Acme Packet, a Woburn, Mass., maker of session border controllers, this week announced it has received $15 million in a second round of venture funding.The company also announced that Global Crossing is using its gear and a partnership with Class 5 switch replacement vendor MetaSwitch.Acme Packet has now accumulated $31 million in funding since its founding in 2000. The latest round comes courtesy of new investor Advanced Technology Ventures and previous backers Canaan Partners and Menlo Ventures.The fresh financing will be used to expand sales, support and engineering\/quality assurance.Acme Packet is one of several providers of session border controllers, devices that regulate bandwidth, and maintaining service-level agreements and quality of service as traffic traverses disparate corporate and service provider networks through firewalls and network address translators. Others in this market include Jasomi, Kagoor, MediaRing, Netrake, Newport Networks and NexTone.Some vendors, such as Jasomi, are increasingly focused on enterprise networks, whereas Acme Packet is squarely carrier-focused.Acme Packet offers two products. One is Net-Net Session Director, which handles security, service assurance and other tasks at the border of IP nets. It supports standards such as MGCP, Session Initiation Protocol and H.323.The other offering, called the Net-Net Session Router, is a SIP routing engine.\u00a0Acme Packet stands apart from competitors in terms of its number of paying customers (more than 20), variety of control features, and carrier-class attributes, such as high availability, says Jim Hourihan, the company's vice president of marketing and product development. Carriers are using Acme Packet's offerings to support peering arrangements and provide hosted services, among other offerings.VoIP providers Fusion, in Japan, and Capcom in Spain are among Acme Packet's customers.The equipment maker addresses sticky issues that carriers are dealing with as they ramp up advanced IP services, says Bob Hower, a partner with new Acme Packet investor Advanced Technology Ventures. Demand for Acme Packet gear is being driven by carriers that want to deal in IP rather than TDM; and IT customers intrigued by IP Centrex and other next-generation telephony services, he says.Acme Packet's products were designed to handle some of the early problems being faced by VoIP service providers, such as getting traffic through firewalls. But they also address less-expected issues, such as protocol mediation between equipment even within the same carrier network, Hower says.Hower expects Cisco and other established carrier equipment suppliers to claim support for at least some of the features offered by upstart session border controller makers. However, carriers might find there will be a good reason to have a third-party supplier providing such technology, serving as an intermediary between equipment already installed by the Ciscos and Sonuses of the world, he says.In the end, the emergence of Acme Packet and other suppliers of products designed to ease delivery of IP services should help Cisco and other makers of underlying IP gear, Hower says.The 50-employee company was founded by CEO Andy Ory and CTO Patrick MeLampy, who in 1999 sold their previous company, Priority Call Management.