ip telephony
18 ResultsDictionary
IP telephony
The two-way transmission of voice over a packet-switched IP network, which is part of the TCP/IP protocol suite. The terms "IP telephony" and "voice over IP" (VoIP) are synonymous. However, the...
Dictionary
Definition: IP telephony
The two-way transmission of voice over a packet-switched IP network, which is part of the TCP/IP protocol suite. The terms "IP telephony" and "voice over IP" (VoIP) are synonymous. However, the term VoIP is widely used for the actual services offered (see VoIP for more details), while IP telephony often refers to the technology behind it. In addition, IP telephony is an umbrella term for all real-time applications over IP, including voice over instant messaging (IM) and videoconferencing.
Starting in the late 1990s, the Internet and its TCP/IP protocol suite began to turn the data communications and telephone industry upside down. IP has become the universal transport for almost all data and video communications worldwide. It is increasingly becoming the infrastructure for voice traffic as well. Today, every communications carrier has built or is using an IP backbone for some or all of its voice services. In addition, large enterprises are either already using IP for some amount of internal voice traffic or have plans to implement it or create test beds.
Data Over Voice Became Voice Over Data
Data was first transmitted over telephone networks, starting in the 1960s, and by the late 1980s, data routinely traveled over digital voice circuits. By the 1990s, the majority of worldwide communications traffic had changed from voice to data, and as IP networks began to flourish, the economics of using IP for voice began to emerge.
Although the backbone of the global telephone network had been converted to digital for some time, the circuit-switched nature of the public switched telephone network (PSTN) is wasteful. Even though one person talks and the other listens, both "to" and "from" channels are always dedicated. In addition, newer voice codecs cut the digital requirement from the traditional 64 Kbps (PCM) down to 8 Kbps with respectable quality. Thus, the bandwidth requirement for voice on an IP network is 1/16th that of the PSTN's dedicated, digital circuits.
Varying Quality
Starting in the mid-1990s, advertiser-supported, free telephone service from PC to PC or between phones and PCs using the public Internet became popular, especially for international calls. Call quality over the Internet can be erratic because the Internet provides no guarantee of quality of service (QoS). However, when an organization has control over its network, quality can be excellent. Private enterprises with their own IP networks, as well as major telcos and IP telephony carriers that have developed IP backbones, can provide voice quality that competes with the traditional PSTN.
Transport and Signaling
IP telephony uses two protocols: one for transport and another for signaling. Transport is provided by UDP over IP for voice packets and either UDP or TCP over IP for signals. Signaling commands that establish and terminate the call as well as provide special features such as call forwarding, call waiting and conference calling are defined in a signaling protocol such as H.323, SIP, MGCP or MEGACO (see IP telephony signaling protocol).
The integration of packet-switched IP with the traditional SS7-based telephone system is a complex undertaking with numerous protocols competing for attention. See ITXC and IP on Everything.
Integrating IP Telephony with the PSTN
This illustration shows the interaction between the traditional telco system and IP carriers, which are often one and the same. In order to understand the flow between these devices, it is important to note the difference between voice packets (blue lines) and signaling (red lines). (Illustration assistance courtesy of GNP Computers and Pulver.com.)
Not Quite IP Telephony
We can be certain that they didn't have the IP protocol in mind when they set up this telephone switchboard in 1882. It was used to switch phone calls between all the lawyers in Richmond, Virginia. (Image courtesy of AT&T.)
THIS DEFINITION IS FOR PERSONAL USE ONLY
All other reproduction is strictly prohibited without permission from the publisher.
© 1981-2010 The Computer Language Company Inc. All rights reserved.
Sponsored White Papers, Webcasts & Resources
-
Visibility, Alignment, & Optimization, Part III: Workforce Optimization
Check out this white paper to learn more about using human resource management to help align and optimize your workforce. Make sure your company is running on all cylinders.
-
Want to customize your company's caller ID? Here's one way.
IP telephone services company YouMail helps small businesses update the information displayed when they call or leave a message.
-
The best VoIP solution is ...
