 organizations to link domestic and international offices with headquarters via high-speed data links. (See Chapter 4, "Carrier Networks," for information on carrier network services.) Previously, these organizations only had access to centralized e-mail. More recently, organizations have centralized an increasing number of IT func- tions at their headquarters to reduce or eliminate staffing expenses at remote offices. However, when the ability to access applications and files over the WAN is added, linking their remote offices to their headquarters, they often find that users have to sit and wait while files are downloaded. This becomes a critical issue as organizations grow, centralize IT services, merge with other companies, or add remote sites to their networks. It's not unusual for enter- prises to connect their headquarters with as many as 80 remote sites, including branch offices, small sales offices, and warehouses located in their home country, as well as in international locations. Wide Area Network Acceleration and Optimization WAN acceleration and optimization, also referred to as application acceleration, improves the performance of data lines between enterprise locations. It is done by a combination of improved compression and the elimination of delays caused by the most commonly used protocols. Even with high-speed connections, delays can occur when users access data remotely. Certain protocols are at the root cause for many of the long waits for requested documents and applications to download to personal computers. Download- ing delays are referred to as latency. TCP, HTTP, and HTML are the most commonly used protocols that contain many error control messages that cause latency. (See the Glossary for definitions of HTTP, HTML, and TCP.) A number of companies, including Cisco Systems, Riverbed Technology, and soft- ware start-up Certeon Inc., offer WAN optimization and acceleration. Gareth Taube, former vice president of Worldwide Marketing at Certeon Inc., refers to the afore- mentioned protocols