 to circumvent efforts to block them from reaching particular web sites. COMPRESSION Compression reduces the size of video, data, image, and voice files. This decreases the amount of network capacity needed to transmit files. Compression increases through- put without changing the actual speed of the line. Compression When compressed music and video files are downloaded from the Internet, video or voice is re-created at the receiving end by using less-powerful, lower-cost but acceptable asynchronous compression. Streaming com- pression algorithms assume that the end user will have less processing power to decode transmissions than the developers and broadcasters that encode the video and audio. Enterprises typically use synchronous compression to re-create text, image and numeric files exactly as they were sent by using web acceleration and optimization. (See the section "Wide Area Network Acceleration and Opti- mization," later in this chapter.) With compression, a song can be downloaded in seconds rather than minutes because fewer bits need to be sent. At the receiving end, compatible compression soft- ware or hardware re-creates the compressed chunks into close to or the same image or sound that was sent. Text is re-created exactly as it was before it was compressed SO that numeric information or product information is not altered. However, when it's received, compression might re-create video and voice in varying degrees of lower video resolution or voice quality with acceptable, often barely noticeable, alterations. Compression used with text and facsimile often reduces the amount of data to be transmitted by removing white spaces and by abbreviating the most frequently appear- ing letters. For instance, repeated letters are abbreviated into 3-bit codes instead of 8-bit codes. In a similar fashion, one method of video compression transmits only the changed image, not the same image over and over. In a video conference, nothing is transmitted after the initial image of a person until that person moves or spea