Ottawa-based network equipment maker Mitel Networks Corp. is suing rival Sunnyvale CA-based ShoreTel Inc. over communication-gear patents. Mitel contends that ShoreTel has infringed four Mitel patents relating to PBX Web control, remote user access, presence and phone-system architecture. The patents were issued in 1996 and 1997. Claiming innovation as its bread and butter, Mitel says it plans to assert its rights over its intellectual property.