Vonage has been sued by yet another company for patent infringement, this time by Nortel.

In a suit filed last week, Nortel alleged that Vonage had infringed on 12 of its patents, which broadly deal with click-to-call systems, with the management or architecture of VoIP system resources, and with call-tracing methods in packet-switched networks. All the patents involved in the suit relate direct to technology designed for VoIP telephony systems.

"Defending our intellectual property rights is a top priority for Nortel," said Nortel spokesman Sami Asiri. "That is why we are seeking damages and a permanent injunction against Vonage around the use of our technology."

The suit comes in the wake of a suit filed against Nortel by Vonage earlier this year that alleged Nortel violated three of Vonage's patents. Two of the patents involved in that suit concern multiplexed digital-packet telephone systems. The third patent concerns packet-switching communications systems. Vonage acquired these three patents from Digital Packet Licensing in 2006.

The Nortel suit caps a busy year for Vonage's legal team. Last month, the company announced it had reached a settlement in principle with AT&T less than a month after AT&T accused the VoIP provider of violating its patents for systems that let users make VoIP calls using standard telephone devices. Additionally, Vonage also recently reached settlements with Sprint Nextel for US$80 million and with Verizon in a settlement that could be worth as much as $120 million.

The company reported net losses of $160.5 million in the third quarter of this year, more than twice the $65.8 million loss it reported for the third quarter of 2006. Overall, the company has lost $266.6 million so far this year, and it has incurred net losses of more than $500 million in the past three years.

Commenting on the suit to the Associated Press, Vonage spokesman Charles Sahner said, "We always prefer to settle disputes amicably whenever possible."