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.

Compression engine

A compression engine as part of the data center appliance compresses the aggregated packets that are in the highly efficient IP accelerator appliance buffers. This provides an even greater level of compression efficiency, since a large block of data is compressed at once rather than multiple small packets being compressed individually. Allowing compression to occur in the LAN-connected appliance frees up significant CPU cycles on the server where the application is resident.

Overcoming packet loss

The largest challenge in the TCP/IP performance improvements centers is the issue of packet loss. Packet loss is caused by network errors or changes better known as network exceptions. Most networks have some packet loss, usually in the 0.01 percent to 0.5 percent in optical WANs to 0.01 percent to 1 percent in copper-based Time Division Multiplexing (TDM) networks. Either way, the loss of up to one or more packets in every 100 packets causes the TCP transport to retransmit packets, slows down the transmission of packets from a given source, and re-enters slow-start mode each time a packet is lost. This error recovery process causes the effective throughput of a WAN to drop to as low as 10 percent of whatever the available bandwidth is between two sites.