Last but not least comes beta testing. This phase usually involves equipment installed at a customer's site, where it is subjected to the customer's real-life or almost-real-life situations and environment. Herein lies a possible trap. Customers tend to concentrate on applications that are pertinent only to themselves during beta testing, rather than performing a comprehensive test of the vendor's boxes across their entire suite of product features. For example, if a telephony application focuses on SIP-MGCP interoperability, then H.323, SS7, and whatever else the switch supports will not be tested. Therefore, it is imperative to concentrate on complete functionality and performance coverage before the beta phase, or possible lapses will be found later and will be expensive to fix. This is an excellent time to see the degree to which the customer's firewalls will affect the designed-in performance.