SIP Interoperability Test Event FAQ

General Questions

What is a SIP interoperability test event?
A SIP interoperability test event is a meeting of developers of SIP implementations. At the SIP interoperability test event, groups of implementors test their implementations for interoperability with other groups. A interoperability test event usually lasts about three days and takes place roughly every four months (April, August, December). It has been proposed to extend the interoperability test event duration to four or five days.

"The interoperability test event is for non-competitve, friendly testing of possibly incomplete code - not a certification environment or anything of the sort. It is meant as someplace people can come to, and test their code at, without feeling the pressure of success. There should be no business repercussions from the results of the bakeoff." (Jonathan Rosenberg)

Who can attend SIP interoperability test events?
Only implementors of SIP-related software and hardware are allowed to attend the interoperability test event. Groups must have an existing implementation, rather than just a plan to implement SIP. Journalists, sales & marketing staff and recruiters are explicitly not welcome.
Is there a limit on the number of people that can attend?
To allow reasonable communication and coordination between participants, each organization is limited to two (2) participants per product (distinct software or hardware implementation, with distinct SIP code base). Exceptions can be made if space is available.
Are there presentations or talks at the interoperability test event?
No, the interoperability test event is not a training event, trade show or industry conference. There are no presentations or panel discussions, just groups testing equipment and software.
What kind of equipment can be tested?
SIP user agents, proxy servers, software, phones, gateways, voice mail systems, protocol testers, ... Generally, both SIP and, to a lesser extent, RTP functionality is tested.
Is there a minimum requirement for participating?
There is no entrance exam and early implementations are welcome to participate. However, other groups may not appreciate being "used" to debug basic program functionality with you. Thus, it is generally expected that you have done your "homework" and tested basic call setup and, preferably, have a parser robust enough to handle most of the "torture tests" and test messages.
Where have SIP interoperability test events been held?
# Host Date Organizations Attendees
1 Columbia University, New York, NY April 8-9, 1999 16 36
2, Melville, NY August 5-6, 1999 15 39
3 Ericsson, Richardson, TX December 6-8, 1999 31 teams (26 companies)
4 3Com, Schaumburg (Chicago), Illinois April 17-19, 2000 46 teams (36 companies) 108
5, Melville, New York August 8-10, 2000 50 teams (44 companies) 143
6 Sylantro, Santa Clara, CA December 5-8, 2000 57 companies 202
7 ETSI, France March 25-30, 2001 58 companies 150
8 Ubiquity, Cardiff, UK August 13-17, 2001
9 Nuera, San Diego convention center, CA December 2-7, 2001
10 Nextone, Washington, DC April 2002
11 August 2002
12 hotsip December 2002
13 HearMe April 2003
14 ETSI August 2003
15 open December 2003
16 ETSI April 2004
Is there an NDA to sign?
No. SIP interoperability test events operate on mutual trust and cooperation. We expect attendees not to reveal product features or bugs discovered during testing. The results of the interoperability test event are not published in identifiable detail, but a press release is issued identifying the participating organizations. Thus, if the existence of your work is secret, you are probably ill-advised to attend the interoperability test event.
Can my company release a press release after the interoperability test event or mention the interoperability test event in marketing material?
Yes, of course. However, please avoid the following:

You are welcome to say things about the number of companies participating in the interoperability test event, name the products that you tested, make general comments about the state of the SIP "industry" or your general experience at the interoperability test event, etc. We would like to avoid any impression that the SIP interoperability test event is anything other than a closed-door technical event. We would also like to be able to maintain a gentleman's agreement on these issues, without having to issue formal guidelines.

Where are interoperability test events held?
Organizations volunteer to host the interoperability test event either in their own facilities or in a nearby hotel, depending on available space.
Where are SIP interoperability test events announced? Is there a mailing list?
SIP interoperability test events are announced on the SIP website, the SIP interoperability test event pages and the SIP mailing list. There is also a specialized mailing list for SIP implementors, (subscribe by sending email to, with subscribe sip-implementors foo@bar in the message body.)
What happens at the SIP interoperability test event?
Generally, interoperability test event participants alternate between two types of interoperability tests, namely pair-wise testing and larger demos. The hosts or other volunteers gather implementation information ahead of time, classifying implementations into UAs and proxies, with basic, intermediate and advanced ranking in each category. Depending on the interoperability test event, participants either find other implementations with similar capabilities or pairings are assigned ahead of time.

In addition, a number of demo scenarios are set up where larger groups of organizations get together to test more advanced scenarios.

There's often also a general discussion of any problems related to the SIP specification which may then be collected for presentation to the SIP WG.

Is there a interoperability test event winner?
Yes, hopefully every attendee wins by improving the robustness of their implementation. Typically, bugs are fixed even during the interoperability test event. There is no competition for the best implementation. However, if you expect other financial rewards, you are advised to contact the real interoperability test event instead.
Who is responsible for SIP interoperability test events?
Informally, Henning Schulzrinne coordinates scheduling and venue. Hosts are responsible for local arrangements. A technical program committee handles the technical aspects such as interoperability tests.

For Attendees

How much does it cost to attend the interoperability test event?
Hosts are free to charge a fee to recover their direct costs (such as food and off-site room rental costs); corporate hosts for interoperability test events 3 and 4 have not charged attendees, while earlier hosts charged about $100/attendee. It is a tradition that attendees from not-for-profit organizations are admitted for free. SIP interoperability test events are not intended to generate profit for the host; it is expected that hosts provide staff resources without charge.
Do I need to bring my own computer equipment?
Yes, only 10/100 Mb/s Ethernet connectivity (at least one port per attendee) and power will be provided. Hosts will provide both static IP addresses and DHCP. Sometimes, hosts can provide other networking facilities, such as T1, but that requires early coordination with the host.

Other things that you may want to bring along:

Last updated by Henning Schulzrinne