Nortel Networks has launched a patent violation lawsuit against Vonage in the U.S. District Court in Delaware.

The Canadian telecommunications manufacturer alleges that Vonage infringes 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 directly to technology designed for VoIP telephony systems.

“Defending our intellectual property rights is a top priority for Nortel,” says 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 — numbers 4,782,485 and 5,018,136 — concern multiplexed digital-packet telephone systems. The third patent — No. 5,444,707 — 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 $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.”