第3章网络体系结构的基本概念

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carried out \ce line pioneer standard, and post spurs\ntrated service months\s, education guide members always everywhere bearing in mind identity, based job post, active play role. To develop differentiated learning education guide party members in accordance with their own situation, target the problems to, based on the work done. Pay attention to the room and room for grass-roots party organizations, grass-roots party organizations have more autonomy in education, making education more ground, full of vitality, good effect. Finally, highlight the normal long-term. o highlight the characteristics of recurrent education, with long flowing, continuous line of perseverance the perseverance to promote educational efforts to realize theparty's ideological and political construction of routine institutionalization. With the party branch as the base unit. Play the role of party branches should be, is the key to educational success. Each branch must take strict education and management responsibility of party members, education based on learning to make specific arrangements, fully mobilize the enthusiasm of party members involved in the education, ensure the Organization in place, measures in place, put in place. To the party organization as the basic form. In the standardized development of learning, make learning more effective efforts, and will adhere to the good party group, organized party, party members and the General Assembly, tell a good party lectures, can drive a good topic about, prevent showy without substance, Sham mules. To implement the education management system for basic support. Democratic mutual evaluation on party members in accordance with the regulations, the real performance criteria and order established, sound carefully dispose of unqualified party members, to further improve the dredge export team, pure self cleaning mechanism. Party leading cadres should adhere to and implement the central group learning system, to which branch of learning exchanges, participation in a dual organization with comrades. Focus on recurrent education, you also need to continue to strengthen the building of grass-roots party organizations. Now, the city also has 88 village party organizations are weak and lax, first Secretary of the village, but conversion requires a process. Recently, the city's party organization focused investigation, check out a total of \here are 640 \ntacted 148 \nd implementation of organizational relationships. Educational management of party members into the Organization, there is a lot of work to do. Weak and lax party continued reorganization as an important task, finish perfect organization, with a good team, Good system. Special highlights of grass-roots party organizations, to be dealt with first in place, further education, reorganization, transformation and educational interaction. In short, through solid and effective work initiatives

