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Selecting VoIP for Your Enterprise


Selecting VoIP for Your Enterprise Prepared for Global Knowledge by Technology Marketing Corporation Table of Contents Introduction Cost Savings and Other Benefits Potential Pitfalls and How to Overcome Them Voice Quality Security Emergency Services/911 Network Outages Deployment: In-house vs. Service Provider Summary Glossary 3 3 4 4 5 6 6 7 9 10 Copyright ©2005 Technology Marketing Corporation. All rights reserved. Page 2 .

But managing the system is simplified due to eliminating the need to monitor multiple networks. cost savings come in many ways. unified communications. Page 3 . the ability to collaborate among multiple branch offices. Copyright ©2005 Technology Marketing Corporation. voice mail. and lower operational expenditures as a result of simplified management schemes. By using the company’s data network. Ontario. whether they are in the same building. enterprises can eliminate all costs associated with calling between branches. corporations are able to avoid the Public Switched Telephone Network (PSTN) and the associated tolls. thus enabling extension dialing between far-flung locations. or does it make sense to outsource to a hosted services provider? How much will this cost.000 annual savings in operational expenditures over their previous system. If the data network reaches a remote location. that is enough of a reason to consider VoIP.Introduction Voice over Internet Protocol (VoIP) is a process of digitizing and sending voice telephone signals over the Internet or other data network. and how much money can I save in the long run? The first thing most people realize about VoIP technology is that it can save their business money by reducing or eliminating the toll charges for long-distance and even local calling. According to the Probe Group. be it a private WAN or the Public Internet. and click-to-dial are all enabled across the enterprise. across town. Cost Savings and Other Benefits The main benefit of VoIP technology is that it is a cost-saver.3 million dollars on a new VoIP network to serve over 2. However VoIP is more than a plan to lower a company’s phone bill.000 phones. The city is now enjoying a $700. By converting voice into packets and transporting these packets over an IP network. such as increased worker productivity. the city spent $3. All rights reserved. they can have all locations served by a single IP PBX. This paper serves as an introduction to VoIP (its benefits and potential pitfalls) and provides insight into the various options available to enterprise decision-makers who face the task of selecting a VoIP-based phone system. In the case of an enterprise with multiple branch offices. in the case of Mississauga. VoIP enables seamless call transferring to experts across a connected enterprise. Enterprises of all sizes can benefit from this technology. Of course. Furthermore.1 billion in 2008. this is especially true. Tremendous cost savings come in the form of lower telephone bills. By simply dialing a coworker’s extension. or across the globe. but they must do some research to decide if VoIP is right for them. Which vendor should I call? Would I rather deploy and manage my telecommunications in-house. Productivity enhancing applications such as conferencing. you can speak to a distant colleague as if he or she were in the very next cubicle. the market for enterprise VoIP will grow to $7. For example. so too do the telephony applications that employees at the main corporate location enjoy. For many enterprises. This presents a tremendous opportunity for numerous vendors to supply products and services to this market. There are also so-called "soft" benefits enabled by VoIP.

jitter. Furthermore.By combining separate voice and data networks into one network. or optical fiber. allowing companies to migrate to VoIP slowly. and latency. According to Tehrani’s IP Telephony Dictionary. While that has been a problem in the past. When the received pulse waveform is displayed on an oscilloscope screen. All without the need to call the phone system’s manufacturer to send a representative to make those moves. and changes. many VoIP deployments claim to have voice quality of service that is in some respects better quality than legacy communications. Potential Pitfalls and How to Overcome Them Voice Quality A serious reservation most people have is the belief that the quality of VoIP is inferior to that of traditional telecommunications. For the vast majority of enterprises considering running voice traffic over their data infrastructure. Another benefit of VoIP is that many enterprise telecommunications systems are upgraded in a piecemeal fashion. individual pulses appear to jitter or jump back and forth along the time axis. a network assessment is in order. rapid variation in arrival time of a substantially periodic pulse waveform resulting typically from fluctuations in the wave speed (or delay time) in the transmission medium such as wire. it is becoming less of an issue. here are the three culprits defined: Delay — The amount of time it takes for a signal to transfer or for the time that is required to establish a communication path or circuit. Still the problem does not simply go away. in order to maintain a healthy measure of control over the transition. Page 4 . Many enterprise VoIP solutions allow administrators to manage the system via a web-based browser interface and enable managers to enact changes to an employee’s phone and voice mail settings remotely. In fact. The costs add up quickly. In so-called "greenfield" deployments. but imagine an organization that employs thousands of people across multiple locations. VoIP also reduces the cost and complexity associated with moves. cable. (2) The short-term variation of transmission delay time for data packets Copyright ©2005 Technology Marketing Corporation. A thorough understanding of the potential return on your investment is necessary to ensure that the migration to VoIP is a cost-effective endeavor. adds. There are still impediments to voice quality that need to be addressed. All rights reserved. Any problems that pop up in early phases of deployment can be worked out before migrating the next group of users. there is no need to run two separate network cables (one each for voice and data). VoIP practically eliminates that expense. It may not take much work to physically move a single phone or to set up a new employee’s voicemail system. In fact most businesses will need to spend some capital to upgrade their networks to be capable of delivering a consistent high-quality voice experience. Let’s take a look at some of the more common problems experienced in a VoIP call: delay. department by department. VoIP enables cost savings from a network infrastructure perspective as well. adds. Jitter — (1) Jitter is a small. network administrators need manage only the single converged network. and changes.

