Qwest

Network Based VOIP 

Centrex

Centrex is a set of specialized business solutions (primarily, but not exclusively, for voice service) where the equipment providing the call control and service logic functions is owned and operated by the service provider and hence is located on the service provider's premises. Since Centrex frees the customer from the costs and responsibilities of major equipment ownership, Centrex can be thought of as an outsourcing solution. Call control and service logic refer collectively to the functions needed to process a telephone call and offer telephone features. In traditional Centrex service (i.e., analog Centrex and ISDN Centrex), call control and service logic reside in a Class 5 switch located in the Central Office. The Class 5 switch is also responsibility for transporting and switching the electrical signals that carry the callers' speech or other information (e.g., faxes).   

Packet + Centrex = IP Centrex

In IP telephony, voice conversations can be digitized and packetized for transmission across the network. IP Centrex refers to a number of IP telephony solutions where Centrex service is offered to a customer who transmits its voice calls to the network as packetized streams across a broadband access facility. IP Centrex builds on the traditional benefits of Centrex by combining them with the benefits of IP telephony. One of these IP telephony benefits is increased utilization of access capacity. In IP Centrex, a single broadband access facility is used to carry the packetized voice streams for many simultaneous calls. When calls are not active, more bandwidth is available for high speed data sessions over the LAN, like Internet access. This is a much more efficient use of capacity than traditional Centrex. In analog Centrex, one pair of copper wires is need to serve each analog telephone station, regardless of whether the phone has an active call; one the phone is not engaged in a call, the bandwidth capacity of those wires is unused. An ISDN BRI can support two simultaneous calls (i.e., 128 kbps), but similar to analog lines, an idle BRI's bandwidth capacity cannot be used to increase the corporate LAN's interconnection speed. IP Centrex is not dependant on any particular manufacturer’s IP Telephony equipment. The end user plugs in their IP phone to their Internet access and the translation and call routing is handled by the Carrier. Large customers that have multiple locations as part of a single network may even utilize 4 or 5 digit dialing across the Internet.  

General Centrex Benefits/Justifications

The following benefits apply to IP Centrex as well as to earlier Centrex technologies:

Lower capital investment cost: Since the service provider owns the infrastructure, the start-up costs for Centrex service are much lower than purchasing a CPE-based solution, like key systems, traditional PBXs or IP PBXs. Scalability: With Centrex service, the customer can buy the exact number of lines that are needed, and readily add or remove lines. In contrast, when you remove a station from a PBX, there is no cost savings, since the equipment was already purchased. Also, when adding stations to a PBX, there are costs not only for the line cards, but periodically for new common equipment, like shelves to accommodate the line cards. Simplicity: With Centrex service, the service provider is responsible for installing and configuring the service. With a PBX, the customer, or the customer's consultant, takes on this responsibility. Operations and Maintenance: The service provider is responsible for the day-to-day operations and maintenance of Centrex. This includes adding new lines and changing faulty components. With a PBX, the customer is responsible for these functions, as well as for keeping an inventory of spare parts. Upgrades: One of the principles of Centrex is that the service provider continues to upgrade the service. This includes not only the major evolutionary upgrades, like from analog to IP, but also more mundane upgrades, like installing a new switch generic which offers more features. Reliability: The Centrex service provider monitors the network 24 x 7 and has staff to immediately respond to alarms and equipment failures. Standardized CPE: Centrex station equipment uses standardized protocols and conforms to an open interface. This allows multiple equipment suppliers to manufacture Centrex CPE, and the customer can purchase any suppliers' brand of CPE. This competition drives down station equipment prices. In contrast, many PBXs use proprietary station sets, and the customer can purchase only the station sets designed to work with a particular PBX. Since the customer is locked into a limited selection of CPE, PBX station prices are often higher than comparable Centrex station equipment. Eliminate floor space and environmental requirements: With Centrex service, the infrastructure is located on service provider premises. In contrast, PBX and key system solutions are located on the customer premises. The customer must provide floor space for the equipment. The customer must ensure that the room the equipment is in meets certain environmental requirements, such as air conditioning, humidity, and fire protection. Features: Of course, Centrex offers a wide range of business-oriented features that can be configured to meet the customer's needs.   

New IP Centrex Benefits/Justifications

The IP Centrex user can be served off of an Ethernet connection or a traditional phone connector. So customers who want to take advantages of the benefits offered by a new IP phone can do so; those who want to keep their analog phone sets can also "keep on keeping on."  

The BIG deal - IP Centrex customers don't have to be literally tied to a particular "numbered pair" of

copper wires. This means a user becomes part of a distributed Centrex user group regardless of location. The implications of this "big deal" mean that the many provisioning issues for Centrex customers who are in widely different locations are much simpler.  

Convergence: IP Centrex allows the customer to combine its existing solutions for data connectivity and telephone service into a consolidated network--both within the enterprise and on the access connection to the network. Mutlilocation Centrex: Multilocation Centrex is the ability to make two or more locations part of the same Centrex group. With IP Centrex, geographic location is not a factor when defining a Centrex group. Branch offices, telecommuters, and even business travelers can be combined into a single Centrex group with the main office, even if they are all served by different wire centers. This is possible because packet transport is so inexpensive and is not mileage sensitive. Multilocation Centrex provides the following advantages to the customer: 

Easier for the corporate telecom manager to administer one large Centrex group rather than several separate Centrex groups.

Uniform services and features for all users, regardless of where their office is.

Extend advanced business features to telecommuters' homes without any Foreign Exchange costs.

Uniform dialing plan across company. Abbreviated dialing can be used to call the office next door or the office across the state.

No toll charges for calls between locations.

Better utilization of adjunct CPE solutions, such as voicemail systems or IVR equipment.

Computer Telephony Integration (CTI) and Softphones: IP Centrex promotes CTI solutions where telephone functions can be controlled by the user's PC, and where telephone information (e.g., caller id information) can be integrated with other software applications. Unlike previous CTI solutions, IP Centrex allows CTI without the need for special interface cards. The ultimate form of CTI is the softphone, where the PC actually replaces the telephone. Softphones may be particularly useful in Call Center applications. Reduction of MAC Activity: With IP Centrex, certain Move, Add, and Change (MAC) activities can be eliminated when a user (of an IP Phone) changes offices. The phone number and features follow the IP Phone throughout the LAN, without needing any change orders. Mixed Technology Groups: IP Centrex is fully compatible with previous Centrex services. Analog lines, ISDN lines, and IP Centrex lines can all be made part of the same Centrex group. This makes it simple for existing Centrex customers to introduce IP Centrex. They don't have to convert their entire group at once. Instead, they can add or convert lines to IP Centrex on a line-by-line basis.

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