FURTHER READING: As a preview for further reading, the following reference has been provided from the pages of the book below:

Size: px
Start display at page:

Download "FURTHER READING: As a preview for further reading, the following reference has been provided from the pages of the book below:"

Transcription

1 FURTHER READING: As a preview for further reading, the following reference has been provided from the pages of the book below: Title: Signaling System #7 Second Edition Author: Travis Russell Publisher: McGraw-Hill ISBN:

2 Chapter 1 Signaling System #7 Early telephone networks were the result of years of evolution, with little thought about future technology. Based around analog equipment, the telephone network of the early telephone company was not well suited for services such as data and video. Many individual technology service providers began popping up during the 1960s, providing packet-switching networks and data communications services the telephone companies were just not equipped to provide. The international telephone network was facing the same problems. In many countries, just getting telephone service was a feat in itself. As international bodies began investigating alternative technologies for providing telephone service to the masses (such as cellular), the need for an all-digital network became apparent. Thus arose the beginnings of an all-digital network with intelligence. The International Telecommunications Union (ITU) commissioned the then CCITT to study the possibility of an all-digital intelligent network. The result was a series of standards known now as Signaling System #7 (SS7). These standards have paved the way for the Intelligent Network (IN) and, with it, a variety of services, many yet to be unveiled. This book outlines the technologies related to the SS7 protocols and details how the protocols work within the Intelligent Network (IN). Introduction to SS7 The ITU-TS (once known as the CCITT) developed a digital signaling standard in the mid-60s called Signaling System #6 that would revolutionize the telephone industry. Based upon a proprietary, high-speed data communications network, SS6 later evolved into SS7, which has now become the signaling standard for the entire world. 1

3 2 Chapter One The secret to its success lies in the message structure of the protocol and the network topology. The protocol uses messages, much like X.25 and other message-based protocols, to request services from other entities. These messages travel from one network entity to another, independent of the actual voice and data they pertain to, in an envelope called a packet. Common Channel Signaling (CCS) was first introduced in the United States in the 1960s as Common Channel Interoffice Signaling System #6 (SS6). Developed by the International Telecommunications Union Telecommunications Standards Society (ITU-TS), SS6 used a separate facility for sending signaling information to distant telephone offices. The first deployment of SS6 in the United States used 2.4-kbps data links. These were later upgraded to 4.8 kbps. Messages were sent in the form of data packets and were used to request connections on voice trunks between two central offices. This became the first use of packet switching in the Public Switched Telephone Network (PSTN). The packets were assembled by placing 12 signal units of 28 bits each into a data block. This is similar to the method used in SS7 today. Signaling System #7 (SS7) was derived from the earlier SS6, which explains the similarities. SS7 provides much more capability than SS6. Where SS6 used fixed-length signal units, SS7 uses variable-length signal units (with a maximum sized length), providing more versatility and flexibility. SS7 also uses high-speed data links (56 kbps). This makes the signaling network much faster than SS6. In international networks, the data links operate at 64 kbps. Study is under way to increase this in the United States to Mbps, and internationally to Mbps. As of 1983, SS6 was still being deployed throughout the United States telephone network, even though SS7 was being introduced. As SS7 began deployment in the mid-1980s, SS6 was phased out of the network. SS7 was used in the interoffice network and was not immediately deployed in the local offices until many years later. In fact, the first usage of SS7 was not for call setup and teardown, but for accessing remote databases. In the 1980s, the telephone companies offered a new service called Wide Area Telephone Service (WATS), which used a common 800 area code regardless of the destination of the call. This posed a problem for telephone-switching equipment, which uses the area code to determine how to route a call through the Public Switched Telephone Network (PSTN). To overcome this problem, a second number was assigned to every 800 number. This second number is used by the switching equipment to actually route the call through the voice network. But the number had to be placed in a centralized database where all central offices could access it. This database became a popular commodity for all telephone companies and still exists today.

4 Signaling System #7 3 When an 800 number is dialed, the telephone company switching equipment uses a data communications link to access this remote database and look up the actual routing number. The access is in the form of a message packet, which queries the network for the number. The database then responds with a response message packet, providing the routing telephone number as well as billing information for the 800 number. The switching equipment can then route the call using conventional signaling methods. SS7 provides that data communications link between switching equipment and telephone company databases. Shortly after the 800 number implementation, the SS7 network was expanded to provide other services, including call setup and teardown. Still, the database access capability has proven to be the biggest advantage behind SS7 and is widely used today to provide routing and billing information for all telephone services including 800 numbers, 900 numbers, 911 services, custom calling features, caller identification, and many new services yet to be offered. 800 numbers at one time belonged to one service provider. If subscribers wanted to change service providers, they had to surrender their 800 number. This was due to the location of the routing information. All routing information for 800 numbers is located in a central database and accessed via the SS7 network. SS7 is now used to allow 800 numbers to become transportable and to provide subscribers the option of keeping their 800 numbers even when they change service providers. Without SS7, number portability would be impossible. Local Number Portability (LNP) is a service mandated by the FCC in 1996 which requires telephone companies to support the porting of a telephone number. If customers wish to change their service from Plain Old Telephone Service (POTS) to ISDN, they would normally be forced to change telephone numbers. This is because of the way telephone numbers are assigned in switching equipment, with switches assigned ranges of numbers. With LNP, the telephone number does not change. This requires the use of a database to determine which switch in the network is assigned the number, very similar to the way 800 numbers are routed. Future implementations of LNP will support subscribers moving from one location to another without changing their telephone number (even if they move to a new area code). This obsoletes the former numbering plan and the way calls are routed through the telephone network. In addition to database access, the SS7 protocol provides the means for switching equipment to communicate with other switching equipment at remote sites. For example, if a caller dials a number which is busy, the caller may elect to invoke a feature such as automatic callback. When the called party becomes available, the network will ring the caller s phone. When the caller answers, the called party phone is then rung. This feature relies on the capabilities of SS7 to send messages from one switch to another switch, allowing the two systems to invoke features within each switch without setting up a circuit between the two systems.

