The Gizmo Project (http://www.gizmoproject.com) is a competitor to Skype that is owned by the company SIPphone, Inc. Like Skype, the Gizmo Project also offers a client download for Windows, Mac OS, or Linux with additional services that allow a call to the PSTN (Gizmo Out) as well as incoming calls with a static phone number (Gizmo In). The Gizmo interface is shown in Figure 10-3.
Instead of a proprietary VoIP network such as Skype employs, the Gizmo Project supports open protocols and a SIP-based network for VoIP calls. This is handy for administrators who want to integrate their Gizmo services with other SIP devices and software (for example, Asterisk). This also means interoperability with other users in SIP networks. Upon login, Gizmo communicates through HTTP or HTTPS to configure itself with a SIP proxy server and loads an initial list of RTP relays. The RTP relay is similar to a Skype supernode and is used when direct communication between two Gizmo nodes fails.
The Gizmo project softphone uses the following port numbers :
Incoming UDP port 5005 RTCP (Real-Time Control Protocol)
Incoming UDP port 64064 Gizmo default for SIP messaging
Incoming UDP port 5004 Gizmo default for RTP traffic (the actual voice messages)
Outgoing TCP port 7070 SRS relay and Jabber protocol
All outgoing UDP ports above 1023
These defaults are customizable in the Advanced section of the Gizmo Project Options dialog, shown in Figure 10-4.
For all of its adherence to VoIP standards, there is still a very big question mark on Gizmo's use of encryption. According to documentation on the website, Gizmo does, in fact, employ standards-based encryption on conversations; they just won't say exactly what encryption scheme it is (http://forum.gizmoproject.com/viewtopic.php?t=393). Because the Gizmo developers have yet to release any information on the strength or architecture of the crypto built in to the softphone, some in the VoIP industry are leery of the potential problems that might be uncovered once a more thorough security analysis is performed.