IP PBXs scale for the enterprise

RIP PBXs aren't just small-office playthings anymore. With near-universal agreement that telephony will be carried within IP packets, vendors are preparing their next-generation PBXs with capacities and features they hope will position their products as competitors to classic enterprise-level PBXs.

A Mier Communications survey conducted last month showed that some IP PBXs can reportedly scale to 10,000 stations, whereas a year ago the average system supported a maximum of 50 to 100 stations. Mier Communications also found that the market is segmented into low-, midrange and high-end systems.

Vendors of classical PBXs have also entered this crowded field by adding voice-over-IP gateway cards and modules to "IP-enable" their existing PBXs.

As far as features are concerned, all vendors are branching out from basic PBX features such as hold, wait and transfer, by adding more advanced PBX features like modem relay and fax support, interactive voice response, billing and accounting, direct-inward-dial, elaborate call routing, least-cost routing and toll restrictions.

Miers detailed questionnaire went to 36 vendors that we believed were shipping or planning soon to ship IP PBX products. The systems go by a variety of names, including Telephony-over-IP exchange, Integrated Communications Server and IP Telephony Server.

We received 22 responses. However, not all were complete and some of the products didn't quite fit, so several were disqualified. The final participating vendor list was: 3Com, Alcatel, Cisco, Dialogic, Ericsson, Intecom, Inter-Tel, Avaya/Lucent, Mitel, NEC, Oki Network Technologies, Shoreline Communications, Tek Digitel, Vertical Networks, Vovida Networks and Vive Synergies.

Expanding capacities

As recently as late last year, IP PBXs generally supported just 100 or fewer stations and were targeted mainly at small-office and branch-office applications. We define "stations" as any connected device, including phones, PCs, faxes and others. Today, however, only 25% of the products surveyed top out at 100 stations. Approximately 30% support maximum capacities in the 101-to-216-station range, and nearly 20% support between 1,000 and 5,000 stations. Products in this midrange group include Lucent's Definity; Alcatel's OmniPCX 4400 and the Shoreline Communications System.

On the high end, there are systems that can support thousands of stations. For example, Cisco's AVVID can reportedly support up to 10,000 stations, and the company claims it is aiming at 100,000 users within the next five years. Cisco's AVVID targets the same high-end enterprise users as traditional PBX vendors such as NEC and Intecom do with their IP-enabled PBXs, but AVVIDD is based on an entirely different architecture. Cisco advocates replacing the traditional fixed-bandwidth, time-division multiplexed PBX switch fabric with a distributed IP network.

Mier Communications has not yet tested many of the new high-end IP PBXs or IP-enabled PBXs, and cannot substantiate the capacity claims. It is clear from its research that the capacities reported by IP-enabled PBX vendors represent the maximum combination of voice-over-IP calls along with regular public switched telephone network connections. So the high capacities claimed for many of the IP-enabled PBXs are not just for voice-over-IP calls.

The new, old players

As recently as a year ago, a handful of vendors dominated the IP PBX market. Early entrants included Cisco, which had acquired Selsius; 3Com, which had acquired NBX; Shoreline; and Vertical Networks. Most of the traditional PBX vendors such as Intecom, Mitel, NEC and Lucent were conspicuously absent.

That changed in June 1999, when Lucent introduced voice-over-IP and IP add-on components for its popular Definity PBX line. Today, most of the well-established PBX vendors, including Ericsson, Intecom, NEC and Mitel, are offering pathways so that their large installed bases can migrate to IP.

Even though their IP-enabled products are based on older technology, which has to be retrofitted for IP convergence, classic PBX vendors have some advantages over the newer server-based integrated communications platforms. Their products are widely installed, and they have established track records for products and customer service. They also offer hundreds of PBX features that their newer, IP-PBX cousins don't yet support. These include "do not disturb" functions, feature keys, paging and off-hook voice announcement.

The next-generation IP PBX vendors counter this feature argument by saying that most of the hundreds of features supported on classic PBXs are seldom used. A typical company probably uses fewer than 10, according to Mier Communications research. Nonetheless, enterprise users are loath to give up anything to migrate to IP.

Key features

In terms of basic PBX features, IP PBXs are on par with their IP-enabled counterparts. The IP PBXs we surveyed support call hold, call waiting, conferencing, call transfer and call forwarding.

Many of the IP PBX products also support more advanced features. Voice mail is widely available, usually as an integral feature. Voice mail ships as standard with 3Com's NBX 100, Dialogic's IPLink, Ericsson's WS2000, Inter-Tel's AXXESS IP PBX, Avaya/Lucent's Definity and IPExchangeComm, Mitel's Ipera 2000, Shoreline's Communication System (Version 2.0).

With Alcatel's OmniPCX 4400, Cisco's AVVID, NEC's NEAX 2400, Oki Network's IPstage and Vertical Networks' InstantOffice, voice mail is supported either optionally or via a third party add-on or application. Call detail recording, fax, Telephony API messaging and modem support are widely supported. Accounting and billing features are also available, but typically as an option from the IP PBX vendor or via third-party application.

With few exceptions, PC clients are widely supported. These are usually in the form of soft phone software, in which callers use their desktop PCs with microphone/headphone, running a special application, as a regular phone. On Avaya/Lucent's IPExchangeComm, Oki Network's IPstage and TEK Digitel's V-Server OfficeBuilder, client support is limited to support for Microsoft's NetMeeting, one of the most widely used conferencing applications.

In some cases, such as with Alcatel's OmniPCX 4400, Cisco's AVVID, Ericsson's WS2000 and Avaya/Lucent's Definity, PC support comes in the form of a software-based attendant console or other specialized application, such as a call center for bulk call handling and distribution.