5 4 Chapter One Cellular networks use many features requiring switching equipment to communicate with each other over a data communications network. Seamless roaming is one such feature of the cellular network that relies on the SS7 protocol. Cellular providers use the SS7 network to share subscriber information from their Home Location Registers (HLRs), so cellular subscribers no longer have to register with other service providers when they travel to other areas. Cellular providers can access each other s databases and share the subscriber information so that subscribers can roam seamlessly from one network to another. Before deploying SS7, cellular providers were dependent on X.25 networks to carry IS-41 signaling information through their network. This did not allow them to interconnect through the Public Switched Telephone Network (PSTN) because the X.25 network was not compatible with the PSTN signaling network (SS7). The cellular providers are aggressively changing this situation today, deploying their own SS7 networks. Today, SS7 has been deployed throughout the Bell Operating Companies network, and is being deployed by almost all independent telephone companies and interexchange carriers as well. This makes SS7 the world s largest data communications network, linking telephone companies, cellular service providers, and long distance carriers together into one large information-sharing network. SS7 supports many new features and applications. Because of its ability to transfer all types of digital information, this new network is being used to deliver many sophisticated services to the customer premises such as custom calling features, ATM, ISDN, and cellular. Many new applications are still under development. The SS7 network interconnects thousands of telephone company providers all over the world into one common signaling network. New technology will continue to place demands on the signaling network. SS7 continues to evolve and become more sophisticated as new features are added. While the network is sophisticated enough to work on its own with very little interaction from maintenance personnel, when problems do arise, knowledge of the protocols and the processes that take place between network entities is critical. Yet to fully understand what SS7 is about, one must understand the conventional signaling methods used prior to SS7 in telephone networks. The following discussion explains the signaling methods used prior to SS7. Introduction to Telephony Signaling Ever since the beginning of the telephone, signaling has been an integral part of telephone communications. The first telephone devices depended on the receiving party standing next to the receiver. Early telephones did not have ringers like today s telephones, and used crude

6 Signaling System #7 5 speakers to project the caller s voice into the room. If the party being called was not within close proximity of the speaker, he or she would have no indication of an incoming call. Later, after the formation of the Bell Telephone Company, Alexander Graham Bell s faithful assistant Watson invented the telephone ringer. This new signaling method served one purpose: to alert the called party of an incoming call. When the called party lifted the receiver, another form of signaling used DC battery and ground to indicate the called party had answered the telephone and completed the circuit. Although not having an immediate impact, this method became important when the first telephone exchange was created. By lifting the receiver and allowing DC current to flow through the phone and back through the return of the circuit, a lamp would be lit on the exchange operator s switchboard. This signaled the operator when someone needed telephone service, and was often accompanied by a buzzer. Signaling has evolved over the decades to include significantly more information than these early methods could. Consider the typical long distance telephone call today. When a caller dials the area code and prefix of the telephone number, the local exchange must determine how to route the call. In addition, billing information must be passed to a central database. If the caller is using a contemporary digital facility (such as T-1 or ISDN), information regarding the digitization of the line must also be provided. Early signaling methods were limited because they used the same circuit for both signaling and voice. They were also analog and had a limited number of states, or values, which could be represented. The circuit would be busy from the time the caller started dialing until the caller went on-hook. To compound the problem, the telephone companies were quickly running out of facilities and were in desperate need of additional facilities. Many telephone companies in metropolitan areas such as Los Angeles were facing substantial investments to add new facilities to support the millions of customers that were creating an enormous amount of traffic. The telephone companies had to find a way to consolidate their facilities, making more economical use of what they had. In addition, they needed a service that would vastly improve their network s capability and support the many new services being demanded by subscribers. Europe had already begun the process of digitizing the network in the early 60s. One of the first steps was to remove signaling from the voice network and place the signaling on a network all its own. This way, the call setup and teardown procedures required with every call could be faster than the previous methods, and voice and data circuits could be reserved for use when a connection was possible, rather than maintaining the connection even when the destination was busy. Common Channel Signaling (CCS) paved the way for services the early

7 6 Chapter One pioneers of signaling never dreamed of. CCS is the technology that makes ISDN and SS7 possible. The concept behind Common Channel Signaling (CCS) SS7 is simple. Rather than use voice trunks for signaling, they are used only when a connection is established. For instance, when a call is placed to a distant party using conventional signaling, the signaling for that call begins from the time the caller lifts the receiver and goes off-hook until the caller goes back on-hook. After the end office has received the dialed digits, an outgoing trunk to the destination end office is seized, based on a routing table entry and the digits dialed. The voice circuit remains busy even if the distant party never answers the call until the calling party hangs up. Meanwhile, other subscribers are tying up other voice circuits by placing calls of their own. This is not good utilization of voice circuits and it placed immediate limitations on the networks. But if the signaling could be placed over a different network and the voice circuit used only when the called party answered, the voice circuit would remain available for a longer period of time. This meant the availability of voice circuits would be higher and the need for additional circuits would decrease. When a caller is to receive an intercept recording ( all circuits are busy ), the same trunk used for the voice is also used for the recording. The recording is sent by the distant office. Busy tones and other service tones are sent over the trunk by the distant office to the caller. With SS7, the caller s local office can provide these tones and recordings at the command of the distant office. These commands are received via the signaling network. The voice trunk is left unconnected (although in some implementations, one side of the trunk is connected for transmitting tones and recordings). The procedure for tearing down a circuit is much faster in Common Channel Signaling (CCS) than in conventional signaling, and is not as error prone. Even if voice circuits do get connected, with the speed of the signaling network, circuits can be disconnected and quickly connected again for a new call. While a call is in progress, information regarding the call can be sent through the SS7 network (for instance, information from a database requested during an interactive multimedia call). CCS uses existing telephone company resources, so it does not require additional facilities to be installed. When signaling information is placed on existing digital transmission facilities (such as DS0 or DS1), it uses a fraction of the circuits required for in-band signaling (discussed later in this chapter). One digital data link can carry the signaling information for thousands of trunks and maintain thousands of telephone calls. CCS is in wide use today, even though many in the telecommunications business do not understand it. SS7 is the protocol and architecture used in this new network and is the topic of this book. There are many methods used for signaling, with only a few used in the telephone network. None of the methods described in this section can sup-

