IP-Centrex—Prospects and Pilot Trials

IP-Centrex—Prospects and Pilot Trials
Because relatively few organizations have implemented IP-Centrex on a commercial basis and many telecom service providers work in a highly competitive environment, it has been a challenge to obtain information about appropriate case studies. The situation of a large Centrex customer, which participated in a limited IP-Centrex technology trial, is then described in some detail. Finally, we include descriptions of several IP-Centrex trials for which some information has been made available.

IP-Centrex Prospects

A municipal government that serves a city of over 250,000 people has 900 full-time employees supported by Centrex in 70 locations, some of which are indicated in the map in Figure 1. The city's Works Department has a fairly modern 120-station PBX, rather than using Centrex, because it is located outside the serving area of the main Centrex-providing CO. The municipality's Centrex service contract is approaching the end of its 10-year term, during which it has provided each line at an attractive 50% discount off the current rate. A new Centrex contract would look expensive to the city because of structural changes in the tariff within recent years. The CIO of this city, therefore, faces a dilemma regarding the annual telephone service bill of $300,000, with the choice of moving to a network of conventional PBX systems, investing in anew IP-PBX infrastructure, or hoping to use IP-Centrex as being suited to an organization with many small offices. There is a serious drawback with each alternative as the system vendors wind down the development of circuit-switched PBXs; the technology of IP-PBXs seems not yet to be settled and the local ILEC cannot offer a schedule for IP-Centrex availability.

Figure 1: Municipal locations.

The city owns an optical fiber network that can be linked into locations housing 90% of its personnel. This fiber is installed in ducts that were primarily used for the copper cables linking traffic lights to the traffic control computer center.

Probably the best solution is to negotiate a 1-year extension to the present Centrex contract and hope that the options become more clearly defined meanwhile.

A newly organized health care corporation needs to integrate the services of four hospitals, located as on the map in Figure 2. The hospitals and associated clinics employ about 1,500 phones and 50 fax machines. One-third of the phones are single-line, analog sets and are in patients' rooms. The largest hospital in this group, with about 50% of the lines, has a seriously out-of-date PBX and overloaded voice mail/autoattendant subsystem. A major objective is to present a single image to the public served by the health care corporation, as each site will concentrate on selected specializations to achieve optimum economies of scale.

Figure 2: Healthcare network integrates four hospitals.

The corporation's board also intends to implement video communications extensively, within a short time frame, to minimize travel time and expenses, for both professional staff and patients. IP-compatible video-conferencing units from several well-established vendors are now available at very competitive prices.

Because this health care organization is in a small, rural town, beyond commuting distance from a large city, it has great difficulty in recruiting and retaining well-trained telecom professionals. Additionally, this market area is not yet attractive to competitive broadband network providers. A deployment strategy that uses IP-Centrex at the largest hospital and integrates three existing small-to-medium PBXs into the corporate network with IP trunk gateway cards is probably the best solution. TI links leased from the telco will serve sites W and E, while the smaller hospital at N will have frame-relay data service at a fractional TI bit rate.

A solo consultant has been a small Centrex customer for 10 years, working from his home office. The positive side of small Centrex is that lots of features (including calling line ID and three-party conference calling) are bundled into the service with no extra costs, at a rental not much above that for a basic business line. The negatives are that there have been no service improvements for a decade, the service is not well marketed, and no one at the local telco's office is willing to talk about small Centrex. The service provider has, obviously, not tried to mine its customer database or to get new services out to these small businesses. Additionally, this customer has not received one sales pitch from any Centrex reseller, in the last 10 years, to sell competitive services. Another concern is that the electronic business set (EBS), which has digital signaling, uses local ac power and is not on during a power failure.

To provide for good service quality, this small office requires two Centrex lines and needs three "PSTN accesses" so that two calls can be handled simultaneously and a third call can be diverted to voice mail. One of the two physical Centrex lines is defined as analog, to serve a fax machine, and that line is also used for ADSL, providing high-speed Internet access. The total monthly rental for two Centrex lines and three network accesses (not including the ADSL service) is about $80.

Since there are no restrictions on access to competitive services, the consultant rents unified messaging from Sprint (at approximately $10 monthly for 200 minutes of storage), because a single voice mailbox is provided for calls to the Centrex wireline phones and to a cell phone. The ILEC, which provides the small Centrex, has configured its own voice mail service in a way that does not allow call forwarding from any number other than the Centrex line. This customer has installed a total of six outlets in his house, so that he can move phones, fax, or modem around without paying any relocation fees.

For small and home office (SOHO) users, the prospects with IP-Centrex are as follows:

- All services will use one DSL access line.

- Some Computer Telephony Integration (CTI) functionality, such as the availability of an on-line dialing list, will be available.

- Programmable IP telephones that receive DC power over the wires from the CO will be sold at reasonable prices.