Other concerns include the "hijacking" of a voice gateway to place unlimited unauthorized free calls across the globe. Keep in mind that delay can creep in at many points throughout the network that are beyond your control. Page 5 . and as such is the goal to strive for. The MOS rating system is judged on a five-point scale where a score of 1 implies poor quality. all of these terms deal with the impediment to transmission of VoIP packets. Latency — Latency is the amount of time delay between the initiation of a service request for data transmission or when data is initially received for retransmission to the time when the data transmission service request is granted or when the retransmission of data begins. And delayed or missing packets spell doom to quality VoIP communications.that usually results from varying time delays in transmission due to different paths or routing processes used in a packet communication network. If troublemakers were to break into a company’s voice system. or mean opinion score. As such. All rights reserved. Unacceptable! According to the International Telecommunications Union. Also.0. the variance of interpacket arrival times. As you can see. it’s important to separate voice equipment behind firewalls—frequently updated with the latest patches and monitored to keep an eye-out for intruders. acceptable delay for VoIP calls can be described as follows: • 0 to 150 milliseconds is acceptable for most any application. Toll quality telephone service is generally granted a MOS score of 4. That delay is imperceptible to the end user. So it is imperative to employ a quality of service solution that keeps the delay to an absolute minimum on the originating side of the call. and a score of 5 is excellent. Consider that if you send an e-mail that arrives with a two-second delay. Most VoIP solutions are deployed on servers that run either proprietary operating systems or on commercially available servers such as those offered by Microsoft. (3) In IP telephony. Still others believe that VoIP has a number of peculiarities that demand more specific attention. • 150 to 400 milliseconds is acceptable for international connections. vast amounts of potentially sensitive data would be at risk. Security Security is another critical issue facing enterprises interested in deploying VoIP. Now imagine that same delay in the middle of a conversation. This measurement is determined by an actual group of human listeners who rate the quality of audio on samples played to them. eavesdropping is of great concern to executives who would prefer their phone calls to be as secure as possible. Some industry professionals believe that VoIP in the context of network security needs to be addressed as simply another data application on that network. Certainly this is an area that needs to be addressed in any network deployment of voice. These servers are as susceptible to hacking or denial-of-service attacks as any other servers deployed in an enterprise IT department. Copyright ©2005 Technology Marketing Corporation. Voice quality is calculated by a measurement called MOS.

