TMN-Based Access Network Management

There are many areas worth learning about access network management. Here we mainly introduce the TMN-based access network management. Digitalization, broadband and intelligence of access networks are becoming an important task for the development and construction of communication networks. Network management is an important aspect of communication network construction. To ensure normal, reliable, economic, and secure operation of the access network, it is necessary to establish an access network management system.

Access Network Overview

Access Network (AN) refers to the physical Network that implements the transfer carrying function between the user's Network interface UNI) and the Business node interface SNI. The goal is to establish a standardized interface method, with a monitored access network, users can obtain comprehensive services such as voice, data multimedia, and cable TV. With the advent of the era of communication and computer integration, the digitalization, broadband and intelligence of access networks have become one of the future directions of communication technology development.

Various access network technologies and products launched in recent years can be classified into the following three types: the first type is to use the new digital silent demodulation technology on the original copper cable to Increase the rate, xDSL technology, such as HDSL, ADSL, and VADSL, has the advantage of fully utilizing existing copper resources. Its disadvantage is that the bandwidth is small and the transmission rate and distance are mutually restricted. The second type is access networks based on optical fibers, such as SDH and active optical networks connected to AON), passive optical networks connected to PON), and HFCs and interchangeable digital images connected to SDV, among them, the main application is the most extensive, the advantage is that the bandwidth is large, but the cost is high. The third type is wireless access technologies, such as microwave access, satellite communication, and fixed wireless access to FWA. These technologies are currently not widely used. In practical applications, these access technologies are often used together to form a complete access network system together with the network management system.

The V interface is a standard interface between the local device and the vswitch of the access network. V interfaces include V1, V2, V3, V4, V5, and VB. V1 and V3 correspond to the basic rate of ISDN (2B + D) and the basic group rate of 30B + D) respectively. The difference between V2 and V4 is that V2 can be reused. The V5 interface can be divided into V5.1 and V5.2 based on the speed. V5.1 consists of a 2048kb/s link, while V5.2 supports a maximum of 16 2048kb/s links. The access network corresponding to V5.1 does not have the set line function, and the access network corresponding to V5.2 has the set line function. V5.1 supports general telephone users (PSTN), basic ISDN speed access 2B + D), and leased line services. In addition to all services of V5.1, V5.2 also supports services with an ISDN base group speed of 30B + D. The VB interface is the interface between the Broadband Access Network and the broadband service node. the broadband service node is based on ATM, and the broadband access network is mostly based on optical fiber and microwave. Currently, VB interface standards are still being developed.

ITU has successively proposed a series of access network technical standards, such as G.964V5.1 interface and G.965V5.2 interface. These standards play an extremely important role in the development and application of access network technology. With the development requirements of broadband access network, ITU is developing and improving VB5.1, VB5.2 broadband interface G.967), B-ISDN UNI interface I .432) and broadband access G.966) and other suggestions, these standards and suggestions will play an important role in the future development of access network technology.

Access Network Management System

The Network Management of the access network should be included in the Telecom Management Network TMN. The telecom management network consists of BML (management layer), SML (business management layer), NML (network management layer), EML (Network Element Management Layer), and EL (Network Element Layer. Each management layer provides five management functions: performance management, configuration management, security management, fault management, and billing management. Different layers have different management functions. The Network Management System of the access network can be viewed as the Network Element Management in TMN, and is connected to TMN through the standard interface Q3.

ITU-T put forward the program-controlled switch and access network combined with open digital interface, that is, V5 interface. The access network should eventually be connected to the telecom management network through the Q interface. The management of access networks by China Telecom Management Network is essentially the management of V5 interfaces. It also includes configuration management, fault management, performance management, and security management. After the V5 interface is introduced, the access network becomes an open system, and devices can be produced by different manufacturers. Because access network devices of different standards have different management systems and are difficult to interwork with each other and cannot share management data and information, a unified nationwide access network management system must be established, centralized monitoring, maintenance, and management of the access network are implemented, and the access network management system exchanges management information with other specialized network management systems through standard interfaces and is incorporated into TMN.

The current network management is to divide the entire telecommunication network into different private networks for management, that is, management by access network, signaling network, exchange network and transmission network respectively. This also requires the development of an integrated network management monitoring system to interconnect various network management systems. According to the functional model of the Telecom Management Network, the integrated network management and monitoring system belongs to the network layer. On this basis, the business layer is constructed, the access network management is incorporated into the Telecom Management Network, and finally the Transaction Layer of the Telecom Management Network is constructed, gradually transitioned to the telecom management network.

