Network basics-Brief description of elements and other knowledge points

Network basics-brief descriptions of elements and other knowledge points I. Network Element data or information networks vary in size or function, but all networks have four common basic elements. 1) Rules or Protocols 2) messages 3) Media 4) device 2. network architecture, Internet architecture the Internet design solves four basic features: 1) fault tolerance capability-a simple definition means that it can continue to execute its normal functions even if some components in the network cannot work. The concept of redundancy is critical to fault tolerance, that is, backup devices or media. 2) scalability-describes the ability of the network to adapt to future changes. Upgrading networks can add new users and devices without the need to redesign the network. 3) Service Quality-display the execution level of the services provided by the network, which refers to the mechanism used to manage network congestion (congestion is caused by the network resources exceeding the network carrying capacity. Because many technologies are integrated (the term "convergence" refers to the concentration of different technologies, such as telephones, videos, and texts, on a single network platform), and different services (groups) on this platform) it can have different priorities. Configuring devices to prioritize different types of data is an example of QoS. Note: priority is generally set based on the sensitivity to time and the importance to users. 4) security involves two aspects: 1. network infrastructure security; 2. Content Security a) Ensure confidentiality: allow only the intended and authorized recipients to read data, and implement B through the Identity Authentication System) maintain communication Integrity: Data Integrity indicates that the information is not changed during transmission from the source address to the destination address. Sender authentication ensures source integrity. The digital signature, hash algorithm, and checksum mechanism can ensure the source and data integrity throughout the network. C) Ensure availability: computer virus attacks and DoS attacks can make the network unavailable. A DoS attack means that an external computer sends a large number of service requests to prevent legitimate users from using network resources. Defense measures are anti-virus software and firewalls (these firewalls are some routers and servers). They create redundant network infrastructures to reduce the single point of failure that can cause network interruptions and reduce the impact of these threats. 3. Two different links and transmission modes 1) circuit switching: Link-oriented network, exclusive, defect: Only one telephone call can occupy all circuits, no other call can use this circuit before the call ends. 2) packet exchange: the unconnected Network Packet Exchange Network is a standard Internet, but the circuit exchange network still has a special market. Today's circuit switching network allows circuit faults and session recovery. The circuit switching network consumes more resources than the packet switching network, but some special consumers need the reliability and security of modern dedicated circuits, for example, a bank's ATM (24-hour independent access ). 4. scalable Internet implementation the Internet is a set of private and common networks connected through routers. Using a layered structure, the high-level network service provides domain name servers that track a large number of Internet addresses. This information is copied and shared with the low-level systems. In this hierarchical structure, most traffic is not directly processed by the upper-layer server. The allocation of such processing work changes the structure of the lower layer. For example, adding a new network service provider (ISP) does not affect the upper layer.