- Integrated UM service will be accessible from a cell phone, or other mobile devices, in most locations, if served by a digital radio network


Concerns with IP-PBXs

Concerns with IP-PBXs
We have a number of concerns with IP-PBXs that are specific to these systems and are not identified, as applicable to IP-Centrex. Some of the following considerations may be sorted out over time, but the last four in the list will probably stay with us for years to come:

- The capital cost of an IP-PBX is still likely to be higher than that of a TDM-based PBX with a similar capacity. In most price quotations that we saw in 2001, the IP-PBX vendor was asking an average of 30% more than for the traditional PBX. By the end of 2004 there will, probably, not be any difference in pricing between the two architectures.

- On the other hand, the manufacturer-supported life of a conventional PBX will probably be limited, as development funds are dedicated to the IP-based systems.

- Several IP-PBX vendors have launched their product and then changed their plans within a year or two. Additionally, every system includes some proprietary features that make the free interchange of components, such as phones and gateways, difficult.

- Many of the interesting applications that have been promised with IP telephony have not yet been written, or may exist only for one specific combination of telephone and computer systems.

- Several manufacturers, such as Alcatel and Mitel, have based their main IP-PBX on a dual-switching fabric architecture, retaining a TDM capability in the same box as an IP-oriented call controller. This complexity must add cost to the system and make fault diagnosis and maintenance more difficult.

- For these reasons, this approach may not be the best long-term investment for the customer. It may be a better strategy to acquire a pure, IP-only system and to support non-IP phones by outboard gateways, which could be moved to other locations as conversions proceed. Because of its complexity, a hybrid TDM/IP system is probably not the right vehicle on which to base an out-sourced IP telephony service.

- The integration of voice, video, and data signals over an IP network demands a special set of design and implementation skills, which take time and practical experience to acquire.

- One of the advantages claimed for IP telephony is the cost savings that results from using one system management package instead of two. However, telephony and video conferencing are not just two more applications that will now reside on the corporate LAN. There is a serious risk when management becomes convinced that anyone with some data expertise can plan, configure, and administer a feature-rich, multimedia system. Because organizations still depend on voice communications with their customers and prospects, they cannot afford to eliminate voice system administration expertise entirely.

Most of the early installations of IP-PBXs were treated as pilot trials, in conjunction with larger, legacy digital systems. The integration of IP phones into the existing voice mail subsystem and with the number display features of the TDM-based PBX proved difficult and remains insoluble in some cases.

Several small office-in-one-box products, including those from Cisco and Mitel, have come onto the market as part of the development of IP-PBXs. We should remember that some major manufacturers, including Nortel and Wang, launched integrated small office systems (at that time including a built-in 3270 controller for IBM mainframe terminals) in the mid-1980s, and that all of these products were dramatic failures. Most organizations have long since decided which manufacturer's data equipment is to be used in their networks and probably are not prepared to change at this stage.

Because Cisco controls some 80% of the enterprise-level data network equipment market, the company dominates its accounts, in the same way that IBM was all-powerful in the data processing business of the 1960s and 1970s. Some decisions to buy an IP-PBX were made by the CIO or another senior manager because of this influence, sometimes against the advice of the company's telecom manager.


Advantages of IP-PBXs

Advantages of IP-PBXs
The relative importance of the advantages that are claimed for IP-PBXs (as compared with legacy digital PBXs) has changed since these systems first appeared in 1997, but the claims are now fairly consistent among the IP-PBX vendors. The positive aspects of IP-PBXs can be summarized in the following points:

- Use the same Ethernet networks for all forms of telecommunications. This immediately means eliminating the need for separate data and voice cabling installations and, ultimately, for any voice-only wide area connections.

- Simplify the MAC tasks, since an IP phone, with its built-in intelligence, can be plugged into any outlet on the corporate network. Some early adopters of an IP-PBX claim that up to 50% of MACs can be done by users, without the involvement of any telecom professional.

- Use a Web-based browser management package to administer the features and configuration of an integrated voice, video, and data network, from anywhere that has network access. The administration of the corporate telephone system now becomes a function of the IT department, which already has the required data networking expertise.

- Gain access to existing and new applications that run on the organization's network, through an IP phone. Some users may not have access to a desktop PC and others may find it simpler to use a phone rather than a computer. One major law firm, for example, claims that it fully cost-justified its purchase of an IP-PBX because its lawyers were then able simply to use an on-line time-tracking package and bill its clients for more hours in a week.

- Carry intersite voice and video traffic over the corporate data network, and thus do not spend money on long-distance charges that apply to the PSTN.

- Have a centralized, reliable call-processing server, which is the core of the IP-PBX, but do not need to deploy other voice switches at the remote, smaller corporate locations. Since the signal transport cost across an intranet is low, the intelligence can be in one place, even as the packet switches are distributed, and considerable expenditure can be saved.

- An integrated messaging server that is based on industry-standard protocols and processors delivers more storage at much less cost than a proprietary voice mail system.

