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大家可以讨论讨论ISO的七层结构吗?

土豆 2000-10-25 07:45:00
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土豆 2000-12-06
to kagezhao:那SITE命令又是基于什么?

请原谅,我是菜鸟,是在不太懂。
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hu_zy 2000-11-26
physical layer:
The function of the physical layer is to transmit data by defining the electrical specifications between the source and destination. Once it reaches a building, electricity is carried to workstations, servers, and network devices via wires concealed in walls, floors, and ceilings. Data, which can consist of such things as text, pictures, audio, or video, travels through the wires and is represented by the presence of either electrical pulses on copper conducting wires or light pulses in optical fibers.
In this chapter, you will learn about the basic theory of electricity. This will provide a foundation upon which networking at the physical layer of the OSI model can be understood. You will also lean how data is transmitted through physical media, such as cables and connectors. Lastly, you will learn about the different factors that affect data transmission such as, alternating current (AC) power line noise.

Data link layer:
All data sent out on a network is from a source and is going to a destination. After data is transmitted, the data link layer of the OSI model provides access to the networking media and physical transmission across the media, which enables the data to locate its intended destination on a network. In addition, the data link layer handles error notification, network topology, and flow control.
In this chapter, you will learn about LAN media and the IEEE model and you will learn how the data link layer provides reliable transit of data across a physical link by using the Media Access Control (MAC) addresses. In so doing, the data link layer is concerned with physical (as opposed to network, or logical) addressing, network topology, line discipline (how end systems will use the network link), error notification, ordered delivery of frames, and flow control. In addition, you will learn how the data link layer uses the MAC address to define a hardware or data link address in order for multiple stations to share the same medium and still uniquely identify each other.

Network layer:
The network layer is responsible for navigating the data through the network. The function of the network layer is to find the best path through the network. The network layer's addressing scheme is used by devices to determine the destination of data as it moves through the network. In this chapter, you will learn about the router’s use and operations in performing the key internetworking function of the Open System Interconnection (OSI) reference model’s network layer, Layer 3.
In addition, you will learn about IP addressing and the three classes of networks in IP addressing schemes. You also will learn that some IP addresses have been set aside by the American Registry for Internet Numbers (ARIN) and cannot be assigned to any network. Finally, you will learn about subnetworks and subnet masks and their IP addressing schemes.

Transport Layer:
As you know, a router has the ability to make intelligent decisions regarding the best path for delivery of data over a network. This is based on a Layer 3 or network layer addressing scheme. The router uses this information to make forwarding decisions. Once data packets go through the network layer, the transport layer, Layer 4, assumes that it can use the network as a "cloud" to send data packets from the source to the destination. The cloud resolves issues such as "Which of several paths is best for a given route?" In this chapter, you will start to see the role that routers perform in this process. In addition, you will learn how the transport layer regulates the flow of information from source to destination reliably and accurately.
This chapter explains the primary functions that occur at the transport layer. This includes end-to-end control provided by sliding windows and the reliability in sequencing numbers and acknowledgements. In addition, this chapter describes how the transport-layer data stream is a logical connection between the endpoints of a network. Keeping this in mind, you will learn how the transport-layer data stream provides transport services from the host to the destination, often referred to as end-to-end services. In addition, you will learn about TCP and UDP and how they use port numbers to keep track of different conversations that cross the network at the same time, to pass information to the upper layers.

Session Layer:
After data packets provided by the four lower layers travel through the transport layer, they are turned into sessions by the layer 5 protocol or OSI session layer. This is done by implementing various control mechanisms. In this chapter, you will learn about these mechanisms. This includes accounting, conversation control, that is, determining who can talk when, and session parameter negotiation.
The chapter also describes how the session layer coordinates service requests and responses. This occurs when applications communicate between different hosts. You will learn about the processes which occur as data travels through the session layer. Included are, dialogue control and dialogue separation that enable applications to communicate between the source and destination.

Presentation layer:
Now that you have learned about Layer 5 of the OSI model, it is time to look at Layer 6, the presentation layer. This layer is typically a pass-through protocol for information from adjacent layers. It allows communication between applications on diverse computer systems in a manner that's transparent to the applications.
The presentation layer is concerned with the format and representation of data. If necessary, this layer can translate between different data formats. In this chapter, you will learn how the presentation layer provides code formatting and conversion, which is used to make sure that applications have meaningful information to process. Layer 6 is also concerned with the data structures that are used by applications. To better understand this, you will learn how Layer 6 arranges and organizes data before it is transferred.