8 Signaling System #7 7 port network management functions or control information between switches and operations systems. The exception is SS7. Because SS7 consists of a data network using data messages, SS7 can meet the demands both now and in the future of the evolving telephone network. Signaling takes place in two parts of the telephone network between the subscriber and the local end office, and from switching office to switching office within the telephone company network. The signaling requirements are similar, though interoffice signaling can be more demanding. There are two basic functions of signaling: addressing and supervision. With the earlier methods of signaling, supervision was simple. If current existed from one end to the other, the circuit was good. For addressing, dialed digits would be passed through the network in the same fashion as they were originated, either in pulses or tones. Only the destination address could be provided. But as the telephone network grew more sophisticated, the signaling methods grew as well. Signaling between the subscriber and the central office now includes the calling party number, which is forwarded to the called party and displayed before the phone is even answered. Interoffice signaling now includes information obtained from regional databases, pertaining to the type of service a subscriber may have or billing information. Calling card validation is another important function of these databases, and provides security against telephone fraud. Personal identification numbers are kept in a subscriber database and verified every time a call is placed using a calling card. Previous to SS7, signaling was accomplished over the same facility as the voice call. This was accomplished in many cases using DC current. There are many disadvantages to DC signaling, which is what led to the development of SS7. In addition to DC signaling, many companies used Single Frequency (SF) signaling. This was also accomplished over the same facility as the voice. This method of signaling used tones above the voice frequencies, but still within the 4-kHz bandwidth of the facility to set up and tear down circuits. Other methods have been used in addition to DC and SF signaling, depending on the type of facility. But with all of the various signaling methods, none can offer the features and versatility of SS7. Conventional signaling Conventional signaling relies on many different types of mechanisms, depending mostly on the location within the network. Dual-Tone Multi- Frequency (DTMF) is used between the subscriber and the end office. Single frequency (SF) is used between telephone company offices. Following is an example of how conventional signaling is used to process a call.

9 8 Chapter One DC signaling relies on DC current to signal the distant end. The simplest example of DC signaling is used in Plain Old Telephone Service (POTS) between the subscriber and the local end office. When a subscriber goes off-hook, DC current from the central office is allowed to flow through the telephone (the switch-hook provides the contact closure between the two-wire interface) and back to the central office. The central office switch uses a DC current detector to determine when a connection is being requested. The central office acknowledges receipt of the loop current by sending a dialtone. A dialtone signals the subscriber to begin dialing the telephone number. This can be done using a rotary dial or a Dual-Tone Multi-Frequency (DTMF) dial. Rotary dials use a relay to interrupt the current creating pulses (10 pulses per second). The central office switch counts each series of pulse bursts to determine the number dialed. When DTMF is used, the dial creates a frequency tone generated by mixing two frequencies together (hence the name dual-tone). The central office switch hears these tones and translates them into dialed digits. After the telephone number has been dialed, the central office switch must determine how to connect to the destination. This may involve more than two central offices. A facility (or circuit) must be connected between every telephone company office involved in the call. This circuit must remain connected until either party hangs up. The originating office determines which circuits to use by searching its routing tables to see which office it must route the call through to reach the final destination. That office, in turn, will search its routing tables to determine the next office to be added to the call. Once the circuits are all connected, the distant party can be alerted by sending a generator (80 V AC at 20 Hz) out to the telephone. This activates a ringer inside the telephone. At the same time, the distant telephone company switch sends a ringback tone to the originator to alert the caller that the called party s phone is being rung. When the distant party answers, the ringback tone is interrupted and the circuits now carry the voice of both callers. If the called party is busy, the same facilities are used so that the far end office can send a busy tone back to the originator. This means those facilities cannot be used for any other calls and are being tied up to send the busy tone. The limitations of DC signaling are somewhat obvious. For example, the telephone number of the originator cannot be sent to the called party (at least not without long delays in setup). Signaling is limited to seizing circuits, call supervision, and disconnect. Because DC signaling uses the voice trunk, the trunks are kept busy even when the two parties are never connected.

Traditional Telephony

Traditional Telephony Traditional Telephony Basic Components of a Telephony Network This topic introduces the components of traditional telephony networks. Basic Components of a Telephony Network 3 A number of components must

More information

Three Network Technologies

Three Network Technologies Three Network Technologies Network The largest worldwide computer network, specialized for voice ing technique: Circuit-switching Internet The global public information infrastructure for data ing technique:

More information

Introduction to SS7 Signaling This tutorial provides an overview of Signaling System No. 7 (SS7) network architecture and protocols

Introduction to SS7 Signaling This tutorial provides an overview of Signaling System No. 7 (SS7) network architecture and protocols Introduction to SS7 Signaling This tutorial provides an overview of Signaling System No. 7 (SS7) network architecture and protocols SS7 is a set of telephony signaling protocols that are used to set up

More information

1. Public Switched Telephone Networks vs. Internet Protocol Networks

1. Public Switched Telephone Networks vs. Internet Protocol Networks Internet Protocol (IP)/Intelligent Network (IN) Integration Tutorial Definition Internet telephony switches enable voice calls between the public switched telephone network (PSTN) and Internet protocol

More information

PATTON TECH NOTES What are FXS and FXO?

PATTON TECH NOTES What are FXS and FXO? Introduction The question What is the difference between FXS and FXO? is frequently asked by those deploying Patton Voice-over-Internet Protocol (VoIP) SmartNode solutions. Foreign exchange Subscriber

More information

ATA: An Analogue Telephone Adapter is used to connect a standard telephone to a high-speed modem to facilitate VoIP and/or calls over the Internet.

ATA: An Analogue Telephone Adapter is used to connect a standard telephone to a high-speed modem to facilitate VoIP and/or calls over the Internet. KEY VOIP TERMS 1 ACD: Automatic Call Distribution is a system used to determine how incoming calls are routed. When the ACD system receives an incoming call it follows user-defined specifications as to

More information

Vanguard Managed Solutions. Understanding Voice Technology - Vanguard Technical Reference

Vanguard Managed Solutions. Understanding Voice Technology - Vanguard Technical Reference Vanguard Managed Solutions Understanding Voice Technology - Vanguard Technical Reference Notice 2003 Vanguard Managed Solutions, LLC 575 West Street Mansfield, Massachusetts 02048 (508) 261-4000 All rights

More information

CHAPTER 18 THE PUBLIC TELEPHONE NETWORK # DEFINITIONS TERMS

CHAPTER 18 THE PUBLIC TELEPHONE NETWORK # DEFINITIONS TERMS CHAPTER 18 THE PUBLIC TELEPHONE NETWORK # DEFINITIONS TERMS 1) It uses the largest computer network in the world to interconnect millions of subscribers in such a way that the myriad of companies function

More information

Glossary of Telco Terms

Glossary of Telco Terms Glossary of Telco Terms Access Generally refers to the connection between your business and the public phone network, or between your business and another dedicated location. A large portion of your business

