New Broadband Access Network Technology Transformation

There are many ways to access the broadband network. At the same time, these methods also use different access technologies. Each new technology can solve the problem that the old technology cannot implement, here we will introduce the features and principles of these technologies.

Last step

Since June, China Telecom has opened a VPN service for major customers on the newly created CN2, marking the maturity of a new IP bearer network. This bearer network not only adopts the latest technologies such as MPLS, fast convergence, and fast re-routing, but also uses QoS Technology Based on Diffserv mode to divide eight service levels, different broadband access networks are allocated to different businesses of different levels and different queue scheduling mechanisms are used to completely solve the QoS problem on the IP backbone network.

At the same time, the transformation of man is also in full swing. Take Shanghai Telecom as an example. By layered and flat networks, service routers are pushed to the edge, and services are divided by VPLS technology, the QoS problem of man is also effectively guaranteed. However, this does not mean that the IP network's QoS has been solved once and for all. In fact, the most close-to-user broadband access network is the difficulty and focus of IPQoS. "In the future, if a carrier wants to provide more services to home users, QoS at the access layer must be resolved. from the current situation, there is not much problem with carrying only a single data or video business. However, once the business is enriched, especially the integrated business, the access layer will be the biggest weakness of operators." Liu Yongchun, CTO of Shanghai Bell Alcatel, said.

Difficulties

The QoS of the access network has its own special complexity: on the one hand, the bandwidth of the broadband access network is usually restricted and cannot be increased without limit. On the other hand, the bandwidth access network is complex and involves multiple technologies, such as Ethernet, ATM, FR, etc. In addition, it is also a place where multiple services are aggregated, such as video, audio, and data services must be transmitted through broadband access networks.

Zhao Zhuang from the Institute of software technology of the Chinese Emy of Sciences believes that for a long time, the development of QoS for broadband access networks has been restricted for two reasons: "First, people generally think that due to the high convergence of backbone network traffic, the QoS problem of backbone networks is more prominent, it is more difficult to solve, while the QoS problem of the broadband access network is relatively easy to solve. Second, in the past, the broadband access network was generally a single service network, even for multiple service networks, generally, frequency division multiplexing or other Multiplexing technologies are used to isolate different services. In addition, some technologies use point-to-point links to isolate the traffic of different users, and the QoS problem is not prominent." However, during the transformation of operators, multi-service bearer has become a trend. "operators need to define the level before the business enters the network ." He said.

In the past, many QoS mechanisms were proposed to focus on discussing QoS from different network protocol layers. However, few existing solutions systematically combine various QoS mechanisms to solve Network QoS problems. In addition, although there are already a large number of QoS mechanisms, it is difficult to effectively ensure service quality by relying solely on the service quality mechanism, the combination of network capacity planning, service quality mechanism and pricing mechanism is a more practical service quality solution. All of this is the cause of QoS Problems in the broadband access network.

Break questions

For broadband access networks, QoS control points are the key components of access terminals, access platforms, aggregation networks, and BRAS/SR. Because the internal network of the broadband access network is complex and involves multiple technologies, it is a good solution to achieve QoS by adopting the DiffServ idea at this layer, that is, the policies adopt business differentiation and marking, business ing and classification bearer, and Layer 2 802.1D priority processing.

The DiffServ framework is suitable for all networks using the ADSL access mode. There is no essential difference between the ADSL service differentiation method and the IP service differentiation method. It requires scalable, high-capacity, and smart DSLAM to provide IP Forwarding functions, support various QoS mechanisms and user management functions required by DiffServ, and can quickly implement the above processing.

However, the problem lies in another form of broadband access network-Ethernet. At present, most Ethernet switches support some functions required to implement DiffServ, such as classification, labeling, and scheduling. The scheduling module usually implements priority scheduling, weighted cyclic scheduling, and other Scheduling Mechanisms. However, the added features still cannot provide guaranteed Forwarding (AF) and fast forwarding (EF) services over Ethernet based on the DiffServ framework, naturally, differentiated service methods cannot be used to effectively ensure the service quality of multiple businesses. Liu Yongchun believes that the most direct solution is to introduce the home gateway device as soon as possible and identify and classify the service before it enters the carrier's network, thus killing all QoS Problems in the cradle.

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