TCP as a transport layer has several limitations that cause many applications to perform poorly, especially over distance. These include: window size limitations for transmission of data, slow start of data transmission, inefficient error recovery mechanisms, packet loss, and disruption of transmission of data. The net result of issues is poor bandwidth utilization. The typical bandwidth utilization for large data transfers over long-haul networks is usually less than 30 percent, and more often less than 10 percent. Even if a chance of upgrading the last miles even at very high costs exists, the effective increase would be only 10 percent of the upgraded bandwidth. Hence, upgrading networks is a very expensive proposition.

A new technology called the ‘Application Acceleration’ has emerged, which accelerates the Internet applications over WANs using the same Internet infrastructure, circumventing to some extent the problems caused due to lack of bandwidth.

Application accelerators, as the name suggests, are appliances that accelerate applications by reengineering the way data, video, and voice is sent/transmitted over networks. Application acceleration addresses non-bandwidth congestion problems caused by TCP and application-layer protocols, thereby, significantly reducing the size of the data being sent along with the number of packets it takes to complete a transaction, and performs other actions to speed up the entire process.

Application accelerators can also monitor the traffic and help with security. Some appliances mitigate performance issues by simply caching the data and/or compressing the data before transfer. Others have the ability to mitigate several TCP issues because of their superior architecture.

These appliances have the ability to mitigate latency issues, compress the data, and shield the application from network disruptions. Further, these new appliances are transparent to operations and provide the same transparency to the IP application as TCP/IP application accelerators have the following features using Layer 4-7 Switching.

Transport protocol conversion

Some data center appliances provide alternative transport delivery mechanisms between appliances. In doing so, they receive the optimized buffers from the local application and deliver them to the destination appliance for subsequent delivery to the remote application process. Alternative transport technologies are responsible for maintaining acknowledgements of data buffers and resending buffers when required.

They maintain a flow control mechanism on each connection in order to optimize the performance of each connection to match the available bandwidth and network capacity. Some appliances provide a complete transport mechanism for managing data delivery and use User Datagram Protocol (UDP) socket calls as an efficient, low overhead, data streaming protocol to read and write from the network.