Gizmo Project

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.

Figure 10-3: Making a call with Gizmo

Architecture

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.

Network and Bandwidth Requirements

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.

Figure 10-4: Setting preferences in Gizmo

Security Issues

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.