The issue of replacing TDM-based PBXs, or legacy Centrex, with an IP-PBX is not nearly as clear-cut as these seven advantages might suggest. We can find at least one counterargument to each of these points. For instance, the toll bypass justification for VoIP is not now nearly as powerful as once it was.

The fall-off in PBX sales over the past few years has been partly caused by the economic slowdown, but undoubtedly also results from uncertainty regarding the viability of IP-PBXs and their place in corporate plans.


Current IP-PBX System : Siemens

Siemens purchased three major PBX makers, based in the United States, Belgium, and Britain, during the early 1990s and so has the largest share of the worldwide installed base of PBX systems. The company also claims to have sold more digital CO ports, at well over 100 million, on its EWSD system than any other telecom manufacturer.

For small and medium-sized enterprises, Siemens offers the HiPath 3000 family of IP platforms, with the user capacities that are stated in Figure 1. These systems can be linked in an IP-based network with the AllServe 150 applications processor, to support up to 1,000 users.

Figure 1: Capacity of HiPath 3000 call servers.

Each of these call servers is available in a 19-inch rack-mounting form (the 3300) or as a cabinet, which is wall-mounting (3550) or floor-standing (the HiPath 3750). For markets with European ISDN standards, Siemens also supplies two smaller systems, which are not strictly IP-PBXs: the HiPath 3150, for up to 14 users, and the HiPath 3250, with two basic rate interface (BRI) ports.

In association with its HiPath systems, Siemens introduced a range of optiPoint 500 phones, replacing the optiPoint 300 sets, which had garnered praise for their ergonomic qualities but could not support in-line dc power over the LAN. Five optiPoint 500 IP telephones are available, ranging from an entry model to the advanced, of which three have a Universal Serial Bus (USB) interface, while four models have a display and loudspeaker. Additionally, the optiPoint 400 phones are multiprotocol sets designed for platform and location independence, while still having a built-in Ethernet interface and power-over-LAN capability.

The Siemens CorNet package facilitates networking over an IP WAN, or the PSTN with the more powerful HiPath 4000 or 5000 platforms, and Siemens emphasizes that applications need only be installed once to be accessible across the entire company and from every workstation. Under the HiPath brand name are Xpression for unified messaging, ProCenter for multimedia contact centers, and Fault Management software.

The HiPath 4000 is an IP convergence platform, available in three models, that supports up to 30,000 users on the largest system. The HiPath 5000 is a pure IP communications system, to which all the features and functions of the Siemens' HiCom300 PBX have been transferred, and which can be installed on industry-standard servers running Microsoft Windows NT or Windows 2000.

Siemens deployed its HiPath 5000 system to support over 1,000 IP phones and soft clients in its new San Jose, California, facility during 2000. A detailed diagram, showing how many of Siemens' IP telephony products may be used, is shown in Figure 2.

Figure 2: Siemens' HiPath systems and terminals.

The RG 2500 is a VoIP gateway that transforms voice signals into IP packets (or vice versa). The optiClient 330 is a PC-based soft client, using the Windows format. The HiPath AP 1100 and 1140 provide analog ports on the line side. The PhoneMail system is a high-performance voice mail product that was inherited by Siemens from ROLM via IBM.


Current IP-PBX system : Nortel Networks

Nortel Networks
Nortel Networks claims that it is the only telecom equipment supplier to "remain in both camps," believing that it is absolutely necessary to give the customer the choice between a TDM-based PBX, for the lowest single site costs, and an IP-PBX, where that may make sense.

Nortel is certainly the leader in providing IP-enabled telephony, through an Internet Telephony Gateway (ITG) Trunk card, which plugs into a Meridian 1 PBX and may be programmed to support trunks with an IP-network. Another version of this ITG can have up to 96 users connected to one card on the line side, so that the capacity of Nortel's Meridian Option 81C can go up to 16,000 IP phones. Nortel's ITG Line Card actually has 24 DSP ports.

Most of Nortel's large PBX customers have implemented these ITG cards to carry voice traffic over IP long-haul networks, and this was an excellent way for these organizations to gain VoIP expertise. Microsoft Corporation, for example, connected 87 Meridian 1 PBXs over its IP-VPN and recovered the cost of these ITG installations, with long-distance savings, in less than 6 months.

Nortel offers two remote office units, the models 9110 and 9150, which support IP phones, but overcome the problems of local calling and emergency 911 requirements by using BRI/ISDN trunks. These units have a key capability of dynamic fallback, even during a conversation, between an IP network and the PSTN. If the trunk channel over the customer's IP-VPN fails or degrades badly, the call is switched to the PSTN, but it can return automatically to the IP network upon restoration of service, saving the customer money.

A variety of client endpoints is available for VoIP use. Nortel has two IP phones (the i2004 and i2002), the i2050 softphone, software to make the Palm Pilot SIP-enabled, wireless phones made by Symbol, and an IP-adapter base for the 39xx series of digital sets. If a Nortel IP phone and a PC are to share one LAN outlet, then a three-port switch adapter base for the i series phones must be purchased. The use of these peripherals in a CSE 1000 configuration is shown in Figure 1. Nortel reports that some early IP telephony installations used a dedicated LAN, with no data traffic on the same wiring.

