Rapid network development brings challenges to network security and quality of service(QoS). Access control lists (ACLs) are closely related to network security and QoS. By accurately identifying packet flows on a network and working with other technologies, ACLs can control network access behaviors, prevent network attacks, and improve network bandwidth utilization, thereby ensuring network environment security and QoS reliability. This course describes the basic principles and functions of ACLs, types and characteristics of ACLs, basic composition of ACLs, ACL rule ID matching order, usage of wildcards, and ACL configurations.

User management is one of the most basic security management requirements for any network. Authentication, authorization, and accounting (AAA) is a management framework that provides a security mechanism for authorizing some users to access specified resources and recording the operations of these users. AAA is widely used because of its good scalability and easy implementation of centralized management of user information. AAA can be implemented through multiple protocols. In actual applications, the Remote Authentication Dial-In User Service (RADIUS) protocol is the most commonly used to implement AAA. This course describes the basic concepts, implementation, basic configurations, and typical application scenarios of AAA.

With the development of the Internet and the increase of network applications, limited public IPv4 addresses have become the bottleneck of network development. To solve this problem, Network Address Translation (NAT) was introduced. NAT enables hosts on an internal network to access an external network. It not only helps alleviate IPv4 address shortage but also improves the security of the internal network as NAT prevents devices on the external network from directly communicating with hosts on the internal network that uses private addresses. This course describes the motivation behind NAT, and implementations and application scenarios of different types of NAT.

The Internet has become an integral part of our lives, with a wide range of applications such as file transfer, email sending, online video, web browsing, and online gaming. Because of the layered network model, common users can use various services provided by the application layer, without knowing technical details such as communication technology implementations. In previous courses, we have learned technologies related to the data link layer, network layer, and transport layer. This chapter will describe common network services and applications such as FTP, DHCP, and HTTP.

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Wired LANs are expensive and lack mobility. The increasing demand for portability and mobility requires wireless local area network (WLAN) technologies. WLAN is now the most cost-efficient and convenient network access mode. This course introduces the development of WLAN in different phases, concepts related to WLAN technologies, implementation and basic configurations of common WLAN networking architectures, and WLAN development trends.

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As economic globalization and digital transformation accelerate, enterprises keep expanding their scales. More and more branches locate in different regions, with each branch network being considered as a local area network (LAN). The headquarters and branches need to cross geographical locations to communicate with each other. To better carry out services, an enterprise needs to connect these geographically dispersed branches through a wide area network (WAN). The development of the WAN technologies is accompanied by the continuously increased bandwidth.In the early stage, X.25 provided only the bandwidth of 64 kbit/s. Later, the digital data network (DDN) and Frame Relay (FR) increased the bandwidth to 2 Mbit/s. Synchronous digital hierarchy (SDH) and asynchronous transfer mode (ATM) further increased the bandwidth to 10 Gbit/s. Now, the current IP-based WANs provide 10 Gbit/s or even higher bandwidth. This course describes the development history of WAN technologies, especially the implementations and configurations of Point-to-Point Protocol (PPP) and Point-to-Point Protocol over Ethernet (PPPoE).

The ever expanding network and increasing network devices present a significant challenge in managing networks effectively and providing high-quality network services. There are many network management and O&M methods, of which this course describes some of the most common.

In the 1980s, the Internet Engineering Task Force (IETF) released RFC 791 – Internet Protocol, which marks the standardization of IPv4. In the following decades, IPv4 has become one of the most popular protocols. Numerous people have developed various applications based on IPv4 and made various supplements and enhancements to IPv4, enabling the Internet to flourish. However, with the expansion of the Internet and the development of new technologies such as 5G and Internet of Things (IoT), IPv4 faces more and more challenges. It is imperative to replace IPv4 with IPv6. This course describes the reasons for IPv4-to-IPv6 transition and basic IPv6 knowledge.