Concerns with IP-Centrex

Concerns with IP-Centrex
We must be aware of the potential issues associated with IP-Centrex, which may not be present with legacy Centrex services. As outlined, a number of requirements must be fulfilled for a successful implementation of IP-Centrex. These major issues are summarized as follows.

Operational Costs
The single most significant issue surrounding the use of Centrex services, legacy or IP-based, is the recurring operational cost. This is the monthly charge made by the provider for supplying IP-Centrex services and related applications.

In financial evaluations, this cost is most often compared to the sum of capital and operational costs of an in-house telephony system over a specified period of time.

Stability
PBX and CO switching technologies have been developed over a number of decades. Thousands of person-years have been invested in software and hardware engineering to create an exceptionally reliable and ubiquitous service. Enterprise-scale IP telephony technology is relatively new and has not achieved the installed base and extensive long-term field-testing of existing circuit-switched technologies. A risk associated with IP Centrex services is that they are based on emerging technologies with complex software. Providers will have to be extra vigilant to ensure the reliability of IP-Centrex infrastructure components.

Security
The Internet revolution has seen a new breed of individuals evolve: hackers. While the compromising of traditional telephony services (long distance and DISA) has long since been exercised by inventive and unlawful individuals, the advent of IP telephony opens up an entirely new twist to this old story. It is foreseeable that hackers, who currently practice their trade on both the Internet and corporate data networks, will now have much more access to, and control of, telephony services. This could evolve into a serious issue; most IP telephony systems are based on widely used operating systems and protocols, which are well-known to the hacker community. A considerable number of techniques currently exist to attack or use the resources of existing data network-based services, the realm of which telephony has now entered. A hacker at a distant location could, given the appropriate access and knowledge, attack, control, or cripple elements of IP-Centrex.

Whether IP-Centrex or private IP telephony is used by an organization, security of the internal network must be given increasing priority, in order to guard against service disruptions and the loss or compromise of corporate and personal assets and privacy.

Network Considerations
Since IP telephony, and hence IP-Centrex, are required to run over the LAN of a customer's organization, that network must have the inherent capability of carrying such traffic. Latency, jitter, and bandwidth characteristics of the LAN must be within tolerable limits for packet voice traffic. These parameters, otherwise known as quality of service (QoS), are created and sustained by both the architecture of the network and the capability and configuration of the electronic equipment (switches and routers) used to build the LAN on which packet voice traffic will flow.

A number of other network considerations must be made when deploying IP telephony technology, such as dynamic host configuration protocol (DHCP), a network service that provides each IP phone with a unique IP address at startup. This could be supported by the provider, but because of the potential in-house requirements of directory integration and other needs, may have to be supported in-house.

A consequence of convergence is that the failure of part or all of an organization's LAN also means the failure of telephony services. While users of traditional voice networks have enjoyed exceptional reliability, this has not been the case historically with LAN infrastructures and for PC users. Therefore, appropriate amounts of redundancy must be built into the LAN infrastructure to provide for high availability (upward of 99.9%). This is usually accomplished through numerous hardware and software techniques, including redundant power supplies, duplicated backbone links, and routing redundancy. Organizations should plan to invest around 15% over the base capital cost of implementing a LAN to increase its reliability.

911 Requirements
The service provider will have to create the capability of connecting 911 services into the IP-Centrex environment. Basic 911 requirements dictate that a caller must be routed to a public safety answering point (PSAP), with information on the caller location provided by ANI and other database information. This can usually be accomplished with IP-Centrex. Enhanced 911 has the extended requirement of being able to locate a caller to within a particular area of a building or campus, or within a limited number of logically grouped telephones. Enhanced 9 1 1 therefore requires substantially more intelligence from the telephony and LAN infrastructure. Such capabilities can be accomplished by having intelligence built into the LAN, whereby an IP phone set and the particular port on an active LAN switch can be queried by management software, which in turn provides a database search for a location of that phone set. This information will have to be passed to the provider and ultimately (and in a timely manner) to the PSAP.

Due to the geographic independence of IP telephony, both IP-Centrex providers and in-house IP telephony systems must provide for appropriate routing of 911 calls to the local PSAP, as opposed to traversing an internal LAN / WAN and connecting to the PSTN at some unrelated location.

Phone Power
Like residential telephones, most traditional Centrex sets are powered from the CO. With IP Centrex however, multiple phone sets (connected to an in-building LAN) cannot derive power from the CO and must be locally powered. This local power is derived in one of two ways: a phone-based power adapter or in-line power. In either case, the power located in the building is used, which may be subject to a number of anomalies and often has no backup (UPS or emergency power). CO power however is quite reliable because it is typically supported by both battery and a diesel generator for longer outages.

A phone-based power adapter is a small ac/dc power transformer cube connected to a standard ac power outlet near the IP telephone; it provides the necessary power to the set.

In-line power is delivered on the same cable as signaling. Power is "injected" onto the cable either from a special patch panel or by the network Ethernet switch itself (on a per-port basis). In-line power can also be used to power wireless LAN access points, which would be in support of wireless in-building IP-Centrex.

Broadband Connectivity and Call Processing
Reliance on a single broadband connection from the CO for telephony services creates a potential single point of failure. While this is also true of legacy Centrex services and their multipair copper cables from the CO, IP-Centrex can be additionally protected if the telco provides some element of redundant IP call-processing equipment at the customer location. This could provide very basic call capability until normal services are restored. In addition, redundant broadband connectivity should be established, at an additional cost, ideally through a physically separate connection with another carrier. Such a connection could also be created using a lower-performance (and hence, lower-cost) link until the main link is restored.

Messaging and Directory Integration
It is anticipated that the use of an internal IP-PBX will allow an organization to configure unified messaging and directory services in a more controlled and secure manner than with the use of an IP-Centrex service, which might require significantly more involvement between the customer's and the service provider's management. Since internal e-mail systems and network-based directories are cornerstones of data networking, telephony integration to these elements in larger organizations will be vitally important.

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.