第三章网络体系结构的基本概念

教学内容：

3．1 网络通信协议和体系结构的概念

3．2 OSI/RM参考模式 3．3 物理层 3．4 数据链路层 3．5 网络层 3．6 传输层 3．7 运输层

3．8 高层协议教学重点：OSI/RM参考模式

各层的功能

教学难点：各层的功能教学时间： 4学时

roken problem, fill the short Board, so that the majority of party members and fully qualified, comprehensive skills of grass-roots party organizations, grass-roots party level upgrade. Comrades, do a \ng education is of great significance, responsibilities, carry significant implications. City levels party and general members cadres, to deep awareness \n a do\ng education of importance and need, to height of political consciously and full of political enthusiasm, put \n a do\ng education carried out good, for coordination advance \ a full\en-Five\d up construction more high ecological vitality happiness of City provides strong powerful guarantee. Two, starting from the revered Constitution respected the party Constitution was XI Jinping, General Secretary to the party's request, 18 six plenary session of the Central Commission for discipline inspection report \Full strictly administering the party, first of all, to exalt the party Constitution, and pipe the whole party, the ruling party of the party Constitution. Revered Constitution reflected in awe. Party a party of ideals and beliefs purpose, summed up the party's fine tradition and style; a clear party members and what can be done and what must be done, what cannot be done. Each Communist Party Constitution to awe and wary eye enhancing the sacred sense of responsibility and mission. Hearts filled with party Constitution, hold the party line, BA obligations unconditionally carry out party members, according to the Constitution of direction towards standards efforts. Respect reflected in the study the party Constitution means. Some party members joined the party Constitution on the shelf, not to learn, some long-term party according to the Constitution of the party's organization, the party is not required to pay membership dues, loose concept, party organizations of the party organization, and turned a blind eye on the tasks assigned by the Organization, were forgotten, forgotten vows performance the party Constitution. Constitution is the fundamental standard of our Communists are slim, the party Constitution to repeatedly learn, practice, thinking, learning and thinking, thinking and row, rowever-spiraling increase in the learning process. Respect party lines reflected in practice. Two to learn a basic Constitution Party rules, series of speeches, the key to be qualified party members. To be qualified party members, standards are not high, but if he does take a ruler of the party Constitution to \not easy. Carry out study and education, every party must control the party's eight obligations, ask, look for gaps, identify problems, clear direction, work to solve specific problems. Actively practicing in the production life of the eight obligations, to play a vanguard and exemplary role, truly a party banner. \organizations carried out \ce line pioneer standard, and post spurs\oncentrated service months\s, education guide members always everywhere bearing in mind identity, based job post, active play role. To develop differentiated learning education guide party members in accordance with their own situation, target the problems to, based on the work done. Pay attention to the room and room for grass-roots party organizations, grass-roots party organizations have more autonomy in education, making education more ground, full of vitality, good effect. Finally, highlight the normal long-term. o highlight the characteristics of recurrent education, with long flowing, continuous line of perseverance the perseverance to promote educational efforts to realize theparty's ideological and political construction of routine institutionalization. With the party branch as the base unit. Play the role of party branches should be, is the key to educational success. Each branch must take strict education and management responsibility of party members, education based on learning to make specific arrangements, fully mobilize the enthusiasm of party members involved in the education, ensure the Organization in place, measures in place, put in place. To the party organization as the basic form. In the standardized development of learning, make learning more effective efforts, and will adhere to the good party group, organized party, party members and the General Assembly, tell a good party lectures, can drive a good topic about, prevent showy without substance, Sham mules. To implement the education management system for basic support. Democratic mutual evaluation on party members in accordance with the regulatons, the real performance criteria and order established, sound carefully dispose of unqualified party members, to further improve the dredge export team, pure self cleaning mechanism. Party leading cadres should adhere to and implement the central group learning system, to which branch of learning exchanges, participation in a dual organization with comrades. Focus on recurrent education, you also need to continue to strengthen the building of grass-roots party organizations. Now, the city also has 88 village party organizations are weak and lax, first Secretary of the village, but conversion requires a process. Recently, the city's party organization focused investigation, check out a total of \here are 640 \d 148 \nd implementation of organizational relationships. Educational management of party members into the Organization, there is a lot of work to do. Weak and lax party continued reorganization as an important task, finish perfect organization, with a good team, Good system. Special highlights of grass-roots party organizations, to be dealt with first in place, further education, reorganization, transformation and educational interaction. In short, through solid and effective work initiative课程性质：计算机网络技术基础学科。

基本理念：网络技术主要是以硬件和协议分析，以及相关的通

信技术，网络互连和数据安全等各个方面的学习。

教学思路：是以通信基础知识为主，为学生补充计算机网络所

需要的部分通信方面的基础知识，主要是以概念、功能和方式的介绍为主。

内容目标：本章是要通过学习，使学生了解服务器设备选择的

要求和特点，以及设备的安装。

实践分析：通过网络体系结构的学习，了解网络各层的功能和

实现，以及他们的区别。

问题思考：对一些重要的内容，对学生启发教学，并提出问题，

使他们能够自己思考了解、理解。

具体问题：1、网络通信协议的功能。 2、什么是OSI/RM？

3、计算机网络被划分成几层，各层的功能是什么？

from the revered Constitution respected the party Constitution was XI Jinping, General Secretary to the party's request, 18 six plenary session of the Central Commission for discipline inspection report \Full strictly administering the party, first of all, to exalt the party Constitution, and pipe the whole party, the ruling party of the party Constitution. Revered Constitution reflected in awe. Party a party of ideals and beliefs purpose, summed up the party's fine tradition and style; a clear party members and what can be done and what must be done, what cannot be done. Each Communist Party Constitution to awe and wary eye enhancing the sacred sense of responsibility and mission. Hearts filled with party Constitution, hold the party line, BA obligations unconditionally carry out party members, according to the Constitution of direction towards standards efforts. Respect reflected in the study the party Constitution means. Some party members joined the party Constitution on the shelf, not to learn, some long-term party according to the Constitution of the party's organization, the party is not required to pay membership dues, loose concept, party organizations of the party organization, and turned a blind eye on the tasks assigned by the Organization, were forgotten, forgotten vows performance the party Constitution. Constitution is the fundamental standard of our Communists are slim, the party Constitution to repeatedly learn, practice, thinking, learning and thinking, thinking and row, rowever-spiraling increase in the learning process. Respect party lines reflected in practice. Two to learn a basic Constitution Party rules, series of speeches, the key to be qualified party members. To be qualified party members, standards are not high, but if he does take a ruler of the party Constitution to \not easy. Carry out study and education, every party must control the party's eight obligations, ask, look for gaps, identify problems, clear direction, work to solve specific problems. Actively practicing in the production life of the eight obligations, to play a vanguard and exemplary role, truly a party banner. \organizations2

