditional devices will coexist for a long time, the interoperability between the two is inevitable. Therefore, the interconnectivity and convergence between ASON and traditional SDH networks will be the key factor that determines the construction of ASON.

1. ASON Interface

ITU-T ASON standard mainly defines the user network interface UNI), network node interface NNI), Connection Control Interface CCI), network management interface NMI ). The main impacts on the convergence of New and Old networks are UNI and NNI. 1.

1.1 user network interface UNI)

UNI is the optical interface between the core optical network and its customer equipment edge electrical equipment. It is an important symbol of the overlapping network model and also a signaling interface between different domains and different layers. Through this interface, optical networks and electrical devices can be connected, and electrical devices can dynamically acquire, cancel, and modify Optical Bandwidth Resources with certain features. Generally, the basic information transmitted through this interface should include call control, resource discovery, Connection Control, and connection selection.

UNI does not support routing. Its main tasks include connection establishment, connection removal, status information exchange, automatic discovery, and user service transmission. Currently, the 0IF UNI protocol is the most complete and mature standard protocol in the industry. It not only develops a complete set of feasible UNI signaling protocols RSVP or LDP) control CHannel implementation and maintenance, as well as the corresponding frame encapsulation standards. It also provides a set of service discovery and topology discovery mechanisms.

1.2 network node interface NNI)

NNI is used to exchange information within the control layer. To avoid exposing the internal information of the sub-network to an untrusted sub-network, NNI is divided into two types: internal network node interface I-NNI) and external network node interface E-NNI ). I-NNI is the communication interface between the same network or between the network and the trusted network entity control layer, which is used to realize the communication between 0CS in the unified management domain. E-NNI is the control layer bidirectional signaling interface between the network and the external network, the network and the external untrusted network entity control layer communication interface. This usually happens between networks of different carriers. E-NNI interface Signaling will shield the network topology and other information, its transmission of the main information including call control, resource discovery, Connection Control, connection selection and connection routing. Through this interface signaling, ASON can be divided into several subnet management domains, E-NNI can realize the end-to-end connection control between these domains.

2. Interconnection Between ASON and traditional Optical Networks

ASON can communicate with traditional optical networks through UNI and NNI.

2.1 interworking with traditional optical networks through UNI

As shown in the following figure, UNI is used to communicate with the traditional optical network. AS1 and AS2 represent the traditional optical network and the CMS connection management system.

In this mode, the traditional optical network is used as the customer signal access of ASON, and its features are:

A) Make full use of existing network resources.

B) if the traditional optical network is used as the ASON client, the UNI proxy sends the connection request of the network management system to the ASON, And the ASON completes the connection establishment. This model is suitable for the relationship between the existing Man and the new ASON backbone network.

C) the current implementation of the traditional optical network one-way UNI-C, that is, the traditional optical network as the ASON customer.

D. After UNI is used inside the transmission network, UNI cannot be used for users. That is, it does not directly support the customer's soft connection SC) service.

E) Functions with UNI interfaces are only concentrated on data devices and not truly integrated into transmission networks such as SDH devices.

2.2 interworking with traditional optical networks through NNI

As shown in, communication with traditional optical networks through NNI proxy. In this way, the out-of-band distributed ASON is implemented by setting NNI proxy for the traditional optical network.

This method has the following features:

A) traditional optical networks implement NNI functions through NNI proxy. The NNI interface can provide more network information, such as route information and protection and recovery information.

B) NNI interconnection is closer to ASON and has more functions than UNI interconnection. Each NNI proxy can represent one or more node devices.

C) NNI acts as a proxy for one node or network and can provide SC services.

D) For existing networks that cannot be upgraded or transformed, they can be directly interconnected at the transport layer.

E) The management and configuration of ASON and existing networks are the same as that of current multi-vendor interconnection, which cannot achieve unified management and scheduling across the network.

3. ASON and traditional optical network convergence solution