概念辨析
URL:A Uniform Resource Locator (URL), colloquially termed a web address,[1] is a reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it.
- URL不仅说明资源位置，也说明获取方式
- URL是www发明人Berners-Lee1994年定义-RFC1738
- URL和Http协议是构成www的基石
HTTP:HTTP协议的制定起源于WWW的发明，目的是为网际内容的传输提供统一的标准
HyperText:即超文本，通过链接（Hyperlink）引用其他文本或文本相关的元素的一种网状文本
几种开放源码的TCP/IP协议栈比较
TCP/IP、Http、Socket的区别
简述TCP连接的建立与释放（三次握手、四次挥手）TCP是面向连接的运输层协议，它提供可靠交付的、全双工的、面向字节流的点对点服务。HTTP协议便是基于TCP协议实现的。（虽然作为应用层协议，HTTP协议并没有明确要求必须使用TCP协议作为运输层协议，但是因为HTTP协议对可靠性的的要求，默认HTTP是基于TCP协议的。若是使用UDP这种不可靠的、尽最大努力交付的运输层协议来实现HTTP的话，那么TCP协议的流量控制、可靠性保障机制等等功能就必须全部放到应用层来实现）而相比网络层更进一步，运输层着眼于应用进程间的通信，而不是网络层的主机间的通讯。我们常见的端口、套接字等概念就是由此而生。（端口代表主机上的一个应用进程、而套接字则是ip地址与端口号的合体，可以在网络范围内唯一确定一个应用进程） TCP协议的可靠传输是通过滑动窗口的方法实现的；拥塞控制则有着慢开始和拥塞避免、快重传和快恢复、RED随机早期检测几种办法。
Internet和WWW的区别：The World Wide Web is a collection of web pages following the http protocol that can be accessed via the Internet from any part of the world.
HTTP的请求方法OPTIONS
WebSocket:通过单个Tcp连接的全双工通信通道
The WebSocket protocol was standardized by the IETF as RFC 6455 in 2011, and the WebSocket API in Web IDL is being standardized by the W3C.
WebSocket is a different protocol from HTTP. Both protocols are located at layer 7 in theOSI model and, as such, depend on TCP at layer 4.
Websocket和HTTP协议都位于应用层，基于
OSI思想：Its goal is the interoperability of diverse communication systems with standard protocols通过标准化的协议实现不同的通信系统间的互操作性
层与层之间的关系：A layer serves the layer above it and is served by the layer below it.
OSI工程有ISO组织发起
Apache JServ Protocol：一个二进制协议
Binary protocol
常见协议
Telnet协议
图解Window下Telnet与远程桌面登陆工具使用
Telnet协议：应用层协议，windows上的telnet服务即telnet协议的实现
Telnet服务与Romote Desktop的区别：Remote desktop 实现的是微软开发的RDP协议
- Telnet is an unencrypted text-only connection to a remote computer’s command shell. SSH or Secure SHell is the encrypted cousin to Telnet and is quickly replacing it for remote command shell access. Telnet/SSH are typically used for UNIX-based systems and devices like routers and sometimes printers.
- Remote Desktop is an encrypted connection to a Windows machine that allows you to run the full Windows interface remotely. It is literally like being logged in to the remote computer. Your keystrokes and mouse movements are sent to it, and it returns the appropriate graphics, sounds, even print jobs if you do it right.
- Other platforms have slightly similar technologies, such as X-Windows and VNC. The other cool thing about Remote Desktop is a company (or ambitious individual) can set up a single computer as what’s called a Terminal Server and serve up remote desktops to dozens or even hundreds of users at the same time. This greatly simplifies life since they now essentially only have to maintain the applications and such on one computer or farm of computers. Many retail point-of-sale and call center environments work this way. All the ‘end user’ needs is a very basic device that can make and display the RDP (Remote Desktop Protocol) connection. Here, I use Linux-based ones that cost under $200 and require no maintenance. These are known as ‘thin clients’ and usually have no moving parts at all. You can also convert otherwise-obsolete PC’s to thin clients.
