IP Telephony and VoIP Tutorial


Welcome to the RFC IP Telephony and IP Telephony and VoIP Technology tutorial. This tutorial includes information helpful in deciding how best to take advantage of IP Telephony and VoIP technology in a business environment. The modules below are a tutorial on the basics of IP Telephony and VoIP. By reading through the tutorial, you will become more familiar with the terminology and technology.

Don't let the terms confuse you. IP Telephony is the term we use to describe the telecommunications application that provides the PBX services for your business. The IP Telephony application in a business environment is sometimes called an IP PBX. VoIP is the technology that puts voice into packets so it can be used on a Data Network.

Principles of VoIP

VoIP converts voice into data and sends the voice packets over the network. These packets get mixed with other voice and data packets and are reassembled into voice by an endpoint device (telephone). The result is a telephone call. When the network is well designed, the quality is as good as or better than that of the traditional public switched telephone network (PSTN).

IP Telephony and VoIP systems work by using standard protocols to communicate. The major protocols to consider in a business communications system will be largely invisible to the users, and most likely result in the same application and quality. The thing to keep in mind with standards is what protocol will provide the richest application and the most interoperability. SIP (Session Initialization Protocol) is the most promising standard and is most widely adopted. Using SIP based telephones that adhere to open standards provide you with a great degree of investment protection since the phones can be used with any SIP based IP PBX.

An IP Telephony system consists of several components. There are the endpoints, also known as telephones. These can be either an IP telephone or a soft-phone residing on a PC. The role of an IP telephone is identical to that of a traditional telephone. An IP telephone connects directly to a LAN instead of a traditional telephone connection. The soft-phone is a program that runs on your PC and performs all of the same functions of a telephone using your multimedia speakers and microphone plus video in some instances. In an IP PBX, the endpoints are very intelligent.

To control routing calls to and from endpoints there is an IP PBX. This performs similar functions to a legacy PBX/Key System. The IP PBX is the server that all of the endpoints are logged in to. When a smart endpoint wants to make a call, they tell the IP PBX who they want to call. The IP PBX checks to see if the endpoint is available. If it is logged in and the called party will accept the call, then the call is put through. Many of the features in an IP PBX reside in the endpoint as opposed to a traditional PBX where the features are in the central control unit.

When an IP endpoint requires connection to a phone number on the PSTN a gateway is required. The endpoint tells the IP PBX that it wants to make a call to a specific number. The call is then routed to a gateway device where the number gets dialed into the PSTN and the call progresses as a normal telephone call.

A traditional PBX/Key System that supports IP Telephony and VoIP is referred to as a converged system. This means that the PBX supports traditional telephones, IP endpoints, IP Telephony and VoIP access to another PBX, remote offsite endpoints or all of the above.

Another IP Telephony and VoIP system configuration is an infrastructure based system. This is identical to the above converged system but does not support traditional telephones. All of the control for the infrastructure based system resides on a server in the network and in the IP telephones.

Most business solutions will require connection to the PSTN for the majority of their telephone calls. To connect to the PSTN from your legacy PBX, there is nothing to do since PSTN lines are already connected. To connect to the PSTN from a LAN based IP PBX solution, you must install a gateway. A gateway converts LAN based IP Telephony and VoIP packets to traditional telephone transmission and provide a connection to the PSTN. Asterisk uses internal analog and T1 gateway modules to connect to the PSTN.

The equipment for IP Telephony and VoIP varies depending on the application. The exact list of equipment depends on the specific requirements of your business. IP Telephony and VoIP over the LAN often requires some infrastructure changes and adds traffic to the LAN. Extending IP Telephony and VoIP calls outside of the LAN to remote users over the Internet or WAN links require additional bandwidth planning.

Installing an IP PBX is fairly straight forward. It is actually less complicated than installing a legacy PBX. Since the IP PBX and your IP telephones are located on your LAN, There is no need for additional wiring. The most important issue will be assuring that your LAN is well designed and working as it should.