Support for IP phones, which are now available with roughly two-thirds of the IP PBX systems, is growing. Half of the products now support an IP phone, and a couple of vendors, such as Shoreline, support an IP phone from a third-party source. IP phones are usually powered via a plug-in AC/DC module for each phone, but several vendors are planning to support in-line power once standards are ratified.

Call-control platforms

Among the "new" IP PBX vendors, Windows NT is the most widely supported platform for call-control and call-routing functions, while established PBX vendors tend to rely on Unix or an embedded operating system. Many of the IP PBXs Mier Communications has tested over the past year were based on NT, and these proved stable and reliable in most instances -- even withstanding heavy call loads for long periods of time. Therefore, it appears that some of the initial reservations expressed about putting critical communications functions on an NT platform are subsiding.

Despite the popularity of NT, today's IP PBXs often support more than one platform, and it is not unusual to find an IP-PBX vendor offer its call-control on NT or Unix. We found only two IP PBXs -- from Cisco and Dialogic -- that support Windows 2000 for call-control and call-routing functions.

Voice-over-IP standards: A moving target

We found that Version 2 of the ITU-T's H.323 standard is the most widely supported voice-over-IP standard today, with 88% of the products supporting it (see Figure 4). However, H.323 does not appear to be the long-term direction of the IP-PBX vendor community. Only 13% of the products currently claim support for H.323 Version 3. This version was ratified in February but is not widely adopted because it's not backward-compatible with previous versions, is complex and difficult to implement. Only about one-fourth of the vendors we interviewed plan to adopt H.323 Version 3 within the near future.

Our survey shows there are too many incompatible voice-over-IP standards. Vendors agree that H.323 is too complex to implement, and many -- including those that now support H.323 -- are looking to other standards, such as Media Gateway Control Protocol (MGCP) and H.248, also known as Media Gateway Control (MEGACO), as the basis for their products' future interoperability.

MGCP and H.248/MEGACO are currently implemented by 31% and 19% of the products, respectively. However, we expect to see more widespread adoption of both of these standards within the next year. Almost half of the vendors we interviewed plan to add MGCP support, and more than one-third said they will add support for H.248/MEGACO in the next year.

MGCP and H.248/MEGACO notwithstanding, the big trend is clearly toward Session Initiation Protocol (SIP), which was published as an Internet draft document last year. While only 13% of the products we surveyed support SIP now, more than two-thirds of the vendors said they will implement SIP over the next year.

Given the turmoil in the voice-over-IP standards arena, it isn't surprising that there is little interoperability among vendors' IP PBX equipment. Even so, several of the vendors we spoke to indicate that interoperability is a big user concern, and some positive movement toward interoperability is slowly happening.

3Com's NBX 100, an early IP PBX market leader, interoperates with a number of other vendors' products, including Elemedia/Lucent's H.323 gateways; Apropos' Total Interaction Management Call Center and Symbol IP phones.

According to Hank Lambert, Cisco's manager of IP telephony infrastructure, Cisco supports all the voice-over-IP standards mentioned so far, providing bridges among all the different installed bases. Cisco says it also interoperates with Symbol Wireless Phones and Microsoft NetMeeting.

Management and monitoring

A majority of the IP PBXs surveyed support a Web browser-based management interface, often in addition to a Windows-based application. SNMP is supported on 75% of the products, but in some cases this is limited to general system monitoring.

More than half of the vendors said they supported a mix of real-time status monitoring of analog/digital trunks; IP bandwidth utilization; number of calls in progress; relative quality of IP network transport; and voice-mail storage capacity.

How the vendors handle event logging and reporting -- the key components of fault management -- varied.

On the NBX 100, 3Com maintains two logs: One captures a record of administrative changes; the other captures warnings and errors. Both can be viewed via a Web-based interface.

Ericsson's WS2000 Version 2.5 supports event reporting on hardware and software failures, as well as any subsystem event.

On Avaya/Lucent's Definity, monitoring is SNMP-based, including fault and traffic analysis, long-term reporting of alarms, trunks, stations, configuration and inventory.

Vertical Networks' InstantOffice supports a "trace manager" -- a complete system activity log that reports calls in progress in real time; abnormal events are flagged and traps and alarms are issued accordingly. InstantOffice also supports an independent fault monitor.

Shoreline integrates its event logging, alerting and warnings into the NT event log, viewable via a Web browser and with customizable event filters. Severe alerts can trigger an e-mail to a specific technical-support employee.

Pricing trends

Average prices for IP PBXs are about $50,000 for a 100-station system -- or about $500 per port -- in configurations supporting IP and/or analog station ports, one T-1 trunk or 24 analog trunks, voice-over-IP support and management. Vertical Networks' InstantOffice was the least-expensive product in our survey ringing in at $331 per station. Alcatel's OmniPCX 4400 weighs in on the high end -- nearly $1,000 per station -- depending on the type of handsets and features supported for 100 station ports. The high-end price includes voice mail.

Vendors with low-end IP PBXs, supporting fewer than 50 stations, are developing relationships with service providers to penetrate new markets.

Tek Digital's V-Server OfficeBuilder, which costs $1,699, is being sold primarily to service providers that bundle the product into their service offerings. The service providers make their money on the monthly service charges -- not through the sale of OfficeBuilder.

Market directions

IP PBX vendors are understandably upbeat about the future. Most see the installed base at least doubling within the next three to four months. Others predict that more than 10% of all PBX ports installed within the next three years will be IP ports.

"The market is not just experimental anymore. It's becoming practical," says Bo Larsson, senior vice president of Ericsson's Enterprise systems. Larsson says telecommuting, particularly in high-end campus environments, is driving sales of Ericsson's WS2000 (formerly the WebSwitch).

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