Public Switched Telephone Network (PSTN)
Session Initiation Protocol (SIP)
Learn IT in 10 easy steps
Directions: Read steps 1-8 and their related links. Use the glossary to look up any terms you do not know. When you're done, go to step 10 and take a quiz to see how much you've learned!
First things first… VoIP defined
VoIP (Voice over IP - that is, voice delivered using the Internet Protocol) 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).
2. Let's look at the difference between VoIP and voice and data convergence
VoIP specifically refers to sending voice traffic over an IP (Internet Protocol) network and does not integrate data applications. Voice and data convergence refers to sending both voice and data (such as LAN traffic) over any data network (typically an IP network, frame relay network or ATM network).
IP telephony refers to any "telephone" type service carried over IP and includes voice, fax, video and even text messaging. VoIP involves only voice transmission.
3. Let's take a look at the standards
H.323 is a standard approved by the International Telecommunication Union (ITU) in 1996 to promote compatibility in videoconference transmissions over IP networks. H.323 was originally promoted as a way to provide consistency in audio, video and data packet transmissions in the event that a local area network (LAN) did not provide guaranteed service quality (QoS). Although it was doubtful at first whether manufacturers would adopt H.323, it is now considered to be the standard for interoperability in audio, video and data transmissions as well as Internet phone and Voice over IP (VoIP) because it addresses call control and management for both point-to-point and multipoint conferences as well as gateway administration of media traffic, bandwidth and user participation.
SIP (Session Initiation Protocol) 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. Like HTTP or SMTP, SIP works in the Application layer of the Open Systems Interconnection (OSI) communications model. The Application layer is the level responsible for ensuring that communication is possible. SIP can establish multimedia sessions or Internet telephony calls, and modify or terminate them.
H.323 and SIP are often compared and do compete with each other for VoIP services. H.323 has been the early leader in this market so it is very popular, but SIP is arguably becoming the de facto standard for VoIP.
4. Getting to know VoIP regulations
Unfortunately, the biggest challenge to the total adoption of VoIP isn't the complex technology, or the lack of experienced implementers, or even compelling business cases -- it's regulatory hoopla. VoIP is simply illegal in an astonishing number of countries, while the rest are mired in enough red tape to often negate the cost savings.
Former chairman of the Federal Communications Commission, Michael Powell, strongly argues that new communications technologies should not be subjected to federal and state regulations. However, there is staunch opposition from several states to regulate VoIP as a traditional telephone service, a move that many fear would stifle its potential.
We're keeping track of developments and will update this report as we learn more.
5. Does your network have what it takes?
One of the biggest challenges in implementing a VoIP solution is making sure you have all the necessary components. This can be especially daunting if you're new to VoIP.
Among the things you can do before you even pick a vendor are:
6. Here's a look at some top VoIP players.
7. Let's learn how to evaluate IP telephony products
If you've decided to implement an IP telephony network, but you haven't decided on a vendor yet, you're probably planning to evaluate a lot of IP telephony hardware and software in the near future. You've got a lot of questions to answer. These include concerns about the hardware and software compatibility with your existing network, and of course, you want to listen to actual phone calls to hear how it sounds for yourself.
You also want to verify interoperability between a number of vendors and product lines.
All of this may be easier said than done. You get some demo equipment from your salesmen, but if you don't already have a network set up, what good is it? If you're trying to set up all the equipment at once and you have issues, it's hard to know which product is misconfigured or at fault. These and other issues can make evals almost pointless.
8. Let's see who's offering VoIP training
Acquiring the skills to be successful with voice over IP is challenging for most people because it requires a broad knowledge-base in two domains (voice and data networking), plus a functional understanding of the protocols and hardware that connect these two areas (thus the name "convergence").
Fortunately, most people interested in this field start with a reasonably solid grasp of one or the other (voice or data networking). But many people don't know where to begin to find out what they don't know.
numerous organizations offer
certs in this area, including the likes of Alcatel, Cisco (one of the Cisco qualified specialist
credentials focuses on IP telephony) and Nortel, among others.
9. Voice over IP tips
Browse our collection of Voice over IP tips for hands-on advice on preparing for VoIP implementations, as well as information on deployment and maintenance.
This was first published in March 2005