carried out \ce line pioneer standard, and post spurs\ntrated service months\s, education guide members always everywhere bearing in mind identity, based job post, active play role. To develop differentiated learning education guide party members in accordance with their own situation, target the problems to, based on the work done. Pay attention to the room and room for grass-roots party organizations, grass-roots party organizations have more autonomy in education, making education more ground, full of vitality, good effect. Finally, highlight the normal long-term. o highlight the characteristics of recurrent education, with long flowing, continuous line of perseverance the perseverance to promote educational efforts to realize theparty's ideological and political construction of routine institutionalization. With the party branch as the base unit. Play the role of party branches should be, is the key to educational success. Each branch must take strict education and management responsibility of party members, education based on learning to make specific arrangements, fully mobilize the enthusiasm of party members involved in the education, ensure the Organization in place, measures in place, put in place. To the party organization as the basic form. In the standardized development of learning, make learning more effective efforts, and will adhere to the good party group, organized party, party members and the General Assembly, tell a good party lectures, can drive a good topic about, prevent showy without substance, Sham mules. To implement the education management system for basic support. Democratic mutual evaluation on party members in accordance with the regulations, the real performance criteria and order established, sound carefully dispose of unqualified party members, to further improve the dredge export team, pure self cleaning mechanism. Party leading cadres should adhere to and implement the central group learning system, to which branch of learning exchanges, participation in a dual organization with comrades. Focus on recurrent education, you also need to continue to strengthen the building of grass-roots party organizations. Now, the city also has 88 village party organizations are weak and lax, first Secretary of the village, but conversion requires a process. Recently, the city's party organization focused investigation, check out a total of \here are 640 \party members are not contacted 148 \nd implementation of organizational relationships. Educational management of party members into the Organization, there is a lot of work to do. Weak and lax party continued reorganization as an important task, finish perfect organization, with a good team, Good system. Special highlights of grass-roots party organizations, to be dealt with first in place, further education, reorganization, transformation and educational interaction. In short, through solid and effective work initiative第三章网络体系结构的基本概念

第一节协议和体系结构

一、网络通信协议(Protocol)

数据链路是由物理链路和逻辑链路组成的。其中，逻辑链路就是由协议和相应的规程组成的。 1．协议的定义

也称为网络协议。网络通信中要完成的包括：信息表示、对话控制、顺序控制、路由选择、链路管理、差错控制、信号传送与接收等问题,这些都是可以通过相关的协议来实现的。

定义：为网络数据通信而制定的规则称之为网络协议。

网络协议3个要素：语法、语义和同步（时序）。

(1)语法：数据和控制信息的结构和格式。【目的地址，源地址，以及相应的位置】

(2)语义：控制信息的含义。

【何种控制信息需要发出，响应如何】

(3)同步：即通信中事件的实现顺序。【举例：说话的过程，来说明问题。】 2．网络协议的层次结构

计算机网络需要实现的任务是复杂的，所以协议也必

然会是很复杂。要单独通过一个模块实现是很复杂的，实

carried out \ce line pioneer standard, and post spurs\oncentrated service months\s, education guide members always everywhere bearing in mind identity, based job post, active play role. To develop differentiated learning education guide party members in accordance with their own situation, target the problems to, based on the work done. Pay attention to the room and room for grass-roots party organizations, grass-roots party organizations have more autonomy in education, making education more ground, full of vitality, good effect. Finally, highlight the normal long-term. o highlight the characteristics of recurrent education, with long flowing, continuous line of perseverance the perseverance to promote educational efforts to realize theparty's ideological and political construction of routine institutionalization. With the party branch as the base unit. Play the role of party branches should be, is the key to educational success. Each branch must take strict education and management responsibility of party members, education based on learning to make specific arrangements, fully mobilize the enthusiasm of party members involved in the education, ensure the Organization in place, measures in place, put in place. To the party organization as the basic form. In the standardized development of learning, make learning more effective efforts, and will adhere to the good party group, organized party, party members and the General Assembly, tell a good party lectures, can drive a good topic about, prevent showy without substance, Sham mules. To implement the education management system for basic support. Democratic mutual evaluation on party members in accordance with the regulatons, the real performance criteria and order established, sound carefully dispose of unqualified party members, to further improve the dredge export team, pure self cleaning mechanism. Party leading cadres should adhere to and implement the central group learning system, to which branch of learning exchanges, participation in a dual organization with comrades. Focus on recurrent education, you also need to continue to strengthen the building of grass-roots party organizations. Now, the city also has 88 village party organizations are weak and lax, first Secretary of the village, but conversion requires a process. Recently, the city's party organization focused investigation, check out a total of \here are 640 \d 148 \nd implementation of organizational relationships. Educational management of party members into the Organization, there is a lot of work to do. Weak and lax party continued reorganization as an important task, finish perfect organization, with a good team, Good system. Special highlights of grass-roots party organizations, to be dealt with first in place, further education, reorganization, transformation and educational interaction. In short, through solid and effective work initiative现和更新都不方便，所以采用层次结构模型来描述网络协议。每一层定义了一个或多个协议，以完成相应的部分的通讯功能。

