In the early days of the telephone, users had to put up with multiple, incompatible phone networks, which was not only inconvenient but costly. People often needed two or more phones on their desks to be able to reach other telephone owners, and redundant networks of telephone poles darkened the skies over major American cities.
Current VoIP applications are shaping up to be similarly inefficient. Without a single, global addressing scheme, VoIP networks operate as islands that cannot be easily connected.
The answer, some say, is IPv6. By providing unique addresses to trillions of IP devices, IPv6 will ultimately enable more efficient direct connections between VoIP users, regardless of the network they use.
“IPv6 will allow carriers to offer VoIP services more efficiently” and to voice-enable other federated peer applications such as IM, explains Tom Kershaw, vice president of VoIP services at VeriSign. The problem, Kershaw explains, is that today’s enterprise VoIP systems rely on multiple means of addressing, including phone numbers, device IDs, and SIP IDs. So all calls, whether internal or external, must be routed through a directory server on the home network rather than directly to the end point.
“The challenge of setting up real-time [public network] calls is you’ve got 100 milliseconds to set that call up, so you really need efficient addressing,” Kershaw says. For VoIP calling from office to office, or outside of highly controlled homogeneous environments, he adds, “You want to call on the public network,” with a universal global addressing scheme enabled by IPv6. “It’s a pure-play cost-and-efficiency issue.”
Current VoIP routing is further complicated because many devices’ IP addresses are not routable, instead using NAT as an intermediary to the public network. This complicates end-to-end VoIP routing, requiring inefficient on-the-fly translation among multiple addressing mechanisms. By eliminating the need for NAT, IPv6 can cut out the middleman and turn VoIP into a more efficient, edge-oriented application, with each person having a unique IP or “public root address” for fast direct connections.
IPv6 will also provide a separate quality boost to VoIP thanks to its new 20-bit “flow label,” which allows layer 3 routers to identify a stream of packets as a voice conversation, explains Cody Christman, director of product engineering at Verio.
“If you and I are talking using IPv4 and a bunch of other people jump on, the router just gets overwhelmed with too many prioritized packets,” Christman says. “But with IPv6, it can actually understand the concept that you and I are talking, so it won’t let the next guy jump on. … You have one more knob to twist to hone in that quality of service.”
VoIP alone won’t trigger an IPv6 revolution, nor will IPv6 usher in the age of VoIP. But it’s clear that these two technologies have complementary roles to play in ushering in the future of IP-based telephony. The next time an engineer proposes upgrading the corporate network, a CTO might be wise to take that call.