SSH协议
ssh-keygen的使用方法以及ssh-keygen参数说明
Linux系统下的ssh使用(依据个人经验总结)
scp files from local to remote machine error: no such file or directory
sshd_config 中文手册
Enabling Public Key SSH Authentication on Your VPS
SSL/TLS协议
SSL(Secure Sockets Layer 安全套接层),及其继任者传输层安全（Transport Layer Security，TLS）是为网络通信提供安全及数据完整性的一种安全协议。TLS与SSL在传输层对网络连接进行加密。
ITU简介
The ITU coordinates the shared global use of the radio spectrum, promotes international cooperation in assigning satellite orbits, works to improve telecommunication infrastructure in the developing world, and assists in the development and coordination of worldwide technical standards. (世界级的技术标准制定组织）
ITU:international telecommunication union,又臭又长的名字，不过好歹算是做到了望文知意，国际电信联盟—联合指定，负责信息与通信技术。组织原名：International Telegraph Union 。
在刚开始，本来只有一个机构。这里的本来是指1865年，在巴黎的国际电报大会上成立成立国际电报联盟（International Telegraph Union ），负责国际有线电报线路协议的制定。后来（1895）出现了无线电报技术，1906年出现所谓的无线电报联盟，二者1932年合并成为国际电联并于1947年成为联合国指定机构，
国际无线电报联盟(The International Radiotelegraph Union) 于1906年在第一次国际无线电报大会上非正式成立。1932年，两家公司合并为国际电信联盟。1947年成为联合国指定机构。The CCIR—Comité consultatif international pour la radio, Consultative Committee on International Radio or International Radio Consultative Committee—was founded in 1927.In 1932 the CCIR and several other organizations (including the original ITU, which had been founded as the International Telegraph Union in 1865) merged to form what would in 1934 become known as the International Telecommunication Union. In 1992, the CCIR became the ITU-R.
下设三个部门：
1.无线电通信部门Radio communication (ITU-R
2.电信标准化部门Standardization (ITU-T),T代表telecommunication—)——The International Telegraph and Telephone Consultative Committee (CCITT—from French），was created in 1956, and was renamed ITU-T in 1993.
3.电信发展部门Development (ITU-D)
常见网络的区分
虚拟存储器之存储器映射原理：
Html
HTML entity
HTML保留字和键盘中没有的字符需要用字符实体—实体名or实体编号替代，如copyright symbol→©:©
1.Html中style既可以做element,也可以做attribute
做元素时，<style>标签定义Html文档的样式信息，支持html的事件属性和全局属性，每个html文档中可以使用多个style标签
做属性时，style是全局属性,用户规定元素的行内样式（inline style)
-
如果没有使用`scoped`属性，则<style>标签必须位于head头部区域，即只能定义文档整体的样式
两者一般都是测试用来快速格式化This attribute and the<style> element have mainly the purpose of allowing for quick styling, for example for testing purposes.
2.<span>标签：an inline element used to group elements for styling purposes，like
for block-level elements.
3.the single most common source of HTML validation errors in otherwise well-marked-up web sites:<a>标签中的href属性的value，网址中有&符号，忘记转义—
&:(ampersand)CSS
SVG
Scalable Vector Graphics (SVG) is an XML-based markup language for describing two dimensional based vector graphics. SVG is essentially to graphics what HTML is to text.
SVG在HTML页面中的嵌入方式：通过三个标签嵌入或者直接嵌入
SVG 文件可通过以下标签嵌入 HTML 文档：<embed>、<object> 或者 <iframe>。
*<embed>标签是：html5引入，用于定义嵌入的内容，比如插件，所有浏览器都支持- <object>标签：定义内嵌对象，比如图像、音频、视频、Java applets、ActiveX、PDF 以及 Flash。
<!DOCTYPE html> <html> <body> <svg xmlns="http://www.w3.org/2000/svg" version="1.1" height="190"> <polygon points="100,10 40,180 190,60 10,60 160,180" style="fill:lime;stroke:purple;stroke-5;fill-rule:evenodd;" /> </svg> </body> </html>