Synthetic Packet Pairs (SPP) - Tool for passive round trip time measurement
Regular and frequent measurements of round trip time
(RTT) are important in test networks or overlay networks
(e.g. to evaluate network protocols), and they are also
becoming increasingly important in operational networks, such
as the Internet (e.g. to assess the quality of service for
highly interactive real-time applications).
Active probing techniques are possible but problematic. The
extra packet traffic imposed by active probes along a network
path can modify the behaviour of the network under test. In
addition, estimated RTT results may be misleading if the
network handles active probe packets differently to regular IP
In contrast, SPP provides frequently updated RTT
measurements using IP traffic already present in the network. SPP
measures the RTT between two measurement points without
requiring precise time synchronisation between each point. SPP
accurately measures the RTT experienced by any application's
traffic without needing modifications to the application itself or
the routers along the path. In addition, SPP works with
applications that do not exhibit symmetric client-server packet
exchanges (such as many online multiplayer games) and
applications generating IP multicast traffic.
This website provides a standalone open source implementation of SPP in C,
which works on Linux and FreeBSD.
SPP is also in the FreeBSD ports tree under benchmarks/spp, and post-v0.3.6 development is now publicly available on Bitbucket.
(Alumni: Lutz Mark, Thuy Nguyen, Brandon Tyo, Amiel Heyde, Atwin O. Calchand, David Hayes)