Pretty cool name, huh? If you're going to create a new VoIP or unified communications attack, you want to have one with panache and it is hard to get a name with more impact than the 'INVITE of Death'.
That said, the attack itself is not nearly as impressive as the name. SIP is one of the prevalent protocols for VoIP and unified communications. The INVITE request is a function of SIP (Session Initiation Protocol). When a call is placed, the INVITE request is sent to the device being contacted. The receiving device can respond that it is TRYING, or that it is RINGING, or with OK and establish the communications session as a few examples.
The INVITE of Death attack is simply a denial-of-service (DoS) attack and it only works against one particular open source product- OpenSBC. Directing a malformed INVITE request to a vulnerable OpenSBC server will cause the OpenSBC server to crash.