David Stever, manager of communication technology services at PPL, knows that IP telephony is the future. He also knows that his company (formerly known as Pennsylvania Power & Light) has a massive investment in a traditional voice network. With 3,000 lines and a wiring infrastructure at its Allentown headquarters that Stever describes as "challenging," the utility selected an IP-enabled private branch exchange (PBX) telephone system from Nortel Networks when it decided to upgrade its network. "We needed to get our feet wet (with IP telephony), but we needed a proven, mature system," he says.
On the other hand, in 2001, when the Cancer Therapy & Research Center consolidated facilities and expanded its headquarters in San Antonio, the organization was working from a clean sheet of paper -- and opted for a pure IP setup from Cisco Systems Inc. Chief Technology Officer Mike Luter says the network's speed and manageability, along with the "increased mobility" enjoyed by physician end users, made pure-play the way to go.
These experiences neatly summarize the telephony choices IT organizations are making today. Legacy PBXs are rapidly being supplanted by IP-enabled "hybrids," which analysts say offer most of the advantages of pure IP systems (such as the ability to easily change extensions and to use a new generation of applications for activities like inventory management) while allowing companies to retain most of their existing infrastructures. But pure-play IP systems, unlike hybrids, let IT organizations manage one network structure rather than two and are useful in small regional offices where it wouldn't make sense to install a PBX.
Bottom line: Pure-play IP telephony is gaining traction primarily (but not exclusively) with organizations that are undergoing other major changes -- a headquarters move or consolidation, for example, or any major construction project that entails new cabling.
Hybrid PBX systems -- traditional PBXs that use special port cards to make IP telephone connections -- are favored by businesses seeking most of the benefits of IP telephony without having to rip out their existing voice network telephone systems. The final choice for IT organizations is driven as much by external factors, such as moves and the addition of remote offices, as by the two systems' benefits.
When the Cancer Therapy & Research Center consolidated its offices from three buildings into two and expanded its headquarters, where most of its 900 PCs and servers and 800 telephones reside, Luter's team evaluated hybrid PBXs from Avaya Inc. and Nortel before settling on an IP telephony setup from Cisco.
Luter says Cisco was a "premium environment," but other factors offset that expense. For starters, the center saved more than US$58,000 by running a single wire for voice and data. Cisco's history as a data networking vendor appealed to Luter because the center routinely transmits enormous medical imaging files between facilities. Another benefit is the simplified help desk structure that comes with a single data-and-voice network.
"We've got Windows, Unix machines and Macintoshes, so our help desk faces some pretty complex needs," Luter says. "At least now we don't have one group for the phones and one for the computers; IT supports everything." He adds that getting phone extensions set up for new hires used to take up to two weeks but is now accomplished in less than a day.
Addressing one widespread concern about IP telephony, Luter says the center built redundancies for its phone system into its storage-area network (SAN). Each facility has a redundant pair of Cisco SN 5428 SAN servers.
Some analysts worry that redundancy and fail-over, which have been honed for 100 years in the switched-circuit world, haven't yet been sufficiently addressed in IP telephony systems. "By their very nature, basic PBXs provide fail-over resiliency in the trunks going to the (telephone service provider's) central office," says Laurie Gooding, an analyst at Phoenix-based Synergy Research Group. "An IP system doesn't provide that."
Gooding adds that "some vendors have been slow" to provide redundancy in their IP signaling interfaces -- that is, the backup system that kicks in if a server goes down.
But NFL Films has used IP telephony for its 450 phones since July 2001, and Steve Eager, director of network and systems administration, believes he has planned for almost any problem -- with one possible exception.
The Mount Laurel, N.J.-based chronicler of professional football is on a Synchronous Optical Network (Sonet) ring with separate fiber lines into each of its two connected buildings. For redundancy, each building gets a voice gateway, a Cisco Catalyst 6509 switch and a Cisco Call Manager Server (the servers are clustered).
"We're fully redundant," Eager says, noting one exception: Each of the company's eight closet switches is homed to a single 6509 switch. "If we lost a closet switch, we'd lose the phones at that closet," he says, adding that this has never occurred.
Many analysts agree with Brian Strachman, an analyst at In-Stat/MDR in Scottsdale, Ariz., who says, "The fear factor in IP telephony is gone in the last year or so -- they've worked out most of the bugs. Whether you buy a (hybrid) system or a pure IP, you're safe in terms of redundancy."
One advance in current hybrid PBXs is peer-to-peer IP switching. In early hybrids, voice-over-IP (VOIP) communication involved translating from traditional voice time-division multiplexing (TDM) to IP, then back to TDM. This round trip introduced the possibility of poor voice quality due to latency. Peer-to-peer IP connectivity is "a cleaner way to accomplish VOIP," says Jay Lassman, an analyst at Stamford, Conn.-based Gartner Inc.
