Minisip, with a core/UI separation and encryption, alpha version for Nokia 770.Linphone, with a core/UI separation, the GUI is using GTK+ libraries.Ekiga, formerly known as GnomeMeeting, GPL.PfSense FreeBSD based PfSense Firewall has QoS that properly tags voip traffic and a sip proxy package that is available for NATed endpoints.Linux Netfilter's SIP conntrack helper fully understands SIP and can classify (for QOS) and NAT all related traffic.Fortinet All FortiGates running v280/v300 Builds.Secure Computing's Sidewinder 7 firewall includes a SIP proxy.Secure Computing's SnapGear firewall includes the siproxd SIP proxy.Cisco PIX/ASA firewalls include complete SIP support.Ingate SIP Transparent Enterprise Firewalls and SIParators - Enabling global SIP communication on the enterprise LAN.Intertex SIP Transparent Routers, Firewalls and ADSL modems - For broadband deployments and the SOHO market.Check Point's VPN-1 firewalls include complete SIP support for multiple vendors.