More information

Fundamentals of Telecommunications

Fundamentals of Telecommunications Fundamentals of Telecommunications Professor of CIS Columbus, OH 43210 Jain@ACM.Org http://www.cis.ohio-state.edu/~jain/ 1 Overview Time Division Multiplexing T1, T3, DS1, E1 T1 Framing Echo Cancellation

More information

Data Communications & Computer Networks. Circuit and Packet Switching

Data Communications & Computer Networks. Circuit and Packet Switching Data Communications & Computer Networks Chapter 9 Circuit and Packet Switching Fall 2008 Agenda Preface Circuit Switching Softswitching Packet Switching Home Exercises ACOE312 Circuit and packet switching

More information

T1 Networking Made Easy

T1 Networking Made Easy T1 Networking Made Easy 1 THE T1 CARRIER 3 WHAT DOES A T1 LOOK LIKE? 3 T1 BANDWIDTH 3 T1 PHYSICAL CHARACTERISTICS 4 T1 FRAMING 5 LINE CODE 6 T1 NETWORKING 6 TELCOS 6 PSTN ACCESS WITH A T1 8 SUMMARY OF

More information

ADSL or Asymmetric Digital Subscriber Line. Backbone. Bandwidth. Bit. Bits Per Second or bps

ADSL or Asymmetric Digital Subscriber Line. Backbone. Bandwidth. Bit. Bits Per Second or bps ADSL or Asymmetric Digital Subscriber Line Backbone Bandwidth Bit Commonly called DSL. Technology and equipment that allow high-speed communication across standard copper telephone wires. This can include

More information

Introduction to Communication Networks Spring 2007. Unit 5 Switching Principles

Introduction to Communication Networks Spring 2007. Unit 5 Switching Principles Introduction to Communication Networks Spring 2007 Unit 5 Switching Principles Acknowledgements slides comming from: Data and Computer Communication by Wiliam Stallings (our supplementary textbook) numerous

More information

Telephony Fundamentals

Telephony Fundamentals + Telephony Fundamentals Basic Telephony general terms Central Office (CO) - the telephone facility where telephone users lines are joined together to switching equipment that connects telephone users

More information

Telecommunications systems (Part 1)

Telecommunications systems (Part 1) School of Business Eastern Illinois University Telecommunications systems (Part 1) (Week 11, Thursday 11/02/2006) Abdou Illia, Fall 2006 Learning Objectives 2 Describe and compare types of connection to

More information

White paper. SIP An introduction

White paper. SIP An introduction White paper An introduction Table of contents 1 Introducing 3 2 How does it work? 3 3 Inside a normal call 4 4 DTMF sending commands in sip calls 6 5 Complex environments and higher security 6 6 Summary

More information

Overview of the Telecommunications Network

Overview of the Telecommunications Network 1 Overview of the Telecommunications Network 15 Telecommunication Networks 2 Basic purpose of a telecommunications network: transmit user information in any form to another user of the network. Many forms

More information

Internet Telephony Terminology

Internet Telephony Terminology Internet Telephony Terminology Understanding the business phone system world can be a daunting task to a lay person who just wants a system that serves his or her business needs. The purpose of this paper

More information

APPENDIX A GENERAL DEFINITIONS & SERVICE FUNCTIONS

APPENDIX A GENERAL DEFINITIONS & SERVICE FUNCTIONS APPENDIX A GENERAL DEFINITIONS & SERVICE FUNCTIONS This Appendix provides the basic definitions and service functions of local communications services under the scope of this contract. The Government requires

More information

Course 1. General view on the fixed telephone network. Digital networks. General aspects. Definitions.

Course 1. General view on the fixed telephone network. Digital networks. General aspects. Definitions. Course 1. General view on the fixed telephone network. Digital networks. General aspects. Definitions. 1. General view on the fixed telephone network Communication network dedicated to voice transmission;

More information

FACILITY TELECOMMUNICATIONS MANAGEMENT FOR THE GOVERNMENT EMERGENCY TELECOMMUNICATIONS SERVICE Introduction

FACILITY TELECOMMUNICATIONS MANAGEMENT FOR THE GOVERNMENT EMERGENCY TELECOMMUNICATIONS SERVICE Introduction FACILITY TELECOMMUNICATIONS MANAGEMENT FOR THE GOVERNMENT EMERGENCY TELECOMMUNICATIONS SERVICE Introduction This document provides telecommunications management information for organizations that use the

More information

Contents. Specialty Answering Service. All rights reserved.

Contents. Specialty Answering Service. All rights reserved. Contents 1 Introduction... 2 2 PBX... 3 3 IP PBX... 4 3.1 How It Works... 4 3.2 Functions of IP PBX... 5 3.3 Benefits of IP PBX... 5 4 Evolution of IP PBX... 6 4.1 Fuelling Factors... 6 4.1.1 Demands from

More information

Network Overview. Background Traditional PSTN Equipment CHAPTER

Network Overview. Background Traditional PSTN Equipment CHAPTER CHAPTER 1 Background Traditional PSTN Equipment Traditional telephone services are engineered and offered over the public switched telephone network (PSTN) via plain old telephone service (POTS) equipment

More information

Packetized Telephony Networks

Packetized Telephony Networks Packetized Telephony Networks Benefits of Packet Telephony Networks Traditionally, the potential savings on long-distance costs was the driving force behind the migration to converged voice and data networks.

More information

Telecommunications Switching Systems (TC-485) PRACTICAL WORKBOOK FOR ACADEMIC SESSION 2011 TELECOMMUNICATIONS SWITCHING SYSTEMS (TC-485) FOR BE (TC)

Telecommunications Switching Systems (TC-485) PRACTICAL WORKBOOK FOR ACADEMIC SESSION 2011 TELECOMMUNICATIONS SWITCHING SYSTEMS (TC-485) FOR BE (TC) PRACTICAL WORKBOOK FOR ACADEMIC SESSION 2011 TELECOMMUNICATIONS SWITCHING SYSTEMS (TC-485) FOR BE (TC) Department of Electronic Engineering NED University of Engineering and Technology, Karachi LABORATORY

More information

Contents Introduction Why Fax over IP? How Real-time Fax over IP works Implementation with MessagePlus/Open Summary. About this document

Contents Introduction Why Fax over IP? How Real-time Fax over IP works Implementation with MessagePlus/Open Summary. About this document Fax over IP Contents Introduction Why Fax over IP? How Real-time Fax over IP works Implementation with MessagePlus/Open Summary About this document This document describes how Fax over IP works in general

More information

Methods for Lawful Interception in IP Telephony Networks Based on H.323

Methods for Lawful Interception in IP Telephony Networks Based on H.323 Methods for Lawful Interception in IP Telephony Networks Based on H.323 Andro Milanović, Siniša Srbljić, Ivo Ražnjević*, Darryl Sladden*, Ivan Matošević, and Daniel Skrobo School of Electrical Engineering

More information

Get Success in Passing Your Certification Exam at first attempt!