Figure 1: Succession CSE 1000 configuration.

Previously existing subsystems for unified messaging (Call Pilot), contact centers (Symposium), and system management (Optivity) have been adapted to interface with the CSE 1000, which is Nortel's enterprise-level, IP-oriented call server, using the brand name Succession. One CSE 1000 can handle up to 1,000 users and at least 10 servers may be in one network. This server uses the same UNIX-like operating system as Nortel's smaller TDM PBX, the option 11C system, so that it was fairly easy to transfer all 450 telephony features to a pure IP architecture.

The Succession Media Gateway, the unit that provides links to WANs, uses TDM trunk cards that are the same as those purchased for legacy Meridian PBXs, delivering a major cost saving to customers. This media gateway has some local call processing capability and is, therefore, useful for remote locations to provide service survivability.

Nortel's multimedia exchange system, the CSE-MX, is a good example of the benefits that come with IP telephony and new protocols, such as SIP. The CSE-MX is a multimedia application server, which facilitates video conferencing and instant messaging within an enterprise network. With multimedia services the setup of a multiparty video conference, between preregistered participants, should be feasible with a few mouse clicks, and collaborative working between remote offices is greatly improved by the sharing of Web sites, files, visuals, and electronic whiteboard.

The CSE-MX also supports dynamic registration (i.e., "find-me and follow-me" service) for mobile and telecommuting users, and provides a personal call agent. This function can be used for call screening and call routing to user-defined locations, which should result in the need to process fewer voice and electronic mail messages.


Current IP-PBX system : NEC

NEC has grown to be a corporate giant while, unlike most of its competitors, keeping the same name for over a century. Within a wide range of telecommunications and electronics products, NEC is a major force in PBX and CO systems. The company is the third-largest supplier of enterprise voice switches in the United States, conducting the development of its PBX systems in Dallas, Texas.

NEC sells three sizes of PBX systems, ranging from the NEAX 1000 through the 2000 and the 2400. Of particular interest with IP telephony developments are the NEAX 2000 Express, 2000 IPS, and the 2400 IPX.

The NEAX Express was one of the first IP-oriented PBXs to be announced by a legacy PBX maker and is based on a unique design. NEC took a different approach by compressing its existing NEAX 2000 into a few circuit cards and sharing one chassis, with a common power supply, between the small PBX and three cards that operate as a standard Windows NT server. This approach is shown in Figure 1.

Figure 1: NEAX 2000 Express system.

This configuration provides IP communications to Microsoft BackOffice Server, with computer-telephony integration, so that voice mail, autoattendant, and unified messaging can be delivered to small and branch office environments. Third-party developed applications, such as ACD and Interactive Voice Response (IVR), can also run in the NT-based server. The basic model of the NEAX Express supports 36 digital and 8 analog stations, but can be expanded to 100 users. It employs the reliable voice-switching matrix from the widely used NEAX 2000 and, while it can deliver the applications promised for IP telephony, does not have interfaces for IP phones or to IP WANs.

NEC launched its NEAX 2000 Internet Protocol Server (IPS) at the end of 2001 as a medium-sized product that is complementary to the NEAX 2400. The 2000 IPS includes both packet and circuit switching in the same system and can be configured in any mix from all TDMs to 100% IP telephony, with up to 500 stations.

Rather than producing a series of IP telephones, NEC sells an IPW-2U adapter, which fits into the bottom of its digital Dterm series E phones. This IP enabler dynamically acquires all the information it needs to interoperate with a NEAX IPS or IPX.

The NEAX 2400 IPX is a version of NEC's large PBX that supports IP telephony on the trunk and line sides, while retaining its standard switching fabric. This IP-enabled PBX can be closely integrated in a network with the NEAX Express or 2000 IPS, as well as with earlier 2400 ICS. This architecture allows customers to migrate to IP telephony, whether they have a new or an upgraded system.

The NEAX 2400 has been on the market through various developments for nearly 20 years and is a powerful PBX with distributed control processing that can have up to 24,000 lines on one system. This PBX has excellent ACD functionality and has achieved a reputation for reliability, as shown by its widespread use in hospitals and military bases.


Current IP-PBX Systems: Verizon ; C & W ; Mitel Networks

Verizon, in the United States, will help customers avoid implementation difficulties by providing up-front network and physical site assessments that will identify potential migration pitfalls and pinpoint data network equipment that requires upgrading to handle voice traffic. Verizon will also do comprehensive planning to develop the processes and procedures necessary for successful convergence of their customers' multiple networks.

Cisco and Verizon also joined forces to market high-speed, secure, and reliable work-at-home services, over an IP-enabled network, for advanced teleworker programs. This offering certainly sounds as though it involves IP-Centrex.

