Analysis of mainstream Broadband Access Network Technologies

Broadband access networks are worth learning. So I have studied the technical features and various modes of broadband access networks. I would like to share them with you here and hope they will be useful to you.

Introduction
Communication is one of the fastest growing areas at present. It is an essential tool for people's work and life, and is also one of the basic platforms for current and future economic development. The development of communication networks has gone through the process from narrow band to broadband, from artificial intelligence, from single business to comprehensive business. In the 21st century, the development trend of communication networks in the direction of broadband, personalization, segmentation and integration was more obvious. At present, Internet and mobile communication are the fastest growing technical development and demand.

Broadband Communication Network is an intelligent communication network that features full digitalization, high speed, broadband, and comprehensive business capabilities. A notable feature of the broadband communication network is that it breaks through the speed, capacity, and time space limitations in information data transmission. Broadband communication networks can be divided into two levels: Broadband backbone networks and broadband access networks. This article introduces the development history and status of the communication network technology from two aspects: Broadband backbone network and broadband access network, and discusses the development trend of the broadband communication network.

Broadband Backbone Network Technology
The grouping and switching technologies of the broadband backbone networks that emerged earlier include X.25 and frame relay. After decades of development, the IP technology has become the mainstream broadband network technology, and will develop towards the direction of the ultra-broadband information network with the light Internet technology as the mainstream technology in the future.

Frame Relay
Frame Relay (Frame Relay) is a fast connection-oriented grouping and switching technology. It is a data communication technology developed in the early 1980s S. It evolved from the X.25 group communication technology. Due to the development of transmission technology, the error rate of data transmission is greatly reduced, and the error recovery mechanism of group communication is too cumbersome. Frame Relay simplifies the three-layer protocol of group communication into two layers, that is to say, the second layer of OSI transfers data in a simplified way. Only the functions of the core layer of the physical layer and the link layer are completed, and the network does not perform error correction, re-transmission, and traffic control, and leave these functions to smart terminals for processing. This greatly shortens the processing time and improves the efficiency. However, the biggest problem with frame relay is that there is no relevant regulation on the service quality level and the high service QoS requirements cannot be guaranteed.

Asynchronous Transfer Mode
Asynchronous Transfer Mode (Asynchronous Transfer Mode) [1] is a fast group exchange technology, which is recommended by ITU-T as the information transmission Mode of the B-ISDN of broadband integrated business data network. An ATM organizes information into metadata. The elements contained in the information do not need to appear periodically. This transmission mode is asynchronous.

An ATM cell is a fixed-length group with a total of 53 bytes divided into two parts. The first five bytes are the header, which is mainly used for addressing. The last 48 bytes are information segments used to load information from different users and services. All digital information such as voice, data, and images must be cut, encapsulated into cells in a unified format transmitted in the network, and restored to the desired format at the receiving end. Because the ATM technology simplifies the switching process, removes unnecessary data verification and adopts a fixed cell format that is easy to process, the ATM Switching rate is much higher than that of traditional data networks, such as x.25, DDN, frame Relay.

The ATM network uses some effective service traffic monitoring mechanisms to monitor online user data in real time, minimizing the possibility of network congestion. Assign different priorities to different services, and assign different network resources to services with different priorities. Therefore, ATM provides QoS guarantees for real-time services such as conversational sounds and images. Although ATM has the advantages of fast switching speed, traffic control, service quality assurance, and flexible bandwidth allocation, the overhead and Protocol complexity of ATM make the cost of ATM equipment high, complex maintenance.

Multi-Protocol Label exchange
Multi-Protocol Label Switching MPLS: Multiprotocol Label Switching) [2] is a type of Switching technology between Layer 2 and Layer 3. It introduces a tag-based mechanism to separate routing and forwarding, the label specifies the path of a group through the network, and the data transmission is completed through the label exchange path LSP.

The MPLS network consists of the core part of the label exchange router LSR) and the edge part of the Label Edge Router LER. LSR can be seen as the combination of an ATM switch and a traditional router. It consists of a control unit and a switching unit. LSR is used to analyze IP headers and determine the corresponding transmission level and label switching path LSP ). Because MPLS technology isolates the relationship between the Label Distribution Mechanism and the data stream, its implementation does not depend on the specific data link layer protocol, supports multiple physical and link layer technologies such as IP/ATM, Ethernet, PPP, frame relay, and optical transmission ). MPLS uses the control drive model to initialize the allocation and distribution of tag bundling, and is used to establish the label switching path LSP). It establishes an LSP by connecting several label switching points. One LSP is unidirectional, and two LSPs are required for full-duplex services. MPLS also supports Traffic Engineering and service levels. Because MPLS, combined with traditional IP and ATM technologies, has the advantages of simple implementation, fast switching speed, and service level supporting traffic engineering and business, MPLS has been widely valued.

IP Network Technology
The motivation of IP technology is to achieve interconnection between different network types to share resources and exchange data. IPv4 assigns a 32-bit IP address to the network node to uniquely identify the node. User data is encapsulated in the IP Group. In order to ship the IP Group to the target node by the source node, the IP address uses the routing protocol to create a route from the source node to the destination node. The IP router forwards the route to the destination node by hop according to the destination IP address and the saved route table.

At first, IP technology was mainly used for some simple data services, such as email, file transmission, and remote login. With the successful application of IP technology on the Internet and the rapid development of the Internet, IP is required not only to support simple data services, but also to deliver real-time services such as voice and image. To ensure the QoS of real-time services such as voice and image, we need to improve the traditional best-effort IP technology to provide QoS Assurance. Currently, the IP QoS architecture that provides service quality assurance includes InterServ and DiffServ. InterServ Reserves Resources Based on streams, and DiffServ distinguishes services based on classes for different types of services, different queue scheduling policies are used. DiffServ aggregates business flows at network boundaries and does not need to maintain stream-based status information. Therefore, DiffServ has good scalability and is more suitable for large IP networks than InterServ.

With the growth of the Internet scale and the increasing number of mobile terminal broadband access networks, the disadvantages of IPv4 gradually emerge, including: insufficient address space, no node mobility, poor security, and no QoS guarantee. To solve these problems, IPv6 came into being. IPv6 uses a 128-bit address space and supports node mobility, QoS Assurance, and high security. Therefore, IPv6 may eventually replace IPv4, but in the transition from IPv4 to IPv6, the communication between the two and the resulting security issues need to be solved.

1. Practical application of Broadband Access Network
2. Overview of broadband wireless access technology
3. FTTH leads the revolution in Broadband Access Technology
4. Flexible use of wireless access technology
5. Discussion on the Development Trend of Wireless Network Access Technology