messages exchanged between the client's and server's computers will never be lost, damaged, or received out of order. [1]

w几乎所有的HTTP通信都由TCP/IP承载。

HTTP The Definitive Guide

Just about all of the world‘s HTTP communication is carried over TCP/IP, a popular layered set of
packet-switched network protocols spoken by computers and network devices around the globe. A
client application can open a TCP/IP connection to a server application, running just about anywhere
in the world. Once the connection is established, messages exchanged between the client‘s and server‘s
computers will never be lost, damaged, or received out of order.
[1]

[1]
Though messages won‘t be lost or corrupted, communication between client and server can be severed if
a computer or network breaks. In this case, the client and server are notified of the communication
breakdown.

messages exchanged between the client's and server's computers will never be lost, damaged, or received out of order. [1]

原文：http://www.cnblogs.com/yuanjiangw/p/6286441.html