C & W
C&W, with its Convergence PBX solution, can deliver IP-PBX, IP-LAN, and IP-VPN services to medium and large-sized businesses on a global basis.

The first major customer for C&W's Cisco-powered network was the well-known Marks & Spencer retailer, with over 300 stores in the United Kingdom. C & W has a private MPLS-IP network, which will be dedicated to voice, video, and data traffic from its Convergence PBX customers, and can deliver customized QoS parameters to national or international users.

Mitel Networks
Mitel Networks, now a private company owned by one of its original founders, uniquely concentrates on the enterprise voice communications system market. Since it was started in the mid-l970s, Mitel has been sold several times, but has managed to survive and attract the appropriate talent to move confidently into the IP telephony era.

Mitel has always manufactured several models of PBX and for many years had an especially good reputation with reliable telephone systems for small businesses. The company claims that it will continue to develop its SX-200 and SX-2000 TDM-based PBXs, while putting a lot of effort into two IP-oriented systems.

Mitel introduced its 3100 Integrated Communications Platform (ICP), which was designed and is manufactured in Britain, in late 2001. This small, rack-mounting system combines a complete set of voice features, including integrated voice mail and autoattendant, a 10/100Mbps Ethernet LAN switch, and a router. The voice switch may be configured as a PBX, a key telephone system (KTS), or a hybrid, supporting up to 24 IP phones and 10 analog stations (with an extension module). Up to 100 IP addresses are available with the 3100 ICP, so some 75 data devices, such as PCs, printers, or servers, could be attached. The 3100 ICP is intended for stand-alone offices or similar locations, but cannot be used as a satellite system in a tightly coupled corporate network based on Mitel's more powerful call servers.

Mitel's 3300 ICP is intended for medium-to-large organizations, while inheriting all of the telephony features and networking capabilities of the SX-2000 digital PBX (which was first launched 20 years ago), for up to 700 users from one call server. The rack-mounting call controller is complemented by an analog services unit (for lines and trunks) and a network services unit (for up to 16 T1/E1 or ISDN/PRI links). A Mitel 3300 configuration is shown in Figure 4.4, with a model 3340 ICP serving a remote location and IP stations in a small remote office connected directly to the network.

Figure 1: Converged communications in the enterprise by Mitel.

Although Figure 1 shows only IP phones, the 3300 ICP does include a TDM switching bus, so that it can support Mitel's preexisting digital phones through direct single-pair wiring. This Mitel system works with any of the commonly available data switches in the networking market, although the initial versions of Mitel's IP phones used a proprietary protocol.

The 3300 ICP has embedded voice mail, with just a nominal charge for user licenses with the first 20 DSP ports, and this system has full autoattendant features. Mitel sells the model 6500 speech-enabled attendant, which includes toll fraud prevention and mobility features, for forwarding calls to variety of numbers, based on a preset schedule. The 6500 package also provides natural speech navigation of its unified messaging function that may be integrated with Microsoft Outlook.

An easy-to-use system management subsystem, with different sets of tools for system configuration, administration, and simple moves and changes, is also supplied as part of Mitel's 3300.


Current IP-PBX Systems: Cisco Systems

Cisco Systems
Cisco Systems cannot claim to have invented IP-PBXs, but it certainly established the market for these systems by making IP telephony legitimate. Cisco's IP-based system is known as the Architecture for Voice, Video and Integrated Data (AVVID), and this product started shipping in mid-2000. Two years later Cisco claimed to have shipped 800,000 IP phones and, more impressively, to have equipped 6 million ports with power for IP phones.

Cisco's CallManager is the software-based call processing component of the IP telephony solution, extending features and functions to packet telephony devices such as IP phones, multimedia applications, and VoIP gateways. Additional data, voice, and video services, such as integrated messaging (the Unity product), multimedia conferencing, collaborative contact centers, and interactive response systems, may be linked with the IP-PBX through an open telephony API.

Cisco's CallManager is installed on a media convergence server (in the MCS 78xx series), which is a standard computer from manufacturers such as HP-Compaq, Dell, or IBM, with the exact specification set by Cisco and absolutely no applications other than telephony running in the MCS. Release 4.0 of CallManager can support up to 50,000 users and a conceptual network, with multiple voice servers, as illustrated in Figure 4.3. This software release also supports SIP, but Cisco believes that media gateway control protocol (MGCP) will be the protocol of choice within an enterprise for IP telephony.

Figure 1: Cisco CallManager clustering.

Concerns about availability and reliability are addressed by using multiple servers, which may not be in the same location, and by having dual gateways to the WAN, which is not shown in Figure 1.

While the typical IP-PBX configuration is deconstructed into multiple components (communications server, LAN switch, trunk gateway to the PSTN, line gateways for digital and analog phones, and router to the IP-WAN), Cisco does have an all-in-one-box chassis-based CallManager 7750 system, for branch offices with from 50 to 250 users. There is also a 4225 system, for up to 20 users, serving phones and PCs, with a built-in data switch and router.

