pushed by timeemmm~~入csIt's a little late1年,Only then did I realize that I still didn’t have a good grasp of this year and only did a good job in the class,远远不够,There's no way but to catch up now.Listen to my brother's suggestion to enter the pit小林coding,The following article also refers to this article.Really super dry love,Just organize your notes here.emmmI didn't study well in the online semester,It is reasonable to brush the kingly way,My mediocrity was skipped to the Department of Algorithms and Computing2The experiment was tortured to the point of exhaustionhhhh.Pick it up now,the back,By the way, let me sort out some small problems for self-review..

目录

TCP/IP网络模型

应用层

传输层

TCP传输控制协议（Transmission Control Protocol）

UDP

网络层

 IP 协议（Internet Protocol）

寻址——Distinguishing equipment：IP地址

路由

 网络接口层（Link Layer）

以太网

TCP/IP网络模型

In-class and postgraduate examinations seem to be combined with realityTCP/IPThe model and the seven-layer model are summed up5层模型,Here's a closer look at the actual4layer model.Top down as follows：（Layer）【can be collectively referred to as data packets】

应用层

应用软件（HTTP【消息或报文（message）】、FTP、Telnet、DNS、SMTP）,During communication, the data packet will be downloaded to the transport layer（Provide network services for the application layer）.Transmission is none of his business.用户态（Others are kernel state）.

传输层

传输协议：TCP、UDP.

TCP传输控制协议（Transmission Control Protocol）

Most applications such asHTTP应用层协议.

比UDP优点：流量控制、超时重传、拥塞控制——Ensure that data packets can be reliably transmitted to the other party.

UDP

simply send packets,不保证抵达,实时性好,传输效率高.To achieve reliable transmission, it is necessary toTCPFeatures are implemented at the application layer,Commercialization is not easy.

The data that the application needs to transfer is too large（超过MSS——TCP最大报文段长度）direct transmission is not easy to control=>数据包分块（Just resend chunks when corrupted）：【TCP段（TCP Segment）】.

区分应用：端口（The transport layer message with you）.通常Web:80,远程登录服务器：22.Each tab of the browser client is an independent process,Operating system assigns ephemeral port numbers.

网络层

The specific transmission between devices is not the responsibility of the transport layer,The actual network is complex,involves path and node selection,These are controlled by the application layer.

 IP 协议（Internet Protocol）

The message of the transport layer is its data part,加上IP报头=>IP报文,其大小超过MTU（Ethernet is usually1500字节）

just shard.The protocol includes addressing（导航）和路由（steering wheel）.【包（packet）】

  图片转载自小林coding

寻址——Distinguishing equipment：IP地址

IPv4:32位,网络号（子网）,主机号（Host under subnet）.子网掩码计算（&）.广播地址.in netmask“位格式”也被称为CIRD格式（CIDR=无类别域间路由选择）.

路由

The network device has a gateway、路由器、交换机等,需要路由算法.The packet needs to be forwarded to the corresponding subnet.

 网络接口层（Link Layer）

This is the same as the abstract in class5层协议不同,But his name is easier to understand,After all, in the network.再加MAC头部=>数据帧（Data frame）.

以太网

组成部分：such as computer ethernet interface、Wi-Fi接口、以太网交换机、router thousand/万兆以太网口、网线等.

在局域网内,Technology that connects nearby devices to enable them to communicate.它不用IP而是MAC地址,at the link level,工作在网卡.

 图片转载自小林coding

问题整理：

1. TCP/IP网络模型？Packet form and encapsulation process of each layer？those layers are userland？those layers are kernel state？
2. In which layer is the application software implemented?？
3. List several application layer protocols（应用功能）.
4. Does the application layer care about how data is transmitted?？
5. Which layer provides network services for the application layer？
6. The transport layer has several transport protocols？Which application is used more？举例.各自优点？
7. UDPIs reliable transmission possible?？展开.
8. Can the data at the application layer be too large for direct transmission?？为什么？MSS是什么？
9. How to send and receive data to distinguish applications？
10. Web、远程登录服务器、The browser client port number？How the port number is told to the receiver？
11. The transport layer is responsible for the transmission between specific devices, right?？为什么？
12. The most commonly used protocols at the network layer？其组成？
13. Chunking and Sharding？
14. MTU？how big is usually？
15. 如何区分设备？详细说明.
16. What is the subnet mask and broadcast address？
17. CIDR是什么？详细说明.
18. example network device.
19. Network interface layer to encapsulate data？
20. 以太网是什么？Its means of identification equipment？What level do you work at？