Get Success in Passing Your Certification Exam at first attempt! Get Success in Passing Your Certification Exam at first attempt! Exam : CCNT Title : Convergent Network Technologies Version : DEMO 1.Telecommunications is: A. The use of a telephone or similar equipment

More information

Lecture 21 ISDN Integrated Digital Network.

Lecture 21 ISDN Integrated Digital Network. Lecture 21 ISDN is an acronym for Integrated Services Digital Network. ISDN was developed to cater the needs of users who want high data rate, since conventional telephone line is not capable of providing

More information

Connection Services. Hakim S. ADICHE, MSc

Connection Services. Hakim S. ADICHE, MSc Connection Services Hakim S. ADICHE, MSc adiche@ccse.kfupm.edu.sa Department of Computer Engineering King Fahd University of Petroleum and Minerals Dhahran, Saudi Arabia Connection Services Different connectivity

More information

Voice and Delivery Data Networks

Voice and Delivery Data Networks Voice and Delivery Data Networks Chapter 11 Learning Objectives After reading this chapter, you should be able to: Identify the basic elements of a telephone system Describe the composition of the telephone

More information

Videoconferencing Glossary

Videoconferencing Glossary Videoconferencing Glossary Algorithm A set of specifications that define methods and procedures for transmitting audio, video, and data. Analog Gateway A means of connecting dissimilar codecs. Incoming

More information

Operation Manual Voice Overview (Voice Volume) Table of Contents

Operation Manual Voice Overview (Voice Volume) Table of Contents Operation Manual Voice Over (Voice Volume) Table of Contents Table of Contents Chapter 1 Voice Over... 1-1 1.1 Introduction to VoIP... 1-1 1.1.1 VoIP System... 1-1 1.1.2 Basic VoIP Call Flow... 1-2 1.1.3

More information

Dual-tone multi-frequency signaling

Dual-tone multi-frequency signaling Dual-tone multi-frequency signaling One of the few production telephone DTMF keypads with all 16 keys, from an Autovon Telephone. The column of red keys produces the A, B, C, and D DTMF events. Dual-tone

More information

Trunk Signaling. Figure 1 Subscriber Loop Signaling and Trunk Signaling

Trunk Signaling. Figure 1 Subscriber Loop Signaling and Trunk Signaling Signaling Overview Signaling is the step by step process of completing a telephone call. For example, when you make a telephone call, you lift the handset off of the telephone cradle (known as going off

More information

Chapter 8: The Telephone System

Chapter 8: The Telephone System Chapter 8: The Telephone System MULTIPLE CHOICE 1. DTMF stands for: a. Digital Telephony Multiple Frequency c. Dual-Tone Multifrequency b. Dial Tone Master Frequency d. Digital Trunk Master Frequency 2.

More information

ISDN. Raj Jain. Professor of CIS The Ohio State University Columbus, OH 43210 Jain@CIS.ohio-state.edu http://www.cis.ohio-state.edu/~jain/ Raj Jain

ISDN. Raj Jain. Professor of CIS The Ohio State University Columbus, OH 43210 Jain@CIS.ohio-state.edu http://www.cis.ohio-state.edu/~jain/ Raj Jain ISDN Professor of CIS Columbus, OH 43210 Jain@CIS.ohio-state.edu http://www.cis.ohio-state.edu/~jain/ 1 Overview History Interfaces and protocol layers Reference points Addressing 2 Integrated Digital

More information

Tech Note. Introduction. Definitions. What are FXS and FXO?

Tech Note. Introduction. Definitions. What are FXS and FXO? Tech Note What are FXS and FXO? Introduction The question What is the difference between FXS and FXO? is frequently asked by those deploying Patton Voice-over-Internet Protocol (VoIP) SmartNode solutions.

More information

(Refer Slide Time: 4:45)

(Refer Slide Time: 4:45) Digital Voice and Picture Communication Prof. S. Sengupta Department of Electronics and Communication Engineering Indian Institute of Technology, Kharagpur Lecture - 38 ISDN Video Conferencing Today we

More information

Internet Protocol (IP)/Intelligent Network (IN) Integration

Internet Protocol (IP)/Intelligent Network (IN) Integration Internet Protocol (IP)/Intelligent Network (IN) Integration Definition The convergence of the public switched telephone network (PSTN) and Internet protocol (IP) data networks promises exciting opportunities

More information

Network Technologies

Network Technologies Network Technologies Telephone Networks IP Networks ATM Networks Three Network Technologies Telephone Network The largest worldwide computer network, specialized for voice ing technique: Circuit-switching

More information

The Telephone Network

The Telephone Network ch02.qxd 10/17/00 9:14 AM Page 15 2 The Telephone Network INTRODUCTION This chapter provides an introduction to the telephone network, known in telephony circles, as The Network. Some people use the term

More information

ISDN. Raj Jain. Professor of CIS. The Ohio State University. Columbus, OH 43210 http://www.cis.ohio-state.edu/~jain/ Raj Jain

ISDN. Raj Jain. Professor of CIS. The Ohio State University. Columbus, OH 43210 http://www.cis.ohio-state.edu/~jain/ Raj Jain ISDN Professor of CIS Columbus, OH 43210 http://www.cis.ohio-state.edu/~jain/ 1 Overview History Interfaces and protocol layers Reference points Addressing 2 Integrated Digital Networks Integrated Both

More information

Module 2 Communication Switching. Version 1 ECE, IIT Kharagpur

Module 2 Communication Switching. Version 1 ECE, IIT Kharagpur Module 2 Communication Switching Lesson 2 Circuit Switching INSTRUCTIONAL OBJECTIVES GENERAL This lesson is aimed at developing the concept and application of circuit switching which is a very important

More information

PHILLIPS COUNTY TELEPHONE COMPANY PHILLIPS COUNTY COMMUNICATIONS, INC.

