Cisco Systems' Cisco Systems CallManager, Alcatel's OmniPCX R5, 1Lx, Nortel Networks' Succession 1000M, and Avaya's S8700 Media Server are reviewed large IP-PBXs. All the vendors support an H.323- to-SIP gateway and compelling productivity-enhancement features. However, security and management concerns are still to be addressed. The editors' choice is CallManager, which earns the highest scores for endpoints, management and administration, and performance. The four reviewed IP-PBXs all support 1,000 or more stations, and they were evaluated for architecture, including redundancy, hot swappability, ease of scalability, and so on; endpoints; management and administration; features; performance, including call quality and speed of failover; and security, for which Avaya S8700 got the highest marks, especially for its support for IP phone-to-IP phone encryption on voice RTP streams. Cisco's high-end touchscreen color phone has a cable with a lock on the end that can be secured to a stationary object. All IP-PBXs reviewed failed at least one denial of service attack, but the type of failure differed from product to product. Alcatel OmniPCS does not support SSL, SSH, or encryption. However, OmniPCS does support automatic VLAN assignment for its phones. Nortel Succession 1000M does not support SSL or encryption on its Element Manager, but Nortel's IP phones have no open TCP ports, and they are not open to attacks that need a port number. Nortel Succession gets kudos for its Equipment LAN (ELAN), a configuration in which call server, media gateway, and signaling server communicate with each other.