Key Technologies

Network management of access networks is an important part of ensuring efficient, reliable, and secure operation of access networks. During the construction of the access network, an access network management system should be established simultaneously to meet the maintenance and management needs of the access network. Meanwhile, the interconnection between the access network management and the primary network management should be accelerated. The Network Management of an access network consists of the following three aspects:

1) general network management: mainly refers to access network configuration management and performance management, including management of various types of interfaces and Management of transfer part. Configuration Management is closely related to the management of corresponding business nodes. For example, for an access network used in PSTN, the network management of the access network and the local exchange network must work together to complete configuration management.

2) centralized equipment maintenance: It mainly refers to fault management of various devices used in the access network to ensure the integrity of equipment usage, especially for the management of remote small-capacity devices, including power supply and environment ). To ensure the rational use of various resources, this function should be centrally maintained in a large scope.

3) support for business quality assurance: mainly through the interconnection with other business management systems, to provide support for business quality assurance. The business network management systems that need to be interconnected with the access network management are: 112 the centralized acceptance system, the line number management system, and the business processing front-end system are related to dedicated services that can be reconfigured ), A service network management system that uses an access network as a bridge. Access Network Management also involves some key technologies to ensure the smooth development of access network management. These key technologies mainly include the following two types:

1) supports standard management interface technology in multi-vendor equipment environments, including standard management interface technology and standard management interface testing technology. The introduction of the V5 interface makes the access network an open system, and a large number of equipment manufacturers are emerging, forming a multi-vendor device environment for business networks and access networks. It is one of the key technologies that must be addressed by the network management system of access networks to centrally manage multiple devices of multiple manufacturers for interconnection, these are bound to put forward higher requirements on the management of access network management interfaces.

2) network management architecture technology that supports the Sustainable Construction of the access network management system. The access network is constantly developing, and new technologies are emerging. The Network Management System of the access network must be constantly updated to adapt to the development of the technology, which puts forward higher requirements on the network management architecture of the access network.

TMN-Based Access Network Management

Network Management of the access network has multiple forms, of which TMN-based network management is the main development trend. The SMF in the access network coordinates the operation between UPF, CF, TF and SPF, and provides the management interface Qan for the network management system. Access Network Management is divided into two entities: Management Function Structure and extraordinary management function structure, such as WSF of workstation function and OAF of adapter function. There are three management function entities:

1) PCF-OSF port/core management functions-operating system functions): the access network function structure of UPF, SPF and CF management. Its basic management function is to manage SNI, UNI and Its supported services, including SNI configuration, UNI configuration, UPF/SPF/CF failure and performance management. When UNI uses the V interface, the PCF-OSF manages the V5 interface and its supported businesses.

2) TF-OSF transfer management function OSF) Management TF entity, its basic function is to configure TF and performance and fault management. TF specific equipment and technology such as xDSL, ATM, HFCs) resulting in different TF-OSF functions.

3) The functional entity on PCF-OSF and TF-OSF is the CO-OSF scheduling management function OSF ). Because the PCF-OSF and TF-OSF are relatively independent, and closely related with the specific access technology, the upper CO-OSF needs to coordinate and schedule from the perspective of the whole network access network, in particular, it handles faults and performance management related to the entire network.

Compared with the function structure of the EM-OSF, we can see that SMF is actually used to manage UPF, CF, TF and SPF through the OX interface. In October 1997, The ITU-T 4th research group decided to delete the QX interface and intermediary MD provisions from the current TMN structure, while reserving room for inserting new interfaces and supporting functional modules, therefore, the implementation methods of this interface vary greatly from vendor to vendor. interfaces such as Q3 and OC are usually used. When medium and small capacity devices in the OC interface access network cannot provide interfaces Q3, the interfaces provided by these interfaces are named QX. Like interfaces Q1 and Q2, management objects are defined in the traffic-oriented manner, the communication protocol stack is short-stack, which is not suitable for centralized network management of large-capacity devices. The Q3 interface is an object-oriented full-stack protocol that supports layer-7 network management and has comprehensive management functions, so ITU-T is recommended to use Q3 interface. However, the full stack feature of the Q3 interface makes it difficult to implement it. At present, this interface is mainly determined by the number of trade-offs of each vendor on the Q3 interface standard and the future development direction of its products.

For the Qan interface, the main goal of TMN is to solve the compatibility of devices of different vendors and the smooth scalability of application systems at different device levels, network levels, and operation levels, fundamentally, Advanced Interface technologies are required, for example, the syntax, semantics, and operation of interfaces must be separated from the semantic descriptions of interfaces of devices. Inheritance and encapsulation technologies are supported. The object-oriented feature of the Q3 interface is just the choice of Qan. Therefore, all vendors use the Q3 interface or work in this direction.