PHILLIPS COUNTY TELEPHONE COMPANY PHILLIPS COUNTY COMMUNICATIONS, INC. PHILLIPS COUNTY TELEPHONE COMPANY PHILLIPS COUNTY COMMUNICATIONS, INC. DEFINITIONS The Company utilizes the following definitions in its business and services: Access Code A sequence of numbers that, when

More information

WANs connect remote sites. Connection requirements vary depending on user requirements, cost, and availability.

WANs connect remote sites. Connection requirements vary depending on user requirements, cost, and availability. WAN Review A WAN makes data connections across a broad geographic area so that information can be exchanged between distant sites. This topic defines the characteristics of a WAN. WAN Overview WANs connect

More information

International Civil Aviation Organization

International Civil Aviation Organization International Civil Aviation Organization ATNICG WG/8-IP/3 AERONAUTICAL TELECOMMUNICATION NETWORK IMPLEMENTATION COORDINATION GROUP EIGHTH WORKING GROUP MEETING (ATNICG WG/8) Christchurch New Zealand 28

More information

._-_. Appendix 1 Page 22. CFDA To DID Intraswitch (8022)

._-_. Appendix 1 Page 22. CFDA To DID Intraswitch (8022) ._-. ----------------_. Appendix 1 Page 22 CFDA To DID Intraswitch (8022) Call Forwarding Don't Answer to DID Intraswitch allows calls to be forwarded to a DID number served from the same central office

More information

SIP Trunking and Voice over IP

SIP Trunking and Voice over IP SIP Trunking and Voice over IP Agenda What is SIP Trunking? SIP Signaling How is Voice encoded and transported? What are the Voice over IP Impairments? How is Voice Quality measured? VoIP Technology Confidential

More information

PART 17 - ISDN Services Original Sheet 16 SECTION 1 - ISDN Basic Rate Interface (BRI)

PART 17 - ISDN Services Original Sheet 16 SECTION 1 - ISDN Basic Rate Interface (BRI) PART 17 - ISDN Services Original Sheet 16 2. NATIONAL INTEGRATED SERVICES DIGITAL NETWORK (ISDN) DIRECT A. Description 1. National Integrated Services Digital Network (ISDN) Direct is a telecommunications

More information

Receiving the IP packets Decoding of the packets Digital-to-analog conversion which reproduces the original voice stream

Receiving the IP packets Decoding of the packets Digital-to-analog conversion which reproduces the original voice stream Article VoIP Introduction Internet telephony refers to communications services voice, fax, SMS, and/or voice-messaging applications that are transported via the internet, rather than the public switched

More information

8086 Telephony Training Systems

8086 Telephony Training Systems 8086 Telephony Training Systems LabVolt Series Datasheet Festo Didactic en 120 V - 60 Hz 01/2016 Table of Contents General Description 2 Topic Coverage 6 Features & Benefits 6 List of Available Training

More information

Mobile Wireless Overview

Mobile Wireless Overview Mobile Wireless Overview A fast-paced technological transition is occurring today in the world of internetworking. This transition is marked by the convergence of the telecommunications infrastructure

More information

Select Engineered Systems Field Bulletin: ATA and Evolving Terminology

Select Engineered Systems Field Bulletin: ATA and Evolving Terminology Select Engineered Systems Field Bulletin: ATA and Evolving Terminology December 2013 As the Cable industry (CATV) has evolved from Analog/RF to digital transmission methods, additional services such as

More information

White Paper: Voice Over IP Networks

White Paper: Voice Over IP Networks FREE FREE One One Hour Hour VoIPonline VoIPonline Seminar TM Seminar TM For additional information contact: Terry Shugart - tshugart@analogic.com http://www.analogic.com/cti TEL: 978-977-3000 FAX: 978-977-6813

More information

Signaling System 7 (SS7) Gateway Solution for Internet Access

Signaling System 7 (SS7) Gateway Solution for Internet Access Signaling System 7 (SS7) Gateway Solution for Internet Access Definition A signaling system 7 (SS7) gateway is an intelligent network (IN) based system that can be used in conjunction with network-access

More information

Integrate VoIP with your existing network

Integrate VoIP with your existing network Integrate VoIP with your existing network As organisations increasingly recognise and require the benefits voice over Internet Protocol (VoIP) offers, they stop asking "Why?" and start asking "How?". A

More information

Configuring the 930A for Common PBX Metallic Signaling Interfaces

Configuring the 930A for Common PBX Metallic Signaling Interfaces Product: 930A Communications Test Set APPLICATION NOTE # Configuring the 930A for Common PBX Metallic Signaling Interfaces TABLE OF CONTENTS Introduction...1 Primer...1 LOOP START...2 General...2 Trunk

More information

RESIDENTIAL PHONE FEATURES

RESIDENTIAL PHONE FEATURES RESIDENTIAL PHONE FEATURES User Guide Athens-Dec 9/10 Caller ID The Telephone display screen will show you the caller s name and telephone number, usually after the first complete ring. The service also

More information

Building a Scalable Numbering Plan

Building a Scalable Numbering Plan Building a Scalable Numbering Plan Scalable Numbering Plan This topic describes the need for a scalable numbering plan in a VoIP network. Dial Plans Dial plans contain specific dialing patterns for a user

More information

Signaling System 7 (SS7)

Signaling System 7 (SS7) Signaling System 7 (SS7) Definition Signaling System 7 (SS7) is an architecture for performing out-of-band signaling in support of the call-establishment, billing, routing, and information-exchange functions

More information

The Telephone Network

The Telephone Network The Telephone Network 1 2 PSTN public switched telephone network (PSTN) is the largest and most widespread communications network in the world For computer communications used to link remote sites of organisation

More information

Need for Signaling and Call Control

Need for Signaling and Call Control Need for Signaling and Call Control VoIP Signaling In a traditional voice network, call establishment, progress, and termination are managed by interpreting and propagating signals. Transporting voice

More information

/Amended by 26th resolution of 2009, 4th resolution of 2012, 39th resolution of 2014 of CRC respectively/

/Amended by 26th resolution of 2009, 4th resolution of 2012, 39th resolution of 2014 of CRC respectively/ Annex No.1 to the 25th resolution of the Communications Regulatory Commission, 2007 REGULATION ON VOICE OVER INTERNET PROTOCOL /Amended by 26th resolution of 2009, 4th resolution of 2012, 39th resolution

