We tested SIP products by building a large, multi-vendor test bed at the NetWorld+Interop InteropNet Labs Hot Stage facility in Belmont, California. Using Extreme Networks and Cisco Power-over-Ethernet switches, as well as PoE equipment from ADC, we started with a basic switched network for all vendor equipment to connect to. We attached a wireless network switch from Aruba Networks and three access points provided by Aruba Networks to give Wi-Fi SIP phones an avenue onto the network. We also used the Extreme Network switches as IP routers between parts of our network, and dropped a Juniper Networks NetScreen 5GT-Wireless firewall to protect us from the rest of the Internet.

To provide basic services such as DNS and DHCP, we added a Red Hat Linux server running common open source tools.

Once the network was stable, we began to install SIP phones and analog telephone adapters as well as SIP proxy servers. In all, we tested seven SIP proxy servers. In some cases, we used 1U servers provided by 1hotwebserver.com to install the SIP proxy software; in others, vendors provided the hardware that supported their own proxy software.

We tested basic calling within a SIP proxy server and across SIP proxy servers, then called in the vendors of both SIP proxy servers and phones for two days of intensive testing. We created a four-stage plan, moving from basic calling up to cross-server interoperability and worked as a large group to complete full N-by-N testing of each phone with each other phone and with each feature we wanted to test.

In addition to this feature interoperability testing, we also ran two other smaller interoperability tests, one using videophones and a second using firewalls. The videophone test did simple testing to see if we could even complete calls and start sending quality two-way video between phones. The firewall test checked to see if firewalls could actually watch the SIP datastream and properly control SIP traffic crossing the firewall.

We also used protocol analyzers from WildPackets and ClearSight Networks, as well as the Abacus SIP call generator from Spirent Communications to help debug and test our SIP test bed.

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