Cisco sells a number of models of desktop telephones—including the 7960 (6 lines), 7940 (4 lines), and 7910 (single line), together with an IP conference phone that was developed jointly with Polycom. Each of these phones includes a three-way switch, for 10- or 100-Mbps Ethernet connections, and can be dc-powered over the LAN from a Cisco distribution unit, situated in a telecom closet. The softphone product is good for collaborative working between PC users. Cisco was expected to have its own wireless phone, designed for the IEEE 802.11a standard, on the market in 2003, while wireless phones from Spectralink and Symbol, working to the 802.1 1b protocol, may be used with AWID.

For users to do their own system administration, such as call routing and screening, Cisco's Personal Assistant has speech recognition navigation with all its options linked to the class of service established for each user. Since an IP phone may be moved to any corporate network outlet, a report sponsored by Cisco and published by the Telecom Applications Research Alliance (TARA), in the spring of 2000 optimistically claimed that "the effort required for Moves, Adds and Changes is only 25% of that typical for a PBX of the same size."

We should note that Cisco's Unity voice mail system can connect simultaneously to CallManager and to legacy PBXs. On the other hand, it is still difficult to integrate between Unity and existing voice mail systems, so owners of Meridian Mail and Octel systems will need to replace these with the Cisco product, in those configurations where CallManager has been installed with TDM PBXs.

Cisco's well-known CEO, John Chambers, has been quoted as saying, "Data-voice-video integration is huge for us because it forces my customers to redo their networks," and this certainly appears to be coming true.

Cisco has signed agreements with several large service providers to support convergence of multiple networks with the AVVID solution, even while the users retain ownership of their systems. These situations may be classified as managed IP-PBXs and managed IP-Networks, but will not be the same as IP-Centrex.


Current IP-PBX Systems: Avaya

Avaya was spun off from Lucent Technologies in the year 2000, so that the company now provides voice and data network products primarily for enterprise customers. Through its acquisition of Octel, Avaya is the world's largest supplier of voice mail systems.

When the early IP-PBXs first came onto the market, from data switch suppliers, Avaya appeared officially to denigrate these products and to emphasize the power of its Definity systems. After a period of uncertainty about its direction, the company now describes the migration to IP telephony as being "an imperative and a necessary strategy for business."

Avaya introduced a family of media servers and gateways in mid-2002, as its second generation of IP telephony systems, under the name Enterprise Class IP Solutions (ECLIPS). All the features of the Definity range of PBXs and contact center functions are implemented with MultiVantage software that runs in these servers. Some of the capabilities of the three media servers are summarized in Table 1.

Avaya defines the call processing power of its systems by the number of busy hour call completions (BHCC), which very much depends on the complexity of the processing for each call. For this reason the BHCC number is lower by a factor of two-fifths for contact center calls than for the general mix of calls.

Avaya sells three different softphone packages—one for a desktop or laptop PC, another for pocket PCs that use Windows CE software, and also the IP Agent, which is intended for contact center personnel. There are five IP phones in Avaya's 46xx range, all with built-in speakerphone and power over the LAN technology. The most expensive model has a full-color, touch-sensitive screen for Web access browsing and six integrated telephony-related applications. A three-port switch base is available for three of the Avaya IP phones, so that a PC can share one LAN outlet with the desktop phone. All of these phones, except the basic model, have an infrared port for communication with a PC or PDA.

Avaya has developed its reputation as North America's leading supplier in of call center solutions, which are integrated with the Definity PBXs. The company now sells a multimedia contact center system that can interwork with several other major PBX and IVR systems. The modular architecture of Avaya's Interaction Center software provides for the management of voice calls, e-mail, Web-based interaction, and contact center agents, while providing computer telephony integration to the three most commonly used database systems.

Avaya supplied 25 ECLIPS servers to the month-long World Cup of football/soccer to connect 7,000 voice endpoints in Japan and South Korea. The IP WAN for this event successfully carried about 100,000 phone calls each day, in addition to conventional data traffic, thus proving the viability of the mass adoption of Internet telephony.


Current IP-PBX Systems: Alcatel

The IP-PBXs that are on the world's enterprise marketplace come from a variety of backgrounds and include at least one model in each of the three classes that are defined here. We include reviews of IP-PBXs from eight suppliers, which sell their systems in many countries. Since it is too early in the development of these products to decide which are winners or losers, we have focused on the different approaches taken by the manufacturers, while not attempting to describe each system in great detail. These reviews are listed by alphabetical order of the manufacturer's name.

Alcatel introduced its OmniPCX 4400 in 1996, as a call server that handles TDM and IP user terminals, with the same services, set of features, and standards of reliability of other digital PBXs. The 4400 is available in four cabinet sizes, as follows:

- Media Gateway (rack-mounted) for up to 64 users;

- WM1 (wall-mounted) for up to 150 users;

- M2 (floor-standing) for 100 to 400 users;

- M3 (three cabinets) for up to 1,000 users.

