[Computer Networking] {CMU14-740} Lecture 3: Design Principles

Internetworking with Gateways

We will turn the philosophical and theoretical discussion from last lecture into a practical examination of the TCP/IP architecture. We will examine the various goals of the initial TCP/IP design and look at the famous “End-to-End Argument.”

Lesson Objectives

By the end of this lesson, the student will be able to:

• describe the internet's layered architecture according to the TCP/IP model and argue the importance of architectural features of that model.
• explain the role of the IETF in the internet's operation.
• describe the goals of the TCP/IP design according to Clark88 and identify the fundamental goal.
• explain the ramifications of the robustness, multiple services and multiple networks goals on the design of the TCP/IP protocols.
• explain Saltzer84's “End-to-End” argument. Be able to describe exceptional situations where it may not apply as well as ways in which the modern internet may be moving away from this design philosophy.

Reading

• E2E arguments [Saltzer84]

Slides

• L03_DesignPrinciples.pdf
• L03_DesignPrinciples.pdf (No background version)

Video

• Lecture Video

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RFC 2901

Guide to Administrative Procedures of the Internet Infrastructure

https://tools.ietf.org/html/rfc2901 

 on of the most important concepts of this class

 

 

 

 

TCP/UDP => 

IP => 

bottom => eg. ethernet => direct wire connection between two devices 

 

 

 

 

 

 

 

miss some data => dont wait, fill the gap and go on => delay is a wrong kind of realibility => TCP is not enough (lossing packets is okay) => need a different service

   

 

moving functions to application layers as many as possible => easy to change; simpler code in network and stable network

 TCP will request again if any data lost => inefficient when latency is high

 

 

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作者：车小胖
链接：https://www.zhihu.com/question/53001502/answer/133069062
来源：知乎
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。

3. OSI眼中的TCP/IP

OSI分七层：

七层：应用层

六层：表示层

五层：会话层

四层：传输层

三层：网络层

二层：链路层

一层：物理层

浏览器对应第七、第六、第五层

TCP/IP对应第四、第三层

TCP层对应第四层，即传输层

IP层对应第三层，即网络层

网卡（驱动程序）对应第二层（链路层）、第一层（物理层）

所以 浏览器 + TCP/IP + 网卡（驱动程序）完美对应OSI参考模型七层。

为何要OSI分层？

那是为了让不同的操作系统、不同的厂商的终端设备能够通信，大家遵循一样的协议标准，好比说同一种语言的人可以自由自在地沟通。

分层还可以让不同的底层网卡可以独立实现自己的功能，对下（物理层）实现相同的编码方式，对上（网络层）提供标准的接口，至于内部如何实现，别人并不care。

对于IP层也是，内部独立完成自己的功能，对上提供标准的接口，对下调用标准的接口，这样开发起来非常便利。

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https://www.zhihu.com/question/20583641/answer/104529492 

如何通俗地解释一下 TCP/UDP 协议和 HTTP、FTP、SMTP 等协议之间的区别？

 

 IP => address

TCP => state

UDP => stateless

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