Performance-enhancing proxy

A Performance Enhancement Proxy Server or Performance Enhancing Proxy (PEP ) to German about proxy server to improve performance, is a proxy server, the TCP accelerated at the transport level when Internet services are mediated via satellite links.

TCP is connection-oriented and designed to immunity. Shipping and size of data packets depend on the reaction of the receiver. For mediation via satellite link, it is not suitable. The signal propagation delays cause long latency periods, until an acknowledgment by the recipient. On the other hand, the line quality is so good that could be dispensed with acknowledgment from the recipient.

A PEP sends replies to the sender, which may stem from the receiver. He engages in TCP and changed the header accordingly. At the same time it signals a high quality of service to request larger data packets. The answers cause the transmitter to send more data packets, even though the receiver has not reported at all. Together with the second server on the opposite side of the satellite assume the PEP data throughput over the radio path and ensure that the connection for the transmitter and receiver appears as a normal TCP / IP connection.

Encrypted data such as IPsec VPN, which also extend to the TCP header, a PEP can not accelerate. One solution is to restrict the encryption on the payload and the TCP / IP header does not involve (SLE Selective Layer Encryption / Application Layer Security ). Another solution shifts the PEP prior to the VPN server, but the link PEP VPN could be exposed to attacks. The methods are not standardized and are partially protected by patents.

In DVB- S protocols Unidirectional Lightweight Encapsulation ( ULE ) and the Generic Stream Encapsulation ( GSE) used to come to encapsulate at the network level IP data packets and thus reduce the data header.