More information

CTS2134 Introduction to Networking. Module 07: Wide Area Networks

CTS2134 Introduction to Networking. Module 07: Wide Area Networks CTS2134 Introduction to Networking Module 07: Wide Area Networks WAN cloud Central Office (CO) Local loop WAN components Demarcation point (demarc) Consumer Premises Equipment (CPE) Channel Service Unit/Data

More information

WAN Technology. Heng Sovannarith heng_sovannarith@yahoo.com

WAN Technology. Heng Sovannarith heng_sovannarith@yahoo.com WAN Technology Heng Sovannarith heng_sovannarith@yahoo.com Introduction A WAN is a data communications network that covers a relatively broad geographic area and often uses transmission facilities provided

More information

Integration of Voice over Internet Protocol Experiment in Computer Engineering Technology Curriculum

Integration of Voice over Internet Protocol Experiment in Computer Engineering Technology Curriculum Integration of Voice over Internet Protocol Experiment in Computer Engineering Technology Curriculum V. Rajaravivarma and Farid Farahmand Computer Electronics and Graphics Technology School of Technology,

More information

LOCAL TELEPHONE SERVICE ADDENDUM to the. Carrier Account Master Service Agreement

LOCAL TELEPHONE SERVICE ADDENDUM to the. Carrier Account Master Service Agreement LOCAL TELEPHONE SERVICE ADDENDUM to the THIS LOCAL TELEPHONE SERVICE ADDENDUM ( Addendum ) shall be attached to and become a part of the ( Agreement ) by and between Electric Lightwave, LLC ( ELI ) and

More information

GW400 VoIP Gateway. User s Guide

GW400 VoIP Gateway. User s Guide GW400 VoIP Gateway User s Guide P/N: 956YD30001 Copyright 2006. All Rights Reserved. Document Version: 1.0 All trademarks and trade names are the properties of their respective owners. i Table of Contents

More information

Call Waiting. Cancel Call Waiting

Call Waiting. Cancel Call Waiting PhoneFeatures 1 Call Waiting Cancel Call Waiting 2 Three-Way Calling Personal Ringing 3 Speed Calling Call Transfer 4 Call Hold Call Forwarding 5 Call Forwarding Don t Answer Call Forwarding Busy Line

More information

With 360 Cloud VoIP, your company will benefit from more advanced features:

With 360 Cloud VoIP, your company will benefit from more advanced features: Voice over IP (VoIP) has emerged as the new leader in cost-effective standards based communications. 360 Cloud VoIP enables customers have the benefits of an Enterprise PBX for a fraction of the cost of

More information

Telecommunications, Networks, and Wireless Computing

Telecommunications, Networks, and Wireless Computing Objectives Telecommunications, Networks, and Wireless Computing 1. What are the features of a contemporary corporate telecommunications system? On what major technology developments are they based? 2.

More information

Darien Telephone Company Section 12 General Services Tariff Original Page 1 INT E GRA T ED SERVIC ES DI GI T A L NE T W O R K (ISDN) SERVI C E

Darien Telephone Company Section 12 General Services Tariff Original Page 1 INT E GRA T ED SERVIC ES DI GI T A L NE T W O R K (ISDN) SERVI C E Section 12 General Services Tariff Original Page 1 T ABL E O F C ONT E NTS 12.1 ISDN-B ASI C R A T E IN T E R F A C E SE R V I C E... 2 12.1.1 General 12.1.2 Abbreviations 12.1.3 Service Components 12.1.4

More information

Lecture overview. History of cellular systems (1G) GSM introduction. Basic architecture of GSM system. Basic radio transmission parameters of GSM

Lecture overview. History of cellular systems (1G) GSM introduction. Basic architecture of GSM system. Basic radio transmission parameters of GSM Lecture overview History of cellular systems (1G) GSM introduction Basic architecture of GSM system Basic radio transmission parameters of GSM Analogue cellular systems 70 s In the early 70 s radio frequencies

More information

Migrating from Circuit to Packet: The Business Case for IP Telephony. Or What s In it for Me?

Migrating from Circuit to Packet: The Business Case for IP Telephony. Or What s In it for Me? Migrating from Circuit to Packet: The Business Case for IP Telephony Or What s In it for Me? Even amidst the turmoil the telecommunications industry finds itself in, industry pundits are still expounding

More information

CONSULTATION. National Numbering Plan Review. A short Consultation issued by the Telecommunications Regulatory Authority 28 August 2007

CONSULTATION. National Numbering Plan Review. A short Consultation issued by the Telecommunications Regulatory Authority 28 August 2007 National Numbering Plan Review A short Consultation issued by the Telecommunications Regulatory Authority 28 August 2007 The address for responses to this document is: The General Director, Telecommunications

More information

WAN. Introduction. Services used by WAN. Circuit Switched Services. Architecture of Switch Services

WAN. Introduction. Services used by WAN. Circuit Switched Services. Architecture of Switch Services WAN Introduction Wide area networks (WANs) Connect BNs and LANs across longer distances, often hundreds of miles or more Typically built by using leased circuits from common carriers such as AT&T Most

More information

Tutorial on Signaling System 7 (SS7) Performance Technologies www.pt.com

Tutorial on Signaling System 7 (SS7) Performance Technologies www.pt.com Tutorial on Signaling System 7 (SS7) Performance Technologies Table of Contents Topic Page Overview...3 Signaling Links...3 Signaling Points...3 SS7 Signaling Link Types...4 SS7 Protocol Stack...6 Message

More information

PART 17 - ISDN Services 1st Revised Sheet 1 SECTION 2 - ISDN Primary Rate Interface (PRI) Cancels Original Sheet 1

PART 17 - ISDN Services 1st Revised Sheet 1 SECTION 2 - ISDN Primary Rate Interface (PRI) Cancels Original Sheet 1 PART 17 - ISDN Services 1st Revised Sheet 1 SECTION 2 - ISDN Primary Rate Interface (PRI) Cancels Original Sheet 1 1. ISDN PRIME SERVICE A. Description ISDN (Integrated Services Digital Network) Prime

More information

Introduction to Switching Systems

Introduction to Switching Systems 1 Introduction to Switching Systems 1.1. Introduction 1.2. Historical Development 1.3. Signal Characteristics 1.4. Elements of Communication Switching System 1.5. Criteria for the Design of Telecmmunication

