Before a VoIP server goes live, engineers want to know how many calls it can absorb and how it copes when things go wrong. SIPp was designed precisely to answer those questions. This SIP traffic generator was originally written by engineers at Hewlett-Packard, with Richard Gayraud credited for the initial code and Olivier Jacques for code and documentation, and the old project site carries a copyright notice starting in 2004.
Today the project is looked after by its community on GitHub, where it moved from version 3.4 onwards. It is distributed under the GNU GPL, and the latest release, 3.7.7, came out on 31 December 2025.
What SIPp is for
SIPp behaves like one or many phones, only at a pace no person could keep up. You give it the address of a SIP device, a call rate and a scenario, and it opens sessions, waits for replies, measures delays and keeps a live count in the terminal of successful, failed and ongoing calls. The same tool can also sit on the receiving end and answer calls, so a proxy can be tested with one SIPp instance placing calls on one side and another taking them on the other.
Scenarios drive everything. They are XML files that describe, message by message, what the tool should send and what it expects back. Several come built in, including a basic calling client and server, variants using regular expressions or branching, and third party call control. For finer work you write your own file, inserting variables, pulling a header out of a response, adding pauses or branching on the status code received. This is how a behaviour seen at a customer site can be reproduced faithfully, malformed messages included.
On the transport side, SIPp talks UDP, TCP, TLS and SCTP, depending on the options chosen at build time. It can echo audio back, send an RTP stream or replay packets captured in a PCAP file, which gives a media relay such as RTPEngine real traffic to chew on. The 3.7 releases added, among other things, RFC 3339 timestamps, SNI for TLS connections and the ability to act as client and server at once, according to the notes published on GitHub.
SIPp does not monitor production, it puts it under stress. To see afterwards what the test traffic did, HOMER, which is in our software library, captures and indexes the SIP exchanges. General purpose generators such as Ostinato or Scapy craft network packets, but they cannot carry a full SIP dialogue that reacts to responses.
Who is it for?
The tool serves teams that build or operate SIP servers, IP PBXs, gateways or media relays. It turns up in load testing before launch, in automated regression suites run against each new build, and in reproducing an incident a customer has reported. Equipment vendors also rely on it to check interoperability between products.
SIPp has no graphical interface and assumes a solid understanding of SIP, since every message must make sense to whoever writes or adapts a scenario. It does not assess the audio quality a user would perceive either. The online documentation is still numbered 3.6, behind the code. On Windows it goes through the Cygwin environment and a manual build, and only Linux gets a binary that is ready to run.
Download SIPp safely
Official releases are published on the releases page of the SIPp/sipp repository on GitHub. Each one includes a static Linux binary, built on Alpine so that it needs no system libraries, a source archive and an automatically generated manual page. The repository also holds Docker files, one for that static build and another based on Debian with WolfSSL. Building from source uses CMake and a C++17 compiler, with flags for TLS, PCAP, SCTP or the GSL library. Documentation lives at sipp.readthedocs.io, while the old sipp.sourceforge.net site now only serves versions 3.3 and earlier.
The software is completely free and there is no commercial edition. Since its whole purpose is to fire thousands of requests at a server, a tampered executable picked up on a forum could aim at a different target or carry unwanted code. The official GitHub binary, or the package from your Linux distribution, is the only sensible source.
Frequently asked questions
Can SIPp test a production server?
Technically yes, but it is not advisable. A badly calibrated load test can overwhelm the live service. A dedicated test platform, or tight limits on rate and duration, is the safer route.
Do I need programming skills to use it?
Not strictly. The built-in scenarios are enough for a first test. Realistic cases do require writing XML files, which mostly calls for a good command of SIP.
Which licence covers SIPp?
The GNU GPL. The licence file in the repository specifies version 2 or any later version, and two files taken from another project keep their own permissive licence.