One hundred OmniPCX nodes can be connected into a network, supporting up to 50,000 stations. The network may be based on TDM trunks or packet (ATM, frame relay or IP) transmission technologies. The architecture of this system is illustrated in Figure 1.

Figure 1: Architecture of Alcatel's OmniPCX 4400.

The PWT 4073 handset uses Alcatel's Private Wireless Telecommunications cellular technology, which is designed for higher user density environments, with up to 10,000 Erlangs per square kilometer. One PCX 4400 server can be linked to 256 base stations and 1,000 wireless users.

Alcatel sells four proprietary telephones (under the trade name Reflexes) which are all digital sets with a display. The Advantage 4035 and Premium 4020 models have an integrated alphabetic keyboard and can include a built-in IP enabler. The more recent version of this module has a 10/100 Mbps Ethernet interface and a mini-LAN switch function, for an adjunct desktop PC connection (so that a desktop PC may be connected into this module, enabling a telephone and the PC to share one LAN outlet). The integrated IP enabler can be fed with DC power remotely, from an OmniPower Patch Panel that operates to the IEEE 802.3AF standard. These two phones show the design influence of the Minitel terminals that were extensively used on France's information network prior to the Internet, but are likely to be relatively expensive when equipped for IP operation. For the two lower-cost phones to be used in the IP mode an external IP enabler is needed.

Alcatel also has a suite of contact center applications, known as OmniTouch, which is integrated with the 4400 system. The agents' stations may be based on the model 4004 or 4035 phones, or may use the Alcatel4980 telephony application that runs on a PC, providing groupware and call management functions.

With this hybrid voice communications system, Alcatel has returned to the crowded North American market, where one of its predecessor companies, IT&T, once had a presence. Alcatel has gained some good PBX accounts in the United States with the OmniPCX 4400, displacing Centrex service in a few cases, and it is obtaining significant dealer support in Canada. In some Latin American countries Alcatel has achieved a major share of the PBX and CO systems markets, displacing Ericsson over the past decade. The company also has a strong presence in the data switch, network management, and VPN businesses through its acquisition of Newbridge Networks.

At the time of this writing, no news of contracts to use the OmniPCX 4400 for managed IP-PBX or IP-Centrex services has been released. Even though this is now a well-established product, it might not be the most attractive vehicle to outsourcing service providers


Broadband Availability

Broadband Availability
For some years the telecommunications industry has worked hard on various methods to provide high-capacity access to the Internet. The result of this heavy investment (some of which is less valuable now than its original cost) is generally a competitive environment of broadband access availability.

We can identify seven ways to obtain broadband connectivity (that is, appropriate for business VoIP applications) between on-premise LANs and managed WANs, as follows:

Leased digital links using legacy TDM technology are available as DS-1 (i.e., "Tl" as it is commonly known) at 1.5 Mbps, or DS-3, at 45 Mbps. Outside North America the equivalent multichannel digital services are El (at 2 Mbps) and E3 (at 34 Mbps). With the tariffs charged by the incumbent telcos these services are not attractive, but under competitive conditions may still have a role to play.

Switched ISDN channels are at basic (144 Kbps) or primary (1.5 or 2 Mbps) rates. ISDN-PRI was widely used in the early years of rapid growth with the ISP business but, again, is not now competitively priced in most areas.

DSL services are widely offered in many countries at attractive prices.

Cable modems (CMs) are linked by hybrid coaxial/optical fiber to the two-way network of the local monopoly cable TV carrier.

Digital cellular wireless services have moved into the 2.5G and 3G developments. These services have the advantage of mobility and may also be of limited usefulness for fixed locations.

Microwave radio services for broadband access are primarily of the point-to-multipoint type. These high-frequency technologies, such as local multipoint distribution services (LMDS), generated considerable interest when licenses were sold in the mid-1990s. Unfortunately, most of the new fixed-broadband radio carriers have collapsed financially and this choice is not widely available.

Extended Ethernet
(i.e., native IP transmission) over optical fiber is available in many urban areas from multiple service providers.

We should note that "sky-based" communications services, whether from geostationary or low-earth-orbit satellites, are not suitable for any interactive VoIP applications, because of either significant transit delays or serious unbalance between the up and down-link data rates.

One major advantage that will become obvious with IP-Centrex is that customers can afford to rent a second broadband access link to their main locations, providing better availability of service than was feasible with legacy Centrex. On a fair accounting basis, the true cost of the copper wire component of a local loop (the traditional "last mile") is around $10 per month. The actual cost of local access bandwidth to support one IP-Centrex user, in a medium-sized office of 100 users, will be less than one-half of that amount. This leaves an ample margin to pay for a second access link, perhaps at a degraded bit rate, that is both physically and service-provider redundant.

