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.”
By the end of this lesson, the student will be able to:
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
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。
https://www.zhihu.com/question/20583641/answer/104529492
IP => address
TCP => state
UDP => stateless
[Computer Networking] {CMU14-740} Lecture 3: Design Principles
原文：https://www.cnblogs.com/ecoflex/p/10961873.html