【举实际中的例子来说明，公司的层次；邮局的例子】 (1)分层的概念。

体现了“分工合作”的思想。每一层只需要关心自己

所需要做的工作。

这种结构化的设计方法，各层次相对独立、界限分明，

以便网络的硬件和软件分别去实现。 (2)服务的概念。

下层向上层提供“服务”，上层使用下层的“服务”，

同时又为更高一层提供自己的“服务”。

【区别：协议是水平的关系，服务是垂直的关系】 (3)接口的概念。

接口是相邻层间交换信息的连接点。低层向高层通过

接口提供服务。

【就像是电视的遥控器，只要使用就可以了，不用了

解内部的功能构造】 (4)对等实体的概念。

每一层次中包括两个实体，称为对等实体。 (5)通信协议的概念。

网络中各层的对等实体之间都将进行通信，需要有一套双方都遵守的规则──通信协议。

carried out \ce line pioneer standard, and post spurs\ntrated service months\s, education guide members always everywhere bearing in mind identity, based job post, active play role. To develop differentiated learning education guide party members in accordance with their own situation, target the problems to, based on the work done. Pay attention to the room and room for grass-roots party organizations, grass-roots party organizations have more autonomy in education, making education more ground, full of vitality, good effect. Finally, highlight the normal long-term. o highlight the characteristics of recurrent education, with long flowing, continuous line of perseverance the perseverance to promote educational efforts to realize theparty's ideological and political construction of routine institutionalization. With the party branch as the base unit. Play the role of party branches should be, is the key to educational success. Each branch must take strict education and management responsibility of party members, education based on learning to make specific arrangements, fully mobilize the enthusiasm of party members involved in the education, ensure the Organization in place, measures in place, put in place. To the party organization as the basic form. In the standardized development of learning, make learning more effective efforts, and will adhere to the good party group, organized party, party members and the General Assembly, tell a good party lectures, can drive a good topic about, prevent showy without substance, Sham mules. To implement the education management system for basic support. Democratic mutual evaluation on party members in accordance with the regulations, the real performance criteria and order established, sound carefully dispose of unqualified party members, to further improve the dredge export team, pure self cleaning mechanism. Party leading cadres should adhere to and implement the central group learning system, to which branch of learning exchanges, participation in a dual organization with comrades. Focus on recurrent education, you also need to continue to strengthen the building of grass-roots party organizations. Now, the city also has 88 village party organizations are weak and lax, first Secretary of the village, but conversion requires a process. Recently, the city's party organization focused investigation, check out a total of \here are 640 \party members are not contacted 148 \nd implementation of organizational relationships. Educational management of party members into the Organization, there is a lot of work to do. Weak and lax party continued reorganization as an important task, finish perfect organization, with a good team, Good system. Special highlights of grass-roots party organizations, to be dealt with first in place, further education, reorganization, transformation and educational interaction. In short, through solid and effective work initiative (6)层次结构的概念。

二、网络体系结构

1．网络体系结构的定义

定义：计算机网络的所有功能层次，各层次的通信协

议以及相邻层次间接口的所有集合。 2．网络体系结构的分层原则

网络协议都采用层次结构。不同网络协议的分层方法

会有很大差异。分层考虑原则：

(1)各层功能明确。具有自己特定的，与其他层次不

同的基本功能。

(2)接口清晰简洁。要求通过接口的信息量最小。 (3)层次数量适中。避免层次太多而引起系统和协议

复杂化。

(4)强调标准化。各层功能的划分和设计应强调协议

的标准化。