Problems in actual application of ADSL Broadband Access Network

There are many things worth learning about in the ADSL Broadband Access Network. Here we mainly introduce the problems that should be paid attention to in the actual application of the ADSL Broadband Access Network. The ADSL system has strict requirements on the line, and the transmission rate is very sensitive to the transmission distance, line diameter, and copper quality. A considerable number of copper lines built during the Development peaks in the past few years have been built in the rush of time. The full plastic cable has not been closed for acceptance, and has not been inflated for maintenance, cable Joints suffer severe moisture and have low AC/DC performance indicators. In addition, due to factors such as Echo noise and crosstalk between lines, only about 15% of domestic cable lines can be used for ADSL business.

Therefore, we should exercise caution when using ADSL to transmit broadband services on existing telephone cables. ADSL can only be used in areas where the ADSL Broadband Access Network is not yet formed and the cable transmission quality is good. ADSL is only a transitional measure in the early stages of broadband services. Once the penetration rate of broadband services exceeds 10%, it is difficult for ADSL to be competent. If the above expensive transitional measures are widely applied, the opportunities for building fiber networks with high bandwidth will inevitably be lost, forming a new burden, resulting in a waste of investment.

DSLAM Configuration

The DSLAM device configuration is determined based on factors such as user distribution, number of users, cable layout, and coverage area. To ensure the minimum bandwidth, the number of users on each DSLAM node should not be too large. The construction of ADSL Broadband Access networks in various regions should be combined with the construction of local urban optical fiber access networks. In the initial stage of construction, according to the characteristics of ADSL technology, and considering factors such as a small number of user demands and a wide distribution of users, DSLAM should be distributed in a large number of Bureaus, but the capacity of each node should not be too large; before completing the urban ADSL Broadband Access Network, you can install DSLAM in an existing local IDC and use the existing local cable. When the business develops to a certain extent, make DSLAM as close as possible to the user, so as to facilitate the development of users and improve service quality.

Configuration of the Broadband Access Server

In the ADSL Network Architecture, the configuration of Broadband Access Server can be divided into three methods: centralized, distributed, and centralized distributed. Centralized is to set up a broadband access server at the exit of a city's ADSL Broadband Access Network, which is responsible for gathering PPP connections of ADSL users throughout the city and providing the information required for billing such as time length and traffic, and provide dynamic IP addresses for virtual dial-up users. Centralized management has the advantages of Saving Engineering Investment and network operation costs, facilitating management, and facilitating business development. This method is suitable for small cities or medium-sized cities with a small number of DSLAM nodes, a small number of broadband users, and a small business volume at the initial stage of project construction.

Centralized distribution sets up several broadband access servers in a city. Each server is connected to multiple DSLAM nodes in the region, you can partition and process ADSL service connections, billing statistics, and dynamic IP Address allocation across the city. This method is suitable for large and medium-sized cities with a large number of DSLAM nodes. In distributed mode, the Broadband Access Server is installed on the access layer, and the ADSL service connection, billing statistics, dynamic IP Address allocation, and other functions of the node are completed at the DSLAM node. Because the price of broadband access servers is relatively high, it is generally not suitable to be used unless there are many broadband users and the business volume is large, considering the business volume and cost-effectiveness.

ADSL Network Transmission Mode

Currently, there are two main network transmission modes in the ADSL system: Packet transmission mode and ATM Transmission Mode. Because the QoS mechanism of the ATM Transmission Mode can ensure the smooth development of large-capacity real-time video services, most traditional telecom equipment manufacturers still prefer to use the ADSL equipment in the ATM Transmission Mode. In the ADSL system that adopts the Packet transmission mode, the uplink data interfaces of the local DSLAM device and the user data interfaces of the RTU device on the client are currently popular Ethernet interfaces; the Data Transmission Format carried by the ADSL system generally uses Layer 2 Ethernet frames or Layer 3 IP packets with a variable length based on the functional changes of the local terminal and the client device. In the ADSL system that uses the ATM Transmission Mode, the data interface on the uplink of the local DSLAM device is generally a standard ATM interface and can be directly or through a local transmission network connected to the ATM switch; the data transmitted by the ADSL system is in the form of ATM cells, while the RTU device on the user end usually provides the ATM 25.6m interface or 10 M Ethernet interface.

IP address planning

In the development of the Internet, due to the limitations of IPv4, the IP address is very tight. Therefore, in the development of ADSL Broadband Access Network, you should apply for as many public IP addresses as possible. During network planning, you should apply for public IP addresses. You must plan the allocation of public and private IP addresses within the entire network. IP address planning is critical to network scalability and stability. When assigning an IP address, use the class C address as the allocation unit.