Vendor Pros and Cons
Some IT organizations opt for hybrid PBXs over pure-play IP systems even when they're moving toward full IP telephony. Bow Valley College in Calgary, Alberta, implemented IP telephony in January 2002. Shortly after sending out its request for proposals, the college narrowed its choices to Cisco, Nortel and Alcatel. IT manager Mike Shannon led a team that believed Nortel lacked a "clear strategy" on IP telephony, leaving Paris-based Alcatel and Cisco as finalists.
Misgivings over Cisco's experience with voice networks prompted Bow Valley to choose an Alcatel OmniPCX system. "Cisco concerned us because they weren't voice-based; we weren't sure they understood voice enough," Shannon says. "And we weren't thrilled at the thought of running our voice over Windows 2000 -- we need five 9s reliability for our voice traffic."
Shannon says the hybrid PBX offers the advantages of IP telephony -- simplified management with Alcatel's OmniVista network management tool, a single architecture and an automated move/add/change procedure -- with flexibility not found in pure IP systems, such as the ability to run fax machines from analog ports. Like other newer hybrid PBXs, OmniPCX supports analog, digital, IP, wireless and soft phones.
Thomas Dunkerley, IT communications manager at The Seattle Times, concurs with Shannon's assessment of the trade-offs between a data-centric vendor like Cisco, 3Com Corp. or Sunnyvale, Calif.-based Shoreline Communications Inc. on the one hand and a voice-centric vendor like Avaya, Nortel or Siemens AG on the other. When the newspaper decided to replace its 10-year-old Avaya Definity PBX, it explored Cisco's pure-play IP system and hybrid PBXs, and Avaya emerged as the leading hybrid candidate.
To Dunkerley and his team, all of whom had experience with telecommunications, a drawback to the Cisco products soon became apparent. At The Seattle Times, each phone includes three call "appearances," or number listings. PBXs use a single port for each phone; with Cisco, each appearance would count as a port.
"That would have tripled my licenses," Dunkerley says. He adds that this anomaly is probably an example of Cisco's roots in the data world.
The newspaper opted for Avaya, partly because it was the only vendor whose products comply with Americans With Disabilities Act guidelines (offering simultaneous audio and visual paging, for example), but Dunkerley says there were trade-offs involved.
"Avaya's not as focused on data as Cisco is," Dunkerley says, citing Avaya's Cajun P330 switching system. "My network techs tell me the basics and functionality are all there but that the Cisco user interface is cleaner, making management a bit easier," he says. The newspaper has moved 300 end users to IP phones, and 750 more are on tap for the next three months.
Enterprise telephony is moving toward IP; there is little doubt about that. The question is, Do you want to take one giant -- but irreversible -- step today, scrap everything and go for pure-play IP? Or do you want to take baby steps and install a hybrid PBX, bridging past to future? For NFL Films' Eager, the giant step worked. "You have your Windows guys doing PCs and servers, and your Cisco guy doing all your networking -- including phones," he says. "What's simpler than that?" w
Ulfelder is a freelance writer in Southboro, Mass. Contact him at firstname.lastname@example.org.
Hybrids, Layer by Layer
First-generation hybrid PBXs had a circuit switch at their cores. Port cards made it possible to use IP phones but not to take advantage of advanced applications designed for IP telephony.
Most PBX vendors today, however, offer systems that don't have an integral switching fabric. Today's hybrids have migrated to a packet-driven architecture that separates communications management from the core. They tend to be modular software stacks composed of the following layers:
- A voice layer, where actual voice traffic (nearly an afterthought) is directed to IP telephones, "soft clients" such as desktop PCs (with a headset plugged into their Universal Serial Bus ports, a common practice in call centers) and traditional phones.
- A feature-set layer, where features such as hold, forwarding and conference-calling are determined and controlled.
- An application programming interface (API) layer, which includes hooks for other applications such as CRM software and network management tools. These APIs are critical in today's modular world. An IT organization using a HiPath 4000 from Siemens, for example, might use Hewlett-Packard Co.'s OpenView management software and a Siebel Systems Inc. CRM suite. The HiPath 4000 includes APIs to make such integration easy, according to Joan Vandermate, vice president of product management at Siemens.
- A gateway layer, which must eventually be connected to a public switched telephone network, no matter how much corporate network traffic is IP-based. At the gateway layer, a physical device converts IP packets for transmission over DS0 circuits.
- A call-control layer, where the class of service (such as limitations on international dialing), security policies and a database of registered users are determined.