Datacom Novice Must-See Series
Chapter 1 Getting to Know Huawei Datacom (2)
1. What is the OSI Reference Model
2. Why should we study the OSI reference model
3. How do we learn the OSI reference model
1. We need to understand which layers the OSI reference model is divided into
2. How do we understand and remember the 7-layer reference model of OSI
1. Application layer (Application)
4.OSI Reference Model: It is just a reference model.
Do we Xiaobai have a question, why is the OSI model called a reference model?
Two, TCP/IP standard: divided into two types
1. TCP/IP standard model, TCP/IP peer-to-peer model (two major models)
2. TCP/IP peer-to-peer model: what protocol does each layer have
foreword
With the continuous development of Huawei, the technology of data communication is becoming more and more important. Many people have started learning data communication. This article introduces the OSI reference model and the TCP/IP standard.
1. OSI reference model
1. What is the OSI Reference Model
Seven-layer model, also known as OSI (Open System Interconnection). The reference model is a standard system developed by the International Organization for Standardization (ISO) for the interconnection between computers or communication systems , generally known as the OSI reference model or the seven-layer model.
It is a seven-layer, abstract model body, including not only a series of abstract terms or concepts, but also specific protocols.
2. Why should we study the OSI reference model
The OS reference model is an official standard. Understand the OSI reference model, TCP/IP standard model and TCP/IP peer-to-peer model protocol, you are almost clear, for the TCP/IP standard model we will learn below, TCP/IP pair And other standard models, these three models are basically different in layering, and the others are the same.
3. How do we learn the OSI reference model
1. We need to understand which layers the OSI reference model is divided into
The OSI reference model is divided into seven layers , namely the application layer, presentation layer, session layer, transport layer, network layer, data link layer, and physical layer. The following figure has a detailed function introduction.
2. How do we understand and remember the 7-layer reference model of OSI
The preface informs:
We must first remember an English sentence:
all people seem to need data photo (translation: all people seem to need datagram)The initials at the beginning of this sentence represent the letters of the application layer, presentation layer, session layer, transport layer, network layer, data link layer, and physical layer. Next, let us explain them one by one.
1. Application layer ( Application )
Mnemonic: a ll = application layer
Understanding : We understand that the application layer can be represented as some specific applications: such as QQ, WeChat and other software
2. Presentation layer
Mnemonic: p eople = presentation layer
Understanding : The presentation layer indicates how you express it, which is a matter of format, such as mp3, mp4, etc.
3. Session layer ( Session )
Mnemonic: seem = session layer
Understanding : There are three functions, establishment, management, and maintenance. The three functions are embodied in detail: the first thing to do is to establish a session between two devices. When the No. 1 device and No. 2 device are transmitting, the data needs to be maintained, so it needs to be Maintenance (management), when the session ends, you need to remove this link
4. Transport layer ( transport )
Mnemonic: t o = transport layer
Understanding : data segment, representing the protocol TCP/UDP
5. Network layer ( network )
Mnemonic: n eed = network layer
Understanding : data packet, IP address-logical address, what we call packet loss in daily life is IP data packet, which is communication at the network layer, and routers work at this layer.
6. Data link layer ( data link)
Mnemonic: data = data link layer
Understanding : data frame, physical address-MAC address, MAC address is equivalent to the hardware ID card of our device
7. Physical layer ( physical )
Mnemonic: data = data link layer
Understanding : Bit stream is what we know as 0/1,
4.OSI Reference Model: It is just a reference model.
Do we Xiaobai have a question, why is the OSI model called a reference model?
There are three main reasons:
- Too idealistic to be realized;
- It was produced before the network and does not conform to the actual development of the network.
- The division between each layer is too absolute, complicated, and excessive pursuit of perfection .
Two, TCP/IP standard: divided into two types
1. TCP/IP standard model, TCP/IP peer-to-peer model (two major models)
There are two types: 1. TCP/IP standard model 2. TCP/IP peer-to-peer model (Huawei approved standard)
The TCP/IP standard reference model combines the data link layer and physical layer in OSI into the network access layer. This division method is actually contrary to the actual protocol formulation situation, so the TCP/IP standard model and OSI model are integrated The TCP/IP peer-to-peer model is proposed, and the following explanations will also be based on this model.
The internal structure of the 7 layers in the OSI reference model and the four layers of the TCP/IP standard model and the five layers of the TCP/IP peer-to-peer model are the same, but the inclusion of the divided layers is different.
2. TCP/IP peer-to-peer model: what protocol does each layer have
1. Application layer
Protocols: Telnet (to log into our devices), FTP ( to transfer our files ), DHCP ( Dynamic Host Configuration Protocol ), DNS ( Domain Name System ), TFTP ( to transfer files ), SMTP (simple mail transfer protocol) ( Simple Mail Transfer Protocol ) ), SNMP ( to manage our equipment through simple network management ), HTTP ( to manage our equipment, log in to our webpage ) and other protocols .
2. Transport layer
Protocol: reliable TCP (for three-way handshake, four-way handshake) , unreliable UDP (for connectionless) (that is, to transmit data between a and b, I send it if I want, if you lose it, I don't Will resend it to you) (Our qq, WeChat and other software use UDP)
3. Network layer
Protocol: IP (Internetworking Protocol) , ICMP (Internet Control Management Protocol) , IGMP (Internet Master Management Protocol).
4. Data link layer
Protocol: PPPoE (dial-up, a way to surf the Internet) , PPP (the connection method in the wide area network) , Ehternet (Ethernet)
5. Physical layer
It is not what our digital communication engineers want to study, so we will explore here
Third, what is the significance of the existence of the TCP/IP peer-to-peer model and the OSI reference model?
- Data communication needs a standard
- Promote the development of technology
- Faults can be easily located and resolved
- Facilitate communication and promote cooperation
- Easy to manage
- Not conducive to user use.
Summary: Because data communication requires a standard, those standardization organizations have emerged. Standardization organizations formulate unified standards based on the characteristics of our social development or the actual situation.
Summarize
The above is what I want to talk about today. This article only briefly introduces the OSI reference model, the TCP/IP standard model, and the TCP/IP peer-to-peer model (three major models). These three major models must be understood by us, and It is necessary for future work.