November 6, 2008

SIP Goes Global?

By Jonathan Tombes

Companies that leverage Internet protocol (IP) technologies may rise and fall and rise again, but the protocols themselves - at least the successful ones - plod along, one request for comments (RFC) after another.

One phoenix-like IP network-based service provider that famously sought Chapter 11 bankruptcy protection in January 2002 only to revive as a strong tier 1 carrier today, Global Crossing, released news this week on both earnings and a standards-based service feature.

Third-quarter revenue figures announced yesterday (Nov. 5) were $667 million. From that figure, the company said adjusted gross margins were 54 percent. The market has been cheering today so far.

That's only one day in the life of a telecom provider that claims to serve 35-40 percent of Fortune 500 businesses, but it's a sweet snapshot, especially compared with the monumental corporate excesses and financial dysfunction of six years ago.

SIP Refer

The new feature announced this week was session initiation protocol (SIP) Refer, which Global Crossing stated "enables enterprises and IP-based application service providers to utilize their IP networks more efficiently while transferring incoming calls to the location or party best able to serve the caller's needs."

SIP is a signaling protocol nurtured since 1999 within the RFC process of the Internet Engineering Task Force. It is defined through some 150 different RFCs. The SIP Refer method is specified in RFC3515.

The feature looks like a double win, well-suited to an economic downturn: It both frees up a business customer's IP network capacity and enables automatic call transfers, requiring no attendant intervention.

It's another example of the protocol's versatility and simplicity.

Interop and trunking

The other side of SIP's widespread diffusion among IP endpoints, however, is concern over interoperability, a challenge that groups including the IETF, Broadband Forum and CableLabs (which incorporated SIP into PacketCable 2.0 in 2005) have recognized.

For now, SIP's entry point within cable networks appears to be business telephony. (See this case study on SIP Business Voice published in July.) Cox Business executives, including Kristine Faulkner, also have spoken favorably of SIP trunking.

For more details on SIP trunking, click here.

But for those MSOs whose focus on small-to-medium businesses (SMBs) puts them at the other end of the spectrum from Global Crossing, the advice tendered in August from ClearCable Networks Rob McCann may yet apply. In this article, McCann recommends that operators "lead ... with simple analog line and trunk replacement products instead of emerging IP multimedia solutions such as SIP trunking."

That said, IP networks within businesses of all sizes should continue to mature - as will SIP itself, one RFC at a time.

- Jonathan Tombes

Read more news and analysis on Communications Technology's Web site at www.cable360.net/ct/news/.