Related Tools

This page presents external tools compatible with the OpenSAND platform.


PEPsal [1] is an integrated, multi-layer, transparent TCP Performance Enhancing Proxy which splits the connection into two parts, making use of Linux TCP enhancements when sending data, and largely improving performance in links with different characteristics.

A PEP (Performance Enhancement Proxy) is specially helpful for satellite communications since it allows to isolate (from a TCP point fo view) the satellite segment and improve degraded TCP performance caused by long satellite RTT.

In short, one of the main attractive features of a PEP is to simply split the TCP connection for avoiding the RTT impact on the growth of the congestion window.

PEPsal operates at three different layers (IP, TCP, and Application). It uses netfilter to intercept those connections that would involve a satellite links and "steals" the TCP SYN packet in the three-way handshake phase of a TCP connection, then pretends to be the other side of that connection, and initiate a new connection to the real endpoint, using a userspace application that directly copy data between the two sockets.

The PEPsal is classified as an integrated PEP, since it runs only on a single linux box that normally forwards packet between two or more networks, and can select which connections have to be enhanced by means of netfilter.

The PEPsal sources are hosted on the gitlab forge from the Net4Sat platform.