Four of the service types that are summarized in the following sections are worthy of further consideration.

DSL Services
DSL services use up to several megahertz of bandwidth over the local loop, compared with conventional, single-carrier modems, which are restricted to the 3.4 kHz that is generally available for audio telephone signals. This means that DSL signals cannot pass through any switch (i.e., PBX or CO) and, because of high attenuation at the higher frequencies, the usable range is limited to a few miles over the standard 24 American Wire Gauge (AWG) copper wire.

In the customer's premises the DSL modem provides an Ethernet interface to the internal LAN, while at the serving carrier's site the DSL terminates on a digital subscriber line access multiplexer (DSLAM), which is linked directly to the IP or ATM WAN on the trunk side. With ADSL service, an analog channel is reserved for one conventional telephone line, below the frequencies employed for the DSL. But in a fully IP, packet-only access environment, which we can call the all-digital loop (ADL), the full bandwidth over the copper wires can be exploited and there is no need for frequency splitters at each end, resulting in lower equipment costs. This is illustrated in Figure 1 for the home office situation, to which dc power can be sent for the phones, because of the end-to-end copper loop.

Figure1:All-digital loop architecture.

Most DSL customers are currently using the service for Internet access from their homes and small businesses. In North America, in late 2002, there were about 4 million DSL users, compared with 7 million cable modem subscribers. In Britain and several other Western European countries, the adoption of DSL remained extremely low, because the incumbents were slow to "unbundle" local loops to competitive carriers and prices were kept too high. By contrast, in South Korea over 10 million customers use a DSL connection for Internet access.

We expect that monthly prices for ADSL will settle in the $30 to $SO range, with HDSL at less than $200, and that DSL will be, by far, the most common broadband access service for small offices, such as bank branches, medical clinics, and schools.

Cable Modems

Cable modems, which use the cable TV infrastructure to deliver broadband access, quickly became popular in North America and Western Europe, where there is a fairly high residential cable penetration, with prices of around $30 per month for nominal 6-Mbps service. Some cable carriers also offer a 128-Kbps access service at a lower cost (e.g., $18 per month) to compete with dial-up modems.

For business applications, such as IP-Centrex, CM for broadband access has two serious disadvantages:

- Cable TV is a shared service (like an extended, single-cable, LAN), with the worrisome implications of security risk and variable throughput.

- The typical cable TV operating company does not share the same sense of service reliability as an incumbent telco.

Next Generation Wireless Services
Next generation wireless services deliver data transmission rates over the digital cellular (or PCS) networks that are similar to those at the low end of wireline capabilities. For IP-Centrex applications these wireless networks primarily serve mobile users and can be valuable as "fixed mode cellular," providing local access redundancy for small offices. For example, it may be worth spending a few extra dollars for a wireless data service to back up a cable connection to a home office.

The so-called 2.5G data capability is now widely available with digital cellular services in two versions. The general packet radio service (GPRS) is an option with GSM that can deliver a data rate of up to 56 Kbps. With the CDMA services, mainly in North America, the clumsily named one times radio transmission technology ( IxRTT) offers up to 144 Kbps throughput. Pricing plans for these services usually add about $15 to the monthly bill, with additional charges for large data transfers.

Even though some mobile phone operators have spent many billions of dollars to acquire national licenses, third generation (3G) wireless data technology is not yet widely deployed. With 3G services, as an extension of GSM or CDMA, there is a promise of data rates from 144 Kbps (mobile) up to 2 Mbps (fixed).

One attraction of these data services is that they support the full range of mobile devices, including cell phones, PDAs, intelligent pagers, and laptop computers. With one-third of our work force engaged in telecommuting, at least on a part-time basis, the synergy between widely available digital wireless and IP-Centrex services will become invaluable.

Extended Ethernet
The extended Ethernet is the transmission of IP data packets over optical fiber, especially dense wavelength division multiplexed (DWDM) fiber, between the customer's premises and a managed network. This is an extremely competitive market in medium-to-large urban areas, with IP over DWDM being sold by ILECs, CLECs, cable companies, and electrical power distributors. Additionally, some organizations, such as municipal and regional governments, may have laid their own optical fiber links for specific applications. In this environment of bandwidth overcapacity, it is possible to obtain a 100-Mbps IP local access link for less than $500 per month, which is almost equivalent to the cost of a tariffed T1 link (i.e., 1.5 Mbps) from the incumbent telco. Against this low rental there will probably be an installation fee (or "service charge") of 10 month's rental, or a 3-year commitment to gain free installation.

Our three concerns with these financially attractive broadband, optical fiber solutions are:

- The QoS from the service provider may be diluted because of intense price competition between carriers.

- Some vendors are likely to withdraw from this market or fail commercially because margins may be too low to pay for ongoing network management and maintenance.

- The optical fiber network of any one carrier may not be able to serve all of the customer's locations in a given city. In spite of complicating affairs for management, we frequently have to cope with a multivendor situation
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