What Is Systems Network Architecture?

Network architecture refers to the overall design of the communication system, which provides standards for network hardware, software, protocols, access control, and topology. It widely uses the reference model of the Open System Interconnection (OSI-Open System Interconnection) proposed by the International Organization for Standardization (ISO) in 1979.

Computer network involves computer technology, communication, using multiple aspects, complex and orderly. Networks are common in the military, industry, teaching, homes, and corporate groups. There is a strict management order in the management of the network. The computer network system is to connect all computers together through the network to share information, but it has communication defense and interface services. The convenience of computer networks.

Computer networks connect what appears to be a very large world as a whole, but it actually makes the world seem small again. Because through the computer network, people who did nt know it at all might know it. They did nt understand the problem and now they understand it. People can communicate and communicate through computer networks. Science and technology are the primary productive forces. Scientific production technology has promoted the growth of the network. Similarly, the network has also promoted the progress of science and technology. It can be said that they complement each other. The emergence of the Internet has promoted changes in economic methods and society, but it has also put forward stricter requirements for the development of the Internet, and the Internet has continued to develop in the continuous promotion of society. In the modern era of rapid network development, people are gradually accustomed to the use of bank cards and mobile phones, and gradually developed online payment methods. The emergence of software such as Alipay and WeChat has further promoted the progress of the Internet and made people's lives more convenient . Tele-commerce also has good development prospects. ^[1]

1. Network architecture is applicable

In all computer network studies, although there are differences and inapplicability in some specific requirements, they can still meet most of the requirements.

1, network architecture (network architecture): is the level of communication between computers, as well as the set of protocols and interfaces between the layers.

2. Network protocol: It is a set of rules that must be followed when exchanging information between peer entities communicating with each other in computer networks and distribution systems.
3. Syntax: includes data format, encoding, and signal level.
4. Semantics: Includes control information for protocols and error handling.
5. Timing: includes speed matching and sequencing.

Computer network is a very complex system, and there are many problems to be solved and their natures are different. Therefore, in the design of ARPANET, the idea of "layering" was proposed, that is, the large and complicated problems were divided into several smaller and easy to handle local problems.

Layering describes different functions at different levels of a "protocol stack". These protocols define how communication occurs, such as data flow between systems, error detection and correction, data format, data packaging, and other characteristics. The basic structure is shown below.

1. Physical Layer (PhysicalLayer)

Specifies the mechanical, electrical, functional, and procedural characteristics of communications equipment to establish, maintain, and tear down physical link connections. Specifically,

Network architecture

The mechanical characteristics specify the specifications, pin number, and arrangement of the connectors required for network connection; the electrical characteristics specify the signal level on the line, impedance matching, and transmission rate distance limitations when transmitting bit streams over the physical connection Etc .; functional characteristics refer to assigning the exact signal meaning to each signal first, that is, defining the functions of each line between DTE and DCE; procedure characteristics define a set of operating procedures that use signal lines for bit stream transmission, refer to The series of actions of DTE and DCE on each circuit when connection is established, maintained, and information exchanged.

In this layer, the unit of data is called bits. The main equipment of the physical layer: repeater, hub, adapter.

2. Data link layer (DataLinkLayer)

Based on the bitstream service provided by the physical layer, a data link between adjacent nodes is established, and error-free transmission of the data frame (Frame) on the channel is provided through error control, and the action series on each circuit is performed.

The data link layer provides reliable transmission over unreliable physical media. The functions of this layer include: physical address addressing, data framing, flow control, data error detection, and retransmission.

At this layer, the unit of data is called a frame.

Data link layer main equipment: Layer 2 switch, bridge

3.Network layer

Two computers communicating in a computer network may go through many data links or may go through many communication subnets. The task of the network layer is to select the appropriate network routing and switching nodes to ensure timely transmission of data. The network layer combines the frames provided by the data link layer into a data packet. The packet encapsulates the network layer header, which contains the logical address information-the network address of the source and destination site addresses.

If you are talking about an IP address, then you are dealing with layer 3 issues, which are "packet" issues, not layer 2 "frames". IP is part of a Layer 3 problem, and there are routing protocols and Address Resolution Protocols (ARPs). Everything about routing is handled at layer 3. Address resolution and routing are important goals of Layer 3. The network layer can also implement functions such as congestion control and internetworking.

At this layer, the unit of data is called a packet.

Network layer protocols include: IP, IPX, RIP, ARP, RARP, OSPF, etc.

Network layer main equipment: router

4.Transport layer

The data unit of the fourth layer is also called a transport layer that processes information. However, when you talk about specific protocols such as TCP, there are special names. The data units of TCP are called segments and the data units of UDP protocol are called "datagrams". This layer is responsible for obtaining all information, so it must keep track of data unit fragments, out-of-order packets, and other dangers that may occur during transmission. Layer 4 provides end-to-end (end-user to end-user) transparent and reliable data transmission services for the upper layers. The so-called transparent transmission means that during the communication process, the transmission layer shields the upper layers from the specific details of the communication transmission system.

Representatives of transport layer protocols include: TCP, UDP, SPX, etc.

5.Session layer

This layer can also be called the meeting layer or the dialogue layer. In the high level of the conversation layer and above, the unit of data transmission is no longer named separately, collectively called the message. The session layer does not participate in specific transmissions. It provides mechanisms for establishing and maintaining communication between applications, including access verification and session management. For example, the server authenticates the user login by the session layer.

6.Presentation layer

This layer mainly solves the problem of syntax representation of user information. It converts the data to be exchanged from the abstract syntax suitable for a certain user to the transfer syntax suitable for the internal use of the OSI system. That is to provide formatted representation and conversion data services. The compression and decompression of data, encryption and decryption are all handled by the presentation layer. For example, the display of the image format is supported by a protocol located at the presentation layer.

7.Application layer

The application layer provides an interface for operating systems or network applications to access network services.

Representatives of application layer protocols include: Telnet, FTP, HTTP, SNMP, etc. ^[4]