SMB Internet Telephony PBXi System SIP 2.0 (RFC3261), Max. 30 SIP IP phones/10 concurrent calls, FXO/FXS interfaces, Forward to voice mail on no-answer, internal 450 minutes, Configurable IVRi prompts.

Internet Telephony PBXi System SIP 2.0 (RFC3261), Max. 200 SIP IP phones/50 concurrent calls, FXO interface for PSTNi, Forward to voice mail on no-answer, Configurable IVRi prompts. Up to 4 PBXs cluster.

Carrier-class SIP based applications platform that provides standard, built-in telecommunications features such as name and number translation, private dial plans, call forwarding, and call routing.

A high performance and scalable RTPi media proxy server supporting VOICE and VIDEO. Should be used with LanScape SIP proxy servers. Allows you to overcome all NATi traversal issues. Easy to deploy.

Full functional scalable SIP Proxy that allows you to overcome all NATi related issues. Use with the LanScape VOIP Media Proxy to obtain a fully scalable VOIP domain solution. Supports VOICE and VIDEO.

CPLi-enabled

Full SIP server suite, which includes proxy, registrar and location servers.

perl-written with support for perl plug-ins

The HSSi SIP Server is a carrier grade RFC 3261 compliant SIP application server with built in support for proxy,registrar,redirect, conferencing and more. It comes with a complete extensible framework

A presence management server collecting, handling and supplying presence context

The SIP B2BUAi provides developers a scalable, reliable, and feature-rich environment for rapid service creation for next generation convergent networks.

The FacetPhone server is the heart of the FacetPhone IP-PBXi system. The server runs on Linux or UNIX platforms. The server controls media gateways and IP phone endpoints with the MGCPi protocol.

CPLi; Java; see also the the location server

Asterisk is an Open Source, full featured hybrid
TDM and VoIPi PBXi and IVRi platform. It allows you
to seamlessly integrate TDM (T1, PRI, FXS, FXO) and
VoIP (IAX, SIP, H.323) technologies in a single PBX

SIP CGI-BIN support; see SipCom (http://www.sipquest.com) for licensing.

Developed with IBM, the CIRPACK HVS SoftSwitch handles up to 5 millions BHCA and 6000 E1, delivering advanced Class-4 and Class-5 services over any ATM, IP and TDM networks.

OnDO SIP Server is a server based on the SIP protocol which provides proxy, registrar, and NATi services.

BEA WebLogic SIP Server is an integrated J2EE-SIP application server, providing a service creation and execution environment for converged HTTP-SIP Servlet applications in an IMSi network architecture.

aseVoice Vanilla is a J2EE-based SIP Server that functions as a Proxy, Registrar and Presence Server. Built on top of BaseStack 2.0, an implementation of the JAIN SIP API v1.1.

CCS connects with Avaya CM 2.0 to support the deployment of SIP telephony. Avaya CM becomes a telephony server that can be accessed not only by an Avaya SIP telephone, but by any SIP-compliant device.

partysip is a GPL -open source- SIP proxy server. It's simple, compliant and easy to install. That makes it suitable for low SIP traffic management.

MOSAICA is a scalable carrier-class IP Centrex and convergent applications service platform with virtual PBXi, unified messaging, CTI, ACD, IVRi, groupware and mobile services for business customers

H323/SIP platform, including Softphone (also web-based), presence server, softPBX, gatekeeper, SNMP monitoring etc.

3CX Phone System for Windows is a SIP based IP PBXi/VOIP Phone system. Both commercial and free editions are available.

UNIX, Sun Solaris

High-performance, flexible SIP server. Linux/Solaris/BSD. SMS, accounting, web
provisioning, etc.

802.11b Wireless SIP Phone. Great product. See http://www.voip-info.org/tiki-index.php?page=Asterisk+phone+Zyxel+P2000W for important up-to-date information on compatibility.