Application layer:
Now that you have seen what happens to data packets as they travel the presentation layer, its time to look at the last layer in which data packets travel through before reaching their final destination. The last layer or Layer 7 of the OSI model is referred to as the application layer. The application layer is the closest to you as an end-user, when you are interacting with software applications such as sending and receiving e-mail over a network. You will see how the application layer deals with data packets from client-server applications, domain name services, and network applications by examining the following:
Client-Server
Redirectors
Domain Name System
E-mail
Telnet
FTP
HTTP

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hu_zy 2000-11-26
physical layer:
The function of the physical layer is to transmit data by defining the electrical specifications between the source and destination. Once it reaches a building, electricity is carried to workstations, servers, and network devices via wires concealed in walls, floors, and ceilings. Data, which can consist of such things as text, pictures, audio, or video, travels through the wires and is represented by the presence of either electrical pulses on copper conducting wires or light pulses in optical fibers.
In this chapter, you will learn about the basic theory of electricity. This will provide a foundation upon which networking at the physical layer of the OSI model can be understood. You will also lean how data is transmitted through physical media, such as cables and connectors. Lastly, you will learn about the different factors that affect data transmission such as, alternating current (AC) power line noise.

Data link layer:
All data sent out on a network is from a source and is going to a destination. After data is transmitted, the data link layer of the OSI model provides access to the networking media and physical transmission across the media, which enables the data to locate its intended destination on a network. In addition, the data link layer handles error notification, network topology, and flow control.
In this chapter, you will learn about LAN media and the IEEE model and you will learn how the data link layer provides reliable transit of data across a physical link by using the Media Access Control (MAC) addresses. In so doing, the data link layer is concerned with physical (as opposed to network, or logical) addressing, network topology, line discipline (how end systems will use the network link), error notification, ordered delivery of frames, and flow control. In addition, you will learn how the data link layer uses the MAC address to define a hardware or data link address in order for multiple stations to share the same medium and still uniquely identify each other.

Network layer:
The network layer is responsible for navigating the data through the network. The function of the network layer is to find the best path through the network. The network layer's addressing scheme is used by devices to determine the destination of data as it moves through the network. In this chapter, you will learn about the router’s use and operations in performing the key internetworking function of the Open System Interconnection (OSI) reference model’s network layer, Layer 3.
In addition, you will learn about IP addressing and the three classes of networks in IP addressing schemes. You also will learn that some IP addresses have been set aside by the American Registry for Internet Numbers (ARIN) and cannot be assigned to any network. Finally, you will learn about subnetworks and subnet masks and their IP addressing schemes.

Transport Layer:
As you know, a router has the ability to make intelligent decisions regarding the best path for delivery of data over a network. This is based on a Layer 3 or network layer addressing scheme. The router uses this information to make forwarding decisions. Once data packets go through the network layer, the transport layer, Layer 4, assumes that it can use the network as a "cloud" to send data packets from the source to the destination. The cloud resolves issues such as "Which of several paths is best for a given route?" In this chapter, you will start to see the role that routers perform in this process. In addition, you will learn how the transport layer regulates the flow of information from source to destination reliably and accurately.
This chapter explains the primary functions that occur at the transport layer. This includes end-to-end control provided by sliding windows and the reliability in sequencing numbers and acknowledgements. In addition, this chapter describes how the transport-layer data stream is a logical connection between the endpoints of a network. Keeping this in mind, you will learn how the transport-layer data stream provides transport services from the host to the destination, often referred to as end-to-end services. In addition, you will learn about TCP and UDP and how they use port numbers to keep track of different conversations that cross the network at the same time, to pass information to the upper layers.

Session Layer:
After data packets provided by the four lower layers travel through the transport layer, they are turned into sessions by the layer 5 protocol or OSI session layer. This is done by implementing various control mechanisms. In this chapter, you will learn about these mechanisms. This includes accounting, conversation control, that is, determining who can talk when, and session parameter negotiation.
The chapter also describes how the session layer coordinates service requests and responses. This occurs when applications communicate between different hosts. You will learn about the processes which occur as data travels through the session layer. Included are, dialogue control and dialogue separation that enable applications to communicate between the source and destination.

Presentation layer:
Now that you have learned about Layer 5 of the OSI model, it is time to look at Layer 6, the presentation layer. This layer is typically a pass-through protocol for information from adjacent layers. It allows communication between applications on diverse computer systems in a manner that's transparent to the applications.
The presentation layer is concerned with the format and representation of data. If necessary, this layer can translate between different data formats. In this chapter, you will learn how the presentation layer provides code formatting and conversion, which is used to make sure that applications have meaningful information to process. Layer 6 is also concerned with the data structures that are used by applications. To better understand this, you will learn how Layer 6 arranges and organizes data before it is transferred.


