Today to sort out a problem we often encounter when learning computer network eight, hoping to help everyone learn more.
1. For many instant messaging applications, uses a hybrid architecture. Server is mainly used to track the IP addresses of users, but packets between the user and the user does not pass through the server, but sent directly from one user to another user. This rabbit have to mention dynamic IP, you can effectively hide your real IP.
2. The application is referred to as having a certain bandwidth-intensive requirements of the application. For example, now most multimedia applications (video player requires a certain type of application throughput in order to have good picture quality and playback), and elastic applications can use much less throughput available under the circumstances, or. E-mail, file transfer, and web transfer are all elastic applications. (What does it mean? For example, when we download a file, speed, speed does not affect our final result download, but will affect the final of download time, so the needle like this type of application, we just need to make sure it is the underlying protocol reliable transmission on the line, of course, no one will speed too fast), point to note here throughput ≠ network speed. Why do you say? Throughput rate is determined by the minimum value of all the links, and now the core of the network links are very fast, so why did we every household broadband can be positioned at different speeds depending on the price it? the main reason is the access network link rate much lower than the core network link rate, so the throughput will determine the access link, which is why when we do broadband, we may be required to do 10M, 50M, the reason one hundred meters of different specifications, ISP to price according to different specifications. Broadband sooner we do, the faster the rate of access link, the overall throughput is higher.
3. Today, the Internet will provide a good service for bandwidth-intensive applications by several good design skills, but it does not make any guarantee throughput and timing.
4. Because TCP requires "three-way handshake" and has a congestion control mechanism, establishing a connection requires time and congestion control will adjust the transmission rate of the sender according to the network situation, so for those larger throughput applications (such as video playback software) sometimes less suitable for TCP.
The data transport layer protocol, generally transmitted in plain text. If you want to encrypt the data, it is above the application layer of the TCP can provide SSL security, data is encrypted during transmission, the data is decrypted upon receipt. (Need to use a dedicated SSL socket)
6.Web and file transfer using TCP. These applications are the main reason is that TCP TCP provides reliable data transmission services, to ensure that all data reaches the final destination. Because Internet telephony applications (such as Skype) are usually able to tolerate some loss but require a certain minimum rate in order to work properly, so an Internet telephony application developers prefer to use UDP, so try to avoid congestion control mechanisms of TCP packet overhead and . However, because many of the firewall is configured to block configured to block (of most types) UDP traffic, the Internet applications are typically designed to fail on UDP traffic uses TCP as a backup.
7.web page is composed of objects. An object can be an HTML file, a picture, a video. These objects located by the URL. That is the basic framework of a web page is a basic HTML document, there is a reference to the individual objects inside.
8. The server sends the requested file to the client without storing any state information about the client. If a particular customer requests the same object twice in a matter of a few seconds, and the server will not just send the object for customers without a response, but a re-send the object to the customer. Just forget doing the same thing before, because the HTTP server does not save any information about the customer, so we say in English, HTTP a stateless protocol.