Learning Guide: Voice over IP basics
This guide contains all the VoIP basics and essentials you will need when implementing an IP telephony network.
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VoIP (Voice over Internet Protocol)
This guide presents VoIP articles, tutorials, examples, tips, tools, white papers, expert advice and more to pump up your VoIP know-how quickly.
TABLE OF CONTENTS
What is VoIP?
How does VoIP work?
Circuit switching vs. packet switching
H.323 and SIP
PBXs, IP-PBXs and hybrid systems
Advantages and disadvantages
Hosted vs. in-house VoIP
Regulatory issues/E911
Securing VoIP
QoS
More Learning Guides
What is VoIP?
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VoIP (Voice over IP ) is a term used in IP telephony for a set of facilities for managing the delivery of voice information using the Internet Protocol (IP). In general, this means sending voice information in digital form in discrete packets rather than in the traditional circuit-committed protocols of the public switched telephone network (PSTN). This guide will help you understand the technology behind VoIP. In addition, this guide delves into key VoIP issues such as; security, regulations, advantages and disadvantages, outsourcing and QoS.
- Glossary definition: VoIP (WhatIs.com)
- Glossary definition: VoIP phone (WhatIs.com)
- Glossary definition: IP telephony (WhatIs.com)
- Glossary definition: PSTN (WhatIs.com)
- Glossary definition: IP (WhatIs.com)
- Glossary definition: ATM (WhatIs.com)
- Guide: Learn IT in 10 easy steps: VoIP (SearchEnterpriseVoice.com)
- Chapter download: Taking charge of your VoIP project (SearchEnterpriseVoice.com)
- White paper: Selecting VoIP for your enterprise (Global Knowledge)
- Webcast: How your business can take full advantage of VoIP (3Com Corporation)
- Quiz: When is it worthwhile to move to VoIP? (Tom Pisello)
- Tip: 2005 promises yet another 'Year of VoIP' (SearchEnterpriseVoice.com)
- Tip: Introduction to Internet telephony (SearchEnterpriseVoice.com)
- Tip: Seven steps to successful VoIP (SearchEnterpriseVoice.com)
- Article: Voice over what? (SearchEnterpriseVoice.com)
How does VoIP work?
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VoIP works by converting your analog voice into data packets (digital format), sending them over your existing data network and reconverting them to voice at the destination. The benefit of a digital format is that it can be controlled. It can be routed, modified, condensed, expanded and saved. Digital signals are also more noise tolerant than analog. This section will help you to understand the basic processes and functionalities of VoIP.
- Expert advice: What are the steps involved in designing a VoIP network? (SearchEnterpriseVoice.com)
- Tip: IP telephony implementation planning (SearchEnterpriseVoice.com)
- Tip: VoIP:The face of the new network police (SearchEnterpriseVoice.com)
- Chapter download: Implementing Voice over IP- Chpt 6: VoIP Deployment in Enterprises (SearchEnterpriseVoice.com)
- Web resource: IP-enabled services (Federal Communications Commission)
- Web resource: Simple explanation of VoIP (Wilco Telephony)
- Web resource: VoIP 101 (VoIP Now)
- Web resource: VoIP how to (Roberto Arcomano Berto)
Circuit switching vs. packet switching
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Circuit switching was developed for analog-based telephone systems. Circuit switching has been used extensively for the public switched telephone network (PSTN). In circuit switching, users have exclusive use of a connection until the conversation is over and the connection is released. In packet switching, messages are divided into packets, and many users share access to a circuit by taking turns putting their packets onto the channel. Breaking communication down into packets increases capacity. This type of communication between sender and receiver is known as connectionless (rather than dedicated). Most traffic over the Internet uses packet switching.