who uses a softphone. All rights reserved. companies that are switching to VoIP have the expectation that their phone system will perform at least as well (if not better) than their legacy systems. User access should be controlled through password protection. chances are the physical location would be in the same building. While many consider this to be a service provider or residential customer concern. keeping a close eye on your network through the use of an intrusion protection solution. it is necessary to factor this into your selection criteria. travels to another city. Likewise. etc. Other general suggestions for protecting your voice traffic from security threats include: making sure to encrypt the voice stream. And phones might even be limited as to what type of calls they can place (international. also leaves an enterprise open to a security breach. Another issue involves funding of emergency 911 infrastructure. chances are emergency service personnel will respond to the main office location—wasting time and valuable resources deployed to the wrong location.The use of computer-based softphones. Enterprises can work around this shortcoming by assigning a physical location to each phone. developers are tasked with the challenge of making sure that the speed of innovation does not outstrip the ability to supply emergency services to users of VoIP. If Copyright ©2005 Technology Marketing Corporation. and having that information transmitted to the PSAP.) to make sure no unauthorized users can place calls if they are able to breach the firewall and get inside the network. There is concern among public agencies that system funding will come under attack as enterprises drop legacy phone services and deploy VoIP. Emergency Services/911 One of the more pressing concerns facing VoIP is the issue of emergency services such as 911. As VoIP enjoys rapid deployment. These devices should be encrypted. Network Outages Traditional telephone systems are powered over the lines that are drawn from the local phone company’s central office. But what happens when that employee. The problem is that when power is interrupted. VoIP phones demand a power source within the enterprise. 900 number restrictions. which is not a problem. there are a number of concerns for enterprises that should be addressed. When selecting a VoIP phone system for your enterprise. making sure your firewalls are properly configured. One current limitation of VoIP is that the caller ’s physical location is not broadcast to the emergency services’ PSAP (public safety answering point). and taking precautions to secure your servers as you would for other critical business infrastructure and applications. or simply chooses to work from home? If an emergency call is placed to 911 from the caller’s new location. VoIP users can avoid paying appropriate 911 surcharges while still using the service provided by their VoIP service provider. This way emergency services workers can respond to the exact location of an injured employee. the phone systems will not work. Customers have an expectation that they can reach you whenever they need to. and even IP handsets. and it is extremely rare for these phone systems to suffer outages due to problems with supplying electricity. A business’ phone system is critical. Page 6 . Even if that employee switched offices and took his or her IP phone. This is not the case for VoIP phone systems.

and it is imperative that you ask your provider to explain how they work and why they are important. Other power issues revolve around supplying power to the individual phones that reside on people’s desks. These devices come with a varying amount of battery backup power. Service Provider While there are many choices when it comes to enterprise VoIP. with the exception of the telephones. With IP PBX. Deployment: In-house vs. If multiple branch offices are served from a central server. it is important to make sure that there are no disturbances in the power supply or else the quality may be affected at the branches. Gartner also predicts strong growth in the enterprise IP telephony space with a 34 percent CAGR of Pure IP-PBX line shipments out to 2008. without the need to modify the existing infrastructure. redundant systems. as well as other devices over existing LAN wiring. Gartner. regardless of geography or type of telephone. Some of the solutions a business needs to look into are an uninterruptible power supply (UPS). you should consider outfitting your branches with UPSs in case localized power outages occur. high-quality power that will not degrade the telecom equipment. and increase the ability to nip any problems in the bud. in the end the basic decision boils down to deploying the solution in-house versus having a service provider supply the solution in a hosted fashion (IP Centrex). Furthermore. and in fact most of the equipment. an industry analyst firm based in Stamford. Users do not own the equipment. with either system.a new phone system with all the bells and whistles promised by VoIP sits idle for lack of a well thought out power plan. A UPS will continue to supply power to the phone system for a limited time until the main power is restored. Essentially. Both approaches are viable. giving users access to the office telephone system remotely or at the company. and remote management and monitoring. softphone. They just want to know that their phones work. Individual users probably will not even know or care if their company has IP Centrex or an IP PBX. With IP Centrex. The decision depends on what’s right for your enterprise. With either choice. whether IP telephone. Furthermore. CT. resides at the remote IP Centrex site. users buy the equipment and maintain it at their site. a remote monitoring system will allow you to see if there are any power issues within your network. this solution maintains power to the telephones for as long as the battery backup remains active. All rights reserved. Power over Ethernet is able to supply power and data to IP phones. Page 7 . Lastly. Among the benefits provided by this technology is that it obviates the need to run power and data cabling to each desktop phone location. not at the user site. This will help response time. it amounts to nothing. Copyright ©2005 Technology Marketing Corporation. predicts that business lines supplied as part of local VoIP carrier services in the United States (which includes IP Centrex) will grow at an 83 percent compound annual growth rate (CAGR) out to 2008. As with buying or leasing a car. or wired phone. when used in conjunction with a UPS. you still get phone services and equipment with similar voice quality and reliability. the features reach across the network. it is like leasing. Power over Ethernet solutions abound.