Application layer:
Now that you have seen what happens to data packets as they travel the presentation layer, its time to look at the last layer in which data packets travel through before reaching their final destination. The last layer or Layer 7 of the OSI model is referred to as the application layer. The application layer is the closest to you as an end-user, when you are interacting with software applications such as sending and receiving e-mail over a network. You will see how the application layer deals with data packets from client-server applications, domain name services, and network applications by examining the following:
Client-Server
Redirectors
Domain Name System
E-mail
Telnet
FTP
HTTP

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hrbqian 2000-11-26
NDIS 只是一个接口规范,linux 上也有ndis。
强烈建议,讨论 iso/osi 七层在 windows 中如何实现。
特别是链路层、网络层、传输层,会话层。
物理层---网卡
链路层--- nic driver
网络层--- intermediate driver
传输层--- Transport driver
每一层都符合 ndis 接口规范。
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pxq 2000-11-22
怎么没人讨论
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Eeagle 2000-11-19
其实每层都能实现两个功能。
一是对下层协议的支持和管理,二是能被上层协议调用起功能,只有物理层没有下层功能。
具体点就是一个不是最低层也不是最高层的协议,它们能够管理下层,调用下层的功能模块,它的上层也一样能够调用它的功能,且更简单,可能只需要一个函数等(当然不会这么简单),且越到上层功能越多,管理的各层模块越多,调用越简单化,复杂的交给下层,在下层处理。
只所以用这个OSI模型,原因在于使一个复杂的协议变得形象,容易理解,分工具体,易于管理,也容易管理,编程等。
Eeagle
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pxq 2000-11-18
广域网只涉及到ISO/OSI底下三层协议,那么广域网这三层协议与局域网的这三层协议有何区别,中间的通讯如何进行。这几天我看广域网和局域网的这些协议头都大了,希望高手指点指点
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pxq 2000-11-17
怎么没有人讨论!我收回我的发言,
其实TCP/IP协议也包含了ISO/OSI七层协议的内容,只不过是划分的方法不一样,
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kagezhao 2000-11-17
Win下是NDIS接口做的
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kagezhao 2000-11-17
NDIS呀
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Fabio 2000-11-17
TCP/IP协议层分为:
应用层-------就是你的应用程序啦
传输层-------协议包括TCP,UDP,ICMP
网络层-------跑IP协议
数据链路层---包括以太网的协议,还有拨号上网的PPP协议等.

我觉得数据链路层就只是HDLC封装的那一块,但如果把IP包加个PPP或者MP封装,然后才打HDLC包的话,那中间这个PPP/MP又属于哪一层?
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kagezhao 2000-11-17
pxq, u r right
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pxq 2000-11-14
ISO/OSI的七层网络体系结构不是国际标准化组织提出的协议集合.
而互联网网络体系结构是以TCP/IP协议为核心,它是四层的网络结构:通讯子网层.网络层.运输层.运用层.
那么我们讨论七层网络结构有什么用?
有错误,大家别见笑
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borz 2000-11-13
会话层在七层里实际上只是个虚东西,完全可以忽略不计
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kagezhao 2000-11-13
FTP是SITE命令,从文件的第多少个字节开始收取数据(有的服务器不支持,如NT 4.0)
HTTP是请求头中range,也差不多

你看一下 netants 下载时发送的命令就明白了
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土豆 2000-11-11
多谢kagezhao!

我是菜鸟,我不明白HTTP/FTP是怎么实现断点续传的?你可以讲详细细吗?
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kagezhao 2000-11-06
Netants等是用了HTTP/FTP本身实现的功能做断点续传的
即可以指定需要获取文件的哪一部分(HTTP是请求头中range
FTP是SITE命令)这些自然不是传输层的功能
会话层和表示层只是概念,看系统怎么实现了。一般Windows下分4层
应用层,如HTTP,FTP,TELNET,SMTP,POP等
传输层,如TCP等
网络层,如IP等
NDIS层。可以直接访问MAC
至于物理层就不说了
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土豆 2000-11-04
大家会来啊!!!!!!!
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土豆 2000-10-29
怎么没人来,难道嫌分太少了吗?我可以另外在加啊!!!
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土豆 2000-10-26
请问象NetAnts这样支持断点续传功能的下载软件事工作在那一层,在回话层吗?因为在传输层并没有提供断点续传功能啊,自由在回话层才提供了回话的概念。高手指点啦!!!
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