- Glossary definition: packet (WhatIs.com)
- Glossary definition: packet-switched (WhatIs.com)
- Glossary definition: circuit switched (WhatIs.com)
- Glossary definition: TCP (WhatIs.com)
- Glossary definition: TCP/IP (WhatIs.com)
- Tip: Bulletproof IP telephony deployment, Part 1 (SearchEnterpriseVoice.com)
- Tip: Bulletproof IP telephony deployment, Part 2 (SearchEnterpriseVoice.com)
- Tip: Bulletproof IP telephony deployment, Part 3 (SearchEnterpriseVoice.com)
- Tip: VoIP analysis (SearchEnterpriseVoice.com)
- Tip: Lowering packet size (SearchEnterpriseVoice.com)
- Tip: Avaya's management enhances reliability, sets stage for next-generation VoIP (SearchEnterpriseVoice.com)
- Tip: Duties of an IP telephony gateway when integrating VoIP and the PSTN (SearchEnterpriseVoice.com)
- Tip: Probing to maximize MTU efficiency and deliver QoS (SearchEnterpriseVoice.com)
- Article: Alcatel's new switches styled for convergence (SearchEnterpriseVoice.com)
- Article: Extreme switch aims to cut out the middleman (SearchEnterpriseVoice.com)
- Web resource: Circuit switching vs. packet switching (Cram Session)
- Web resource: DTM fundamentals and network solutions (International Engineering Consortium)
- Web resource (PDF): Making the packet connection with TDM-over-IP (Analog Zone)
- Web resource: Packet versus circuit switching (ZVON.org)
H.323 and SIP
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The Session Initiation Protocol (SIP) is an Internet Engineering Task Force (IETF) standard protocol for initiating an interactive user session that involves multimedia elements such as video, voice, chat, gaming, and virtual reality. H.323 is a standard approved by the International Telecommunication Union (ITU) in 1996 to promote compatibility in videoconference transmissions over IP networks.
- Glossary definition: SIP (WhatIs.com)
- Glossary definition: H.323 (WhatIs.com)
- Glossary definition: SIMPLE (WhatIs.com)
- Learning Guide: SIP (SearchEnterpriseVoice.com)
- Expert advice: What is the VoIP future protocol? (Carrie Higbie)
- Expert advice: Difference between H.323 and SIP (Patrick Ferriter)
- Expert advice: SIP advantages and disadvantages (Carrie Higbie)
- Q & A: SIP to grow leaps, out of VoIP bounds (SearchEnterpriseVoice.com)
- Featured topic: Understanding SIP (SearchEnterpriseVoice.com)
- Tip: VoIP and protocols (Sudha Rani)
- Tip: SIP, don't gulp (SearchEnterpriseVoice.com)
- Article: VoIP experts savor SIP's potential (SearchEnterpriseVoice.com)
- Article: Is SIP a king with no kingdom? (SearchEnterpriseVoice.com)
- Article: SIP promises sweet taste of interoperability (SearchEnterpriseVoice.com)
- Article: Telephony architecture enters a new era (SearchEnterpriseVoice.com)
- Chapter download: IP Telephony Demystified - Chapter 4, IP telephony protocols (SearchEnterpriseVoice.com)
- Chapter download: IP Telephony: Deploying VoIP protocols - Chpt. 3: SIP (SearchEnterpriseVoice.com)
- Web resource: H.323 standards (openh323.org)
- Web resource: H.323 overview (International Engineering Consortium)
- Web resource: H.323 forum (H.323 Forum)
- Web resource: VOIP protocols overview (Javvin Technologies, Inc.)
- Web resource: SIP Forum (SIP Forum)
- Web resource: SIP charter (IETF)
PBXs, IP-PBXs and hybrid systems
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A PBX is a telephone system that switches calls between enterprise users on local lines while allowing all users to share a certain number of external phone lines. The main purpose of a PBX is to save the cost of requiring a line for each user to the telephone company's central office. An IP PBX is a private branch exchange that switches calls between VoIP users on local lines while allowing all users to share a certain number of external phone lines. A typical IP PBX can also switch calls between a VoIP user and a traditional telephone user.
Many major vendors are offering hybrid voice systems that combine elements of VoIP and public switched telephone network (PSTN) systems. These new hybrid systems may give enterprises an opportunity to benefit from VoIP cost savings by combining the traditional telephony hardware with new technologies.
- Glossary definition: PBX (WhatIs.com)
- Glossary definition: IP-PBX (WhatIs.com)
- Expert advice: What are IP PBXs? (Patrick Ferriter)
- Article: A hazy future for the IP-PBX (SearchEnterpriseVoice.com)
- Article: Opportunities abound for hybrid voice systems (SearchEnterpriseVoice.com)
- Article: Call director fuses landline, VoIP calls (SearchEnterpriseVoice.com)
- Tip: Hosted PBX lets small businesses act big (SearchEnterpriseVoice.com)
- Web resource: IP PBX architecture (VOIP-info.org)
- Web resource: List of IP PBX/IP Centrex solutions (iptelephony.org)
Advantages and disadvantages
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VoIP technologies can reduce telecommunication and networking costs and offer new voice capabilities. However, it is important that you understand the advantages and disadvantages of VoIP before you begin an implementation. Some advantages include; reduction of intra-office toll charges, lower hardware costs, productivity benefits for remote and traveling workers, improved security and reduced system downtime. Some of the risks involved with a VoIP project can include; quality of service/performance issues, cost and resources needed for user and administrative training and proprietary vs. open systems interoperability. This section takes a closer look at the good, bad and ugly of VoIP.
- Quiz: When is it worthwhile to move to VoIP? (Tom Pisello)
- Tip: Before deploying VoIP consider this (SearchEnterpriseVoice.com)
- Expert webcast: Developing a true cost model for VoIP (SearchEnterpriseVoice.com)
- Expert advice: How do I know if VoIP is right for my business? (Tom Pisello)
- Expert advice: Pros and cons of VoIP (Tom Pisello)
- Case study: TCF Financial Corp. (SearchEnterpriseVoice.com)
- Case study: Johns Hopkins Bloomberg School of Public Health (SearchEnterpriseVoice.com)
- Article: Famous zoo roars over VoIP benefits (SearchEnterpriseVoice.com)
- Article: Adopters highlight complex decisions behind VoIP (SearchEnterpriseVoice.com)
- Article: Experts warn of too much static in VoIP-IM combo (SearchEnterpriseVoice.com)
- Article: VoIP 2005: Better watch what you say (SearchEnterpriseVoice.com)
- Article: Vendors 'lying' about VoIP cost savings (SearchEnterpriseVoice.com)
- Article: VoIP can cut costs, but capable of much more (SearchEnterpriseVoice.com)
- Web resource: A simple guide to VoIP advantages and disadvantages (TelCon Associates, Inc.)
- Web resource: VoIP advantages (SearchNetworking.com)
- Web resource: VoIP's benefits come with emergency drawbacks (eWeek)
- Web resource: VoIP: Is it ready for primetime? (Inc.com)
Hosted vs. in-house VoIP
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Many carriers are now offering low-maintenance hosted VoIP services for enterprises. Is hosted VoIP right for your company? There are many things to consider when making the choice between hosted and in-house VoIP. Quality of service (QoS) issues, hardware stability, network monitoring and latency are all very important factors to look at. This section will help you better understand the pros and cons of both options.
- Glossary definition: outsourcing (WhatIs.com)
- Expert advice: Why should we use a hosted voice service? (John Blake)
- Article: IDC: Bright future for hosted VoIP (SearchEnterpriseVoice.com)
- Article: Making the case for VoIP outsourcing (SearchEnterpriseVoice.com)
- Article: Hosted VoIP has its advantages, risks (SearchEnterpriseVoice.com)
- Featured topic: Hosted VoIP (SearchEnterpriseVoice.com)
- Web resource: Presentation on hosted IP services vs. managed IP services (Broadsoft)
- Web resource: Hosted IP voice will storm the enterprise (eWeek)
- Web resource: The slow rise of managed voice services (Outsourcing Pipeline)
- Web resource: Managing security issues in hosted IP telephony (btnaccess)
- Web resource: Hosted voice services (Telecommunications Magazine )
Regulatory issues/E911
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In many countries, VoIP is illegal. In many others (including the United States) telecom regulations are changing faster than you can say 911. Recently, the Supreme Court ruled to uphold FCC regulations permitting cable operators to block rivals from using their infrastructures. This could hurt VoIP providers and increase costs significantly. In addition, the FCC has set a mandate for VoIP providers to get E911 services up and running soon. This section will help you sort through the intricate web of VoIP regulations.
- Glossary definition: E911 (WhatIs.com)
- Expert advice: Impact of VoIP E911 (Patrick Ferriter)
- Tip: The trouble with 911 and VoIP (SearchEnterpriseVoice.com)
- Article: VoIP regulatory issues concern Interop attendees (SearchEnterpriseVoice.com)
- Article: VoIP industry preps for regulatory battles, new competition (SearchEnterpriseVoice.com)
- Article: Industry coalition seeks to head off VoIP 911 requirements (SearchEnterpriseVoice.com)
- Article: Enterprises answer FCC's 911 call (SearchEnterpriseVoice.com)
- Featured topic: Could VoIP kill? (SearchEnterpriseVoice.com)
- Web resource: VoIP regulations enter a perfect storm (eWeek)
- Web resource: Get to know VoIP regulations (SearchNetworking.com)
- Web resource: VoIP regulations goes up in flames (VoIP Now)
- Web resource: VoIP regulations kick in (TechWeb)
Securing VoIP
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Deploying effective VoIP security is challenging. Since telephony traffic must travel over the IP network between gateways, stations, servers and proxies, there are plenty of places to attack. The list of possible threats includes; toll fraud, impersonation, hijacking of calls, session replay, media tampering, denial of service and SPIT. This section will help you avoid some security pitfalls.
- Glossary definition: SPIT (WhatIs.com)
- Glossary definition: denial of service (WhatIs.com)
- VoIP Security Resource Guide (SearchEnterpriseVoice.com)
- Expert advice: How will a service provider ensure security and QoS? (John Blake)
- Tip: Employ fuzzing to test VoIP security (SearchEnterpriseVoice.com)
- Tip: Stolen voices: The challenge of securing VoIP (SearchEnterpriseVoice.com)
- Tip: Don't forget to secure the signaling (SearchEnterpriseVoice.com)
- Tip: M2M issues in VoIP security (SearchEnterpriseVoice.com)
- Tip: Mitigating VoIP deployment risks with route analytics (SearchEnterpriseVoice.com)
- Article: VoIP could bring new security threats (SearchEnterpriseVoice.com)
- Article: VoIP security details make or break implementation (SearchEnterpriseVoice.com)
- Article: Gartner underscores five overblown threats (SearchEnterpriseVoice.com)
- Article: Can VoIP ever be as secure as Ma Bell's creation? (SearchEnterpriseVoice.com)
- Article: VoIP security, 'spit' concern experts (SearchEnterpriseVoice.com)
- Article: VoIP demands more from a firewall (SearchEnterpriseVoice.com)
- Q & A: Avoiding a VoIP security 'judgment day' (SearchEnterpriseVoice.com)
- Whitepaper: What to look for in VoIP security (Ranch Networks)
QoS
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A big component of VoIP infrastructure is effectively deploying a Quality of Service (QoS) model. QoS is the idea that transmission rates, error rates and other characteristics can be measured, improved, and to some extent, guaranteed in advance. QoS is of particular concern for the continuous transmission of high-bandwidth video and multimedia information. There are many ways to ensure QoS. This section will help you decide which QoS method is right for you.
- Glossary definition: QoS (WhatIs.com)
- Glossary definition: bandwidth (WhatIs.com)
- Expert advice: Measuring quality of service (Patrick Ferriter)
- Expert advice: QoS in a VoWLAN (Joel Vincent)
- Expert advice: Challenges of QoS for large IP networks (Carrie Higbie)
- Expert advice: How successful is E-Model, a tool for measuring QoS for VoIP? (Patrick Ferriter)
- Tip: VoIP product development issues (SearchEnterpriseVoice.com)
- Tip: Elements of VoIP QoS (SearchEnterpriseVoice.com)
- Tip: Policing and shaping within QoS (SearchEnterpriseVoice.com)
- Tip: QoS classification and marking for VoIP infrastructures (SearchEnterpriseVoice.com)
- Tip: A closer look at QoS components (SearchEnterpriseVoice.com)
- Tip: Tools for VoIP planning, monitoring and management (SearchEnterpriseVoice.com)
- Tip: Link efficiency within QoS (SearchEnterpriseVoice.com)
- White paper: Latency and QoS for Voice over IP (SANS Institite)
- White paper: VoIP Quality of Service (QoS) Testing (Ixia Communications)
More Learning Guides
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Check out this collection of related learning tools and guides.
- Learning Guide: SIP (SearchEnterpriseVoice.com)
- VoIP Security Resource Guide (SearchEnterpriseVoice.com)
- Learn IT in 10 easy steps: VoIP (SearchEnterpriseVoice.com)
- Firewall Resource Guide (SearchNetworking.com)
- Guide to network performance management (SearchNetworking.com)
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