For users concerned with disaster recovery and survivability. there isn’t a clear winner. and overall feature set. There is no doubt that ownership equates control. because the provider of IP Centrex services can be based anywhere and still provide services. IP Centrex systems are also very reliable during a disaster. The upside is that once the system is running smoothly. companies can have IP telephony in as many offices or home offices as they’d like. they can basically function as nodes off the home office’s IP PBX or from the IP Centrex. users can move the phones wherever there is Internet access without the traditional service charges for moves. IP Centrex can usually reroute calls very swiftly. Today. if the disaster happens at the IP Centrex Switch. whether it’s an IP PBX or IP Centrex. the user pays on a periodic basis. Geography does not matter. It all depends on where the disaster takes place. The jury is still out on what the best solution is for a company with multiple sites. There is not a steep upfront cost—but the cost is ongoing. say more than five years. buying an IP PBX may make more sense. Since IP phones or softphones can be plugged in anywhere there is Internet access. especially if it comes with the ability to migrate to future systems and/or grow to accommodate the company’s growth. For IP PBX systems. Page 8 . For companies that do not have the staff or bandwidth to implement an IP PBX. As with leasing cars. With either system. security features have become a major consideration in today’s telecom decision. What it really comes down to is preference: • If you want to own it a long time. Calls need to be automatically rerouted when the system goes down.With IP Centrex. Copyright ©2005 Technology Marketing Corporation. the IP PBX might be cheaper in the long run. The one advantage IP PBX systems have is that because users can set it up themselves. What does matter is the vendor’s reputation and track record for quality. adds. maintain. it becomes a major issue for the enterprise. Owning an IP PBX means there is a significant up-front commitment to install. IP Centrex may be the best way for them to get the benefits of IP telephony. the upfront cost can be significant or it can be financed to make it more affordable. users can be connected very quickly in the event of a disaster. or changes. IP Centrex providers charge much like a wireless provider. With either IP Centrex or IP PBX. In fact. it is typically less expensive to add new users than with IP Centrex. the system. but it also means that there is a learning curve. and because the IP phones can be plugged in anywhere. Choosing a vendor plays a key role. As well. without any geographic limitations. All rights reserved. both IP Centrex and IP PBX are very reliable systems. it should stay that way for a very long time. For maximum survivability. needs to be redundant and not physically co-located. reliability. However. and learn how to use the system. All these considerations should be factored into the total cost of ownership. billing a contracted monthly rate plus a variable rate for additional services. if a company plans to keep its system for a while. they have the control to establish the level of potential disaster recovery that is a priority for their business. if it occurs at the client site. With an IP PBX. because all the data and infrastructure is already built into the telephone system.

enhance efficiency. Our courses and enhanced. Our expert instructors draw upon their experiences to help you understand key concepts and how to apply them to your specific work situation.globalknowledge. • If you want basic services (calls in. and as with any major or call 1-800-COURSES to speak with a sales representative. Enterprises need to figure out if VoIP is right for them. Page 9 . Learn More Learn more about how you can improve productivity. And if so. as businesses who are shopping for phone systems are increasingly turning to VoIP as their first choice. which approach works best: hosted or in-house. Both approaches are viable. visit www. and many potential pitfalls that you need to be aware of before making the final move to VoIP. But there are many elements to consider when selecting an enterprise VoIP phone system. buy the IP PBX. from lower ongoing telecommunications bills to soft benefits such as increased worker productivity and the ability to conduct ad hoc collaborative sessions across multiple locations. and sharpen your competitive edge.• If you want to keep the system a shorter time. hands-on labs offer practical skills and tips that you can immediately put to use. your migration to VoIP should be a positive experience. Check out the following Global Knowledge courses: Voice over IP Deploying VoIP in the Enterprise Converging Voice and Data Networks Cisco Voice over IP Telecommunications Fundamentals I Telecommunications Fundamentals II For more information or to register. yet both have their drawbacks. Consider the trade-offs and be clear on what you really must have in your system today and into the future. one needs to do some research before deciding on how to proceed. Summary VoIP is proving to be a viable new alternative to traditional telecommunications solutions in the enterprise. IP Centrex might not cost you as much up front and you can contract for less time. But telecommunications is the lifeblood of an enterprise. Choose from our more Copyright ©2005 Technology Marketing Corporation. The decision depends on what’s right for your situation. VoIP offers many benefits. calls out) use IP Centrex. • If you want special services or customization. VoIP is the future of enterprise telecommunications. All rights reserved. If you arm yourself with the right questions and a thorough understanding of your needs.

Speech-World. A firewall continuously looks for data patterns that indicate unauthorized use or unwanted communications to the FCC — Federal Communications Commission Firewall — A firewall is a data filtering device that is installed between a computer server or data communication device and a public network (e. images. TMC Labs. All rights reserved.tmcnet. and the online publications. Page 10 . and The Global Call Center Outsourcing Summit. The fiber optic transmission is used to provide broadband services beyond the central office. TMC also produces The VoIP Developer Conference. WiFi Telephony Magazine. the Internet). and On-site sessions. delivered through Classrooms. to meet your IT and professional skills training needs. TMCnet. Speech-World Conference. Glossary CAGR — Compound annual growth rate. and BiometriTech. WiMAX Magazine. Planet PDA Magazine. VoIP Developer. SIP Magazine. TMCnet. visit its web site at www. A telephone service company that provides local telephone service that competes with the incumbent local exchange carrier (ILEC).com publishes more than 25 topical online newsletters." FTTH — Fiber to the home. or video. A distribution system that uses fiber optic cable to connect telephone networks to nodes that are located near homes or any business environment (near the curb). CTI — Computer Telephony Integration. Alternative Power. e-Learning. all the way to the last 50-100 feet from the subscriber. The year over year growth rate of an investment over a specified period of time. Normally the term codec applies only to compression of human-perceived signals such as speech. and it usually refers to lossy IP Contact Center Summit. and subsequently recovering the original data (decoding). About Technology Marketing Corporation Technology Marketing Corporation (TMC) publishes two magazines: Customer Inter@ction Solutions. A distribution system that uses fiber optic cable to connect telephone networks to nodes that are located in the homes of customers. For more information about TMC. Codec — Coder/Decoder A technique for compressing information to a fewer number of bits for more efficient transmission and storage (coding). FTTC — Fiber to the curb. Delay — The amount of time it takes for a signal to transfer or for the time that is required to establish a communication path or circuit.than 700 courses. The service pedestal is said to be "at the subscriber's curb. WiFi Revolution.g. TMC is also the first publisher to test new products in its own on-site laboratories. audio. and Internet Telephony. The fiber optic transmis- Copyright ©2005 Technology Marketing Corporation. CLEC — Competitive Local Exchange Carrier. Firewalls vary in the amount of buffering and filtering they are capable of providing.

It also describes signaling protocols for managing audio and video streams. call transfer. MGCP. video. as well as procedures for breaking data into packets and synchronizing transmissions across communications channels. The G. voice mail waiting indication and others. IPBX systems are often local area network (LAN) systems that interconnect IP telephones. The G.323. intercom features. Copyright ©2005 Technology Marketing Corporation. and data between a pair of videoconferencing workstations. IPBX systems use a IP telephone server to provide for call processing functions and to control gateways access that allows the IPBX to communicate with the public switched telephone network and other IPBX's that are part of its network. and voice mail along with integrating computer telephony applications.323 specifies techniques for compressing and transmitting real-time voice. but offer clear advantages over TDM-based PBX. IP Centrex allows customer to have and use features that are typically associated with a private branch exchange (PBX) without the purchase of PBX switching systems. It has a relatively high voice quality level for the low 8 kbps data transmission rate.729: G.729 A. and potentially a richer feature set. ILEC — Incumbent local exchange carrier.729 — A low bit rate speech coder that was developed in 1995. The G. IP PBX supports both voice and data. A telephone carrier (service provider) that was operating a local telephone system prior to the divestiture of the AT&T bell system. whereas their successor is designed for converged applications.729 and G. and SIP. G. These features include 3 or 4 digit dialing. G. All rights reserved. distinctive line ringing for inside and outside lines. G. There are two versions of G. It has low delay due to a small frame size of 10 msec and look ahead of 5 msec. all the way through the drop wire to the optical node that is located in the customers home. IP PBX represents the evolution of enterprise telephony from circuit to packet. H. IP PBX — A private local telephone system that uses Internet protocol (IP) to provide telephone service within a building or group of buildings in a small geographic area.323 — H. IP Centrex — IP Centrex is the providing of Centrex services to customers via Internet protocol (IP) connections.323 is an umbrella recommendation from the International Telecommunications Union (ITU) that sets standards for multimedia communications over Local Area Networks (LANs) that may not provide a guaranteed Quality of Service (QoS). MEGACO. mainly in terms of reduce Opex (operating expenses). H. Some of the IPBX standards include H.723 — An International Telecommunication Union (ITU) standard for audio codecs that provides for compressed digital audio over standard analog telephone lines.711 — A standard analog to digital coding system (coded) that converts analog audio signals into pulse code modulated (PCM) 64 kbps digital signals.711 standard was approved in 1965.sion is used to provide broadband services beyond the central office. IPBX systems can provide advanced call processing features such as speed dialing. Traditional PBX systems are voice-based.711 standard allows for different weighting processes of digital bits using mu-law and A-law coding.711 is an International Telecommunications Union (ITU) standard for audio codecs. Page 11 . Current IP PBX offerings vary in their range of features and network configurations.

A United States telephone company that is one of Copyright ©2005 Technology Marketing Corporation.0. Public telephone networks within countries and regions are standard integrated systems of transmission and switching facilities. individual pulses appear to jitter or jump back and forth along the time axis. These stand alone devices plug into (connect to) data networks (such as the Ethernet) and operate like traditional telephone sets. Page 12 . and associated operations support systems that allow communication devices to communicate with each other when they operate. rapid variation in arrival time of a substantially periodic pulse waveform resulting typically from fluctuations in the wave speed (or delay time) in the transmission medium such as wire. RBOC — Regional Bell Operating Company. minimum committed bit rate (CBR) and other measurements that are used to ensure quality communications service. QoS measures may include service availability. Good quality telephone service (called "toll quality") has a MOS level of 4. The rating level varies from 1 (bad) to 5 (excellent). PSAP — Public safety answering point. maximum bit error rate (BER). An agency that receives and processes emergency calls. (3-IP Telephony) The variance of interpacket arrival times. The MOS is number that is determined by a panel of listeners who subjectively rate the quality of audio on various samples.IP Phone — An Internet protocol phone (IP phone) is a device (a telephone set) that converts audio signals and telephony control signals into Internet protocol packets. All rights reserved. Some IP Telephones create a dialtone that allows the user to know that IP telephone service is available. ISP — Internet service provider Jitter — (1-general) Jitter is a small. When the received pulse waveform is displayed on an oscilloscope screen. The PSAP usually receives the calling number identification information that can be used to determine the location of the caller. A private telephone network used within an enterprise. (2-packet) The short-term variation of transmission delay time for data packets that usually results from varying time delays in transmission due to different paths or routing processes used in a packet communication network. PSTN — Public switched telephone networks are communication systems that are available for public to allow users to interconnect communication devices. MOS — Mean opinion score (MOS) is a measurement of the level of audio quality. cable or optical fiber. PBX — Private Branch eXchange. QoS — Quality of service (QoS) is one or more measurements of desired performance and priorities of a communications system. signaling processors. LAN — Local-area network Latency — Latency is the amount of time delay between the initiation of a service request for data transmission or when data is initially received for retransmission to the to the time when the data transmission service request is granted or when the retransmission of data begins.

WAN — Wide-area network Copyright ©2005 Technology Marketing Corporation. ROI evaluates the impact of an investment on the telephone company's profitability or operational efficiency: dollars spent compared to benefits gained. ROI — Return on Investment is a financial measurement that compares the profit with the original investment. bridges. SIP is a simplified version of the ITU H. Page 13 . Nynex. If the telephone signal is in analog form (voice or fax).the seven telephone companies that were created as a result from the division of AT&T in 1983. A UPS system is particularly important for network servers. and gateways. Bell Atlantic. the signal is first converted to a digital form. All rights reserved. SMB — Small and medium businesses SOHO — Small office.323 packet multimedia system. SIP — SIP is an application layer protocol that uses text format messages to setup. The RBOCs were Ameritech. and terminate multimedia communication sessions. BellSouth. VoIP — A process of sending voice telephone signals over the Internet or other data network. Packet routing information is then added to the digital voice signal so it can be routed through the Internet or data network. Pacific Telesis. and US West. home office UPS — A battery backup system designed to provide continuous power in the event of a commercial power failure or fluctuation. Southwestern Bell Corporation. manage. RBOCs are also known as the Baby Bells. SIP is defined in RFC 2543.