Businesses looking to implement a new VoIP solution or expand their existing investments are certainly spoiled for choice, and the benefits are not only available to the big spenders.
-
EU to investigate VoIP tapping
The European Union's Judicial Co-Operation Unit is looking at how to intercept calls made over services such as Skype, at the urging of Italy's anti-Mafia directorate
-
VoIP-builder tool Ribbit: has potential, but manage your boasting, please
In the IP Telephony space over the last several days, everybody's been talking about Ribbit. So I guess I should join the chorus. As you can see by the graphic, Ribbit's appealing value...
-
Should Skype and Vonage adapt or die?
Network World columnist Mark Gibbs expresses his wish that Internet telephony providers Skype and Vonage "die." Gibbs expresses this rather inelegant wish in large measure because both services...
-
-
3Com fills SMB niches with new IP Telephony products
Conversations I had with 3Com executives last week previewed some imminent rollouts of VoIP-enabling equipment for SMBs (Small to Medium Size Businesses between 5 and 200 users. Officially...
-
BT launches secure, hosted IP telephony
An alliance with Nortel has produced a certified, hosted service for large corporations and government institutions.
-
Skype troubleshooting tips: just one of many 'Net telephony eHows
In the first Internet boom, the website eHow was an online community of experts who posted some 15,000 step-by-step how-to articles before eHow crashed and burned back around 2001. For four...
-
Avaya, Cisco, Nortel tech chiefs on enterprise IP telephony apps in the oven
I'm sitting here in the audience at VoiceCon in San Francisco, checking out the CTO Roundtable. Line-up: Mun Yuen Leong, CTO of Avaya; Phil Edholm, CTO & VP, Enterprise Network Architecture,...
-
The green side of IP telephony
Up until two months ago, I was a horrible carbon dioxide offender. No excuses, really, other than the fact that my daily commute took me over two bridges from my New Jersey home out to Long...
-
Study: speciality IP telephony management tools best for enterprise VoIP costs
In Network World, Nemertes Research executive vice president and senior founding partner Robin Gareiss provides highlights of a study that quantifies the cost savings of specialty IP telephony...
-
Enterprises with multi-vendor IP telephony need single-tool management
I've just finished reading a May, 2007 white paper entitled Multi-vendor IP telephony management: challenges and solutions. From performance-management solutions provider Prognosis, the nine-page...
-
Net telephony's mainstream struggle
BellSouth's director of Converged Services, Steve Zimba, told attendees at the VON conference in San Jose that many residential customers are still wary of VoIP. CNET News.com reporter Marguerite...
-
Estonia's wired world
Looking for the most wirelessly hip, jacked in, "efficient" government around? Try Estonia, says the Economist. If only Lenin had known about Wi-Fi ...
-
Managing VoIP and IP Telephony
IP telephony is finally experiencing an inflection in its growth among large organizations. Intense attention is being directed toward the technology itself, but many risk their services by...
-
Networking for Voice, Video, and Data Integration
Enterprises continue to plan and evaluate the convergence of corporate communications over the IP infrastructure. IT organizations (ITOs) must pay close attention to the readiness of the...
-
Framework for an IP Telephony Decision
As organizations strategize for infrastructure consolidation, IP telephony discussions are compulsory. Guidelines for a decision in favor of IP telephony must include infrastructure readiness,...
-
IP telephony meets instant messaging
The next wave of improved productivity is the merging of IP telephony, instant messaging, e-mail, conferencing and other business applications. Siemens' OpenScape 1.0 shows where this...
Additional Results
-
Jay Leno uses indie YouTube video; NBC gets it taken down
Internet outcry rises after Jay Leno uses a YouTube video without permission and NBC removes it with a copyright claim takedown.
-
How to effectively protect your IP with a non-compete clause
Losing an employee can mean valuable know-how, trade secrets, code or algorithms walking out the door.
The best of ZDNet, delivered
ZDNet Newsletters
Get the best of ZDNet delivered straight to your inbox
Vendor Showcase
Facebook Activity