More information

Terms VON. VoIP LAN WAN CODEC

Terms VON. VoIP LAN WAN CODEC VON Voice Over the Net. Voice transmitted over the Internet. That is the technical definition. Prescient Worldwide s product, called VON, means Voice Over Network as in ANY network, whether a client s

More information

Software Engineering 4C03 VoIP: The Next Telecommunication Frontier

Software Engineering 4C03 VoIP: The Next Telecommunication Frontier Software Engineering 4C03 VoIP: The Next Telecommunication Frontier Rudy Muslim 0057347 McMaster University Computing and Software Department Hamilton, Ontario Canada Introduction Voice over Internet Protocol

More information

VoIP for Radio Networks

VoIP for Radio Networks White Paper VoIP for Radio Networks Revision 1.0 www.omnitronicsworld.com In the early eighties, a communications protocol was created that allowed the research community to send data anywhere in the world

More information

Overview of WAN Connections Module 1

Overview of WAN Connections Module 1 Overview of WAN Connections Module 1 Objectives This module introduces the basic elements of WAN connections and describes the role each element plays in creating that connection. After completing this

More information

WAN Data Link Protocols

WAN Data Link Protocols WAN Data Link Protocols In addition to Physical layer devices, WANs require Data Link layer protocols to establish the link across the communication line from the sending to the receiving device. 1 Data

More information

VoIP Solutions Guide Everything You Need to Know

VoIP Solutions Guide Everything You Need to Know VoIP Solutions Guide Everything You Need to Know Simplify, Save, Scale VoIP: The Next Generation Phone Service Ready to Adopt VoIP? 10 Things You Need to Know 1. What are my phone system options? Simplify,

More information

VoIP Conferencing. The latest in IP technologies deliver the next level of service innovation for better meetings. Global Collaboration Services

VoIP Conferencing. The latest in IP technologies deliver the next level of service innovation for better meetings. Global Collaboration Services Global Collaboration Services VoIP Conferencing The latest in IP technologies deliver the next level of service innovation for better meetings. ENERGIZE YOUR CONNECTIONS Table of Contents > > Contents...

More information

Inbound Routing with NetSatisFAXTion

Inbound Routing with NetSatisFAXTion Inbound Routing with NetSatisFAXTion Routing Terms DID Direct Inward Dialing (DID) is a service of a local phone company (or local exchange carrier) that provides a block of telephone numbers for calling

More information

PART 17 - ISDN Services 5th Revised Sheet 1 SECTION 2 - ISDN Primary Rate Interface (PRI)

PART 17 - ISDN Services 5th Revised Sheet 1 SECTION 2 - ISDN Primary Rate Interface (PRI) PART 17 - ISDN Services 5th Revised Sheet 1 1. ISDN PRIME SERVICE A. DESCRIPTION ISDN (Integrated Services Digital Network) Prime is a digital business service that provides PBX equipment and host computer

More information

8 Wide Area Network (WAN)

8 Wide Area Network (WAN) Wide Area Network (WAN).1 Introduction Objectives.2 Why need a WAN?.3 Switching Techniques.3.1 Circuit switching network.3.2 Packet switching Network.3.2.1 How Packet Switching Network Works?.3.2.2 Datagram

More information

Parlay i60 - Application

Parlay i60 - Application Parlay i60 ISDN Access Multiplexer with advanced call routing features Solutions for Carriers & Service Providers Parlay i60 ISDN Access Multiplexer a miracle in terms of possible applications Cost efficient

More information

Call Setup and Digit Manipulation

Call Setup and Digit Manipulation Call Setup and Digit Manipulation End-to-End Calls This topic explains how routers interpret call legs to establish end-to-end calls. End-to-End Calls IP Telephony 2005 Cisco Systems, Inc. All rights reserved.

More information

CS 5516 Computer Architecture Networks

CS 5516 Computer Architecture Networks Lecture 11: ISDN & ATM CS 5516 Computer Architecture Networks VA Tech Prof. Roy M. Wnek History of ISDN Traditionally, local loop connectivity has been with an analog signal on copper Inefficient, prone

More information

Converged Voice Service Summary

Converged Voice Service Summary SERVICE DELIVERY OVERVIEW Zayo Enterprise Networks (ZEN) offers a managed converged voice and Internet solution for businesses owning and managing a premise-based KTS or PBX system. Voice and Internet

More information

Attendant Console A VoIP feature, this allows a user to monitor another user's phone using an attendant application

Attendant Console A VoIP feature, this allows a user to monitor another user's phone using an attendant application ADSL Asymmetrical Digital Subscriber Line number. Alternate Numbers A VoIP feature, this allows a user to have alternate phone numbers and extensions. Anonymous Call Rejection With Caller Id Combines anonymous

More information

Network+ Guide to Networks 6 th Edition. Chapter 7 Wide Area Networks

Network+ Guide to Networks 6 th Edition. Chapter 7 Wide Area Networks Network+ Guide to Networks 6 th Edition Chapter 7 Wide Area Networks Objectives Identify a variety of uses for WANs Explain different WAN topologies, including their advantages and disadvantages Compare

More information

DIGITAL TELEPHONE CALLING FEATURES. Anonymous Call Rejection. Auto Recall. Call Forwarding. Automatic Recall (AR) Automatic Callback (AC)

DIGITAL TELEPHONE CALLING FEATURES. Anonymous Call Rejection. Auto Recall. Call Forwarding. Automatic Recall (AR) Automatic Callback (AC) 1 Anonymous Call Rejection Anonymous Call Rejection (ACR) enables you to automatically block calls from parties whose numbers are marked Private. When subscribed and activated, this feature routes incoming

More information

Converged TDM and IP- Based Broadband Solutions White Paper. OnSite OS-10 Multi-Service over SDH Provisioning

Converged TDM and IP- Based Broadband Solutions White Paper. OnSite OS-10 Multi-Service over SDH Provisioning Converged TDM and IP- Based Broadband Solutions White Paper OnSite -10 Multi-Service over SDH Provisioning Copyright Copyright 2009, Patton Electronics Company. All rights reserved. Printed in the USA.

More information

SMALL BUSINESS PHONE SYSTEMS OFFER BIG BUSINESS ADVANTAGES

SMALL BUSINESS PHONE SYSTEMS OFFER BIG BUSINESS ADVANTAGES SMALL BUSINESS PHONE SYSTEMS OFFER BIG BUSINESS ADVANTAGES Investing in a phone system is an important step for any small business. Your decision to sign up for small business phone service service should

More information