British Telecom recently announced that they intend to assert patents they hold covering the Session Initiation Protocol (SIP) needed to connected a SIP-based system (like Asterisk) to the PSTN (traditional phone) system. They have launched a licensing program and campaign, trying mainly to scare small companies into paying up.

Some of the patents are listed in the link. What prior art can be found to invalidate these?

  • Just skimming through their patents, it directly cites the applicability to mobile telephony (not VoIP) with many strikingly similar parallels to how GSM works which has an entirely other working group. Jul 26, 2013 at 7:49

1 Answer 1


The link has a handful of patents listed. The boilerplate agreement linked from that page has an exhibit C with 99 patents listed. Just to hire a search firm to study all of those and try to find published documents that anticipate or tend to show obviousness for them would cost way more than the $50k BT wants for a fully paid up license. Maybe most of them are irrelevant "upon inspection" and the task can be narrowed. Ask Patents might be a good forum for experts in the VoIP world to come together to divide the problem up and possibly win.

  • SIP is covered under IETF RFC 3261 -tools.ietf.org/html/rfc3261. In addition, RFC 3667 under section 7.2 "Rights to use contributed material" requests that contributors give assurances to allow use and derivative works under 7.3. Unless BT is claiming they've made proprietary changes to the protocol, I don't see this holding water. Jul 26, 2013 at 7:27
  • The original RFC goes back to March 1999 under RFC 2543 with Bell Labs being the only notable corporation of authorship. Jul 26, 2013 at 7:36

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .