NORTH ANDOVER, MA (April 13, 2010) - The SIP Forum has announced that its next SIP Interoperability Testing event, SIPit 26, will be held May 17-21, 2010 in Kista, Sweden. The event will be hosted by Edvina and TANDBERG, and sponsored by Intertex, Ingate, .se, and the IPv6 Forum as an association sponsor.