The major advantage to using an Asterisk IP PBX is that it is an all in one solution. All of the features you need to provide a great business application are included in one comprehensive package. The phone system, voice mail, conference bridge, ACD system and music on hold are all included. This also makes everything much easier to set up, configure and operate. The web based administration features are simple and easy to use.

Advantages of IP Telephony and VoIP

From a purely technical sense, one must consider the way the PSTN handles telephone calls now. Each call is set up and delivered from a pair of dedicated copper wires from the caller to the called party. This creates a dedicated physical connection for a single call with extremely good quality. The technology is sufficient to carry one call at a time over the pair of dedicated copper wires.

VoIP technology packetizes the voice turning it into data packets. These packets are then sent to the network. The same copper wire is now capable of carrying significantly more than one conversation. The same device used to send voice is also capable of sending other packetized information simultaneously like data, video and instant messages. So IP Telephony and VoIP are much more effective at transporting voice, and will produce a much richer experience for the user when one considers the enhanced features of IP Telephony like remote users, enhanced conferences and lower costs.

IP Telephony and VoIP Practicality

Changing over to a new IP PBX system is a major move. This move is going to affect your company for years to come. The average PBX system has a useful life of 7 years. The decision you make now will be with you for a long time. It makes the most sense to make the move to an IP PBX sooner rather than later. Continuing to invest in older proprietary technology will just increase the risk that the system will need replacing before the seven year useful life. Investing in an IP PBX system will provide a platform for the future that will support software updates and enhancements well beyond the useful life of legacy technology.

Over time, legacy PBX's will all be replaced with IP Telephony systems. Be sure to consider the underlying technology. SIP is the standard that the industry has embraced. Keep in mind that open standards SIP based IP telephones are the best investment protection you can have.

Benefits of IP Telephony and VoIP

The primary Benefits of an IP Telephony IP PBX System are:

One Wiring system Instead of separate wiring for telephones and separate wiring for data, all data and voice are on the LAN. There is usually plenty of bandwidth available on a well designed LAN.
Web based administration With an IP Telephony IP PBX, all system administration functions are performed on the network usually through a browser based administration program. This means that the system can be modified from anywhere if required.
Leveraging the Internet for telephone calls When calls flow over the Internet, long distance charges are avoided. This is great for remote workers who can stay logged into the office all the time without incurring any additional charges.
Peer to Peer phone calls All calls are Peer to Peer. This is a big advantage over the traditional PSTN. The call is set up by the IP Telephony server then the call flows between the two endpoints. All of the voice or video traffic is direct between the two endpoints reducing the congestion at the server.
Unified Dialing Plan Everyone who is logged into the system is capable of receiving and originating calls. If an employee is at a remote office in Seattle and a call comes into the corporate headquarters in Chicago, the call can be directed to the employee in Seattle just as if that person were in Chicago. The use of the corporate communication resources such as voice mail, automated attendant and email can be centralized simplifying all support and maintenance.
Remote users All users who are logging into the system are part of the IP PBX. This could be a traveling employee at a hotel with Internet access from a room, a user at lunch with a wireless connection at a cafe or a someone at home logged in for the day while they are under the weather.
Presence Management IP Telephony and VoIP applications can take advantage of presence management. This is a function of the system that allows users to set how other users view their presence on the system. Most systems have tremendous flexibility. Your presence can be set as busy, available, off line etc.
Reduced Costs Cost reduction in operating an IP Telephony system covers just about all areas of the business.
Investment Protection IP Telephony and VoIP and in particular SIP based IP Telephony and VoIP products offer a high degree of investment protection. Since it is apparent that all communications will be IP based within the next 5 years, it makes good sense to begin the shift toward IP Telephony and VoIP as soon as practical. Investing now in an IP Telephony solution that provides interoperability with the new technologies that are available makes a lot of sense.

IP Telephony and VoIP and Security

Opening up your network to the Internet poses some inherent risk. Most LANs have some form of security. This security can put some limitations on IP Telephony and VoIP applications. Most LAN administrators are aware of the vulnerabilities of their network to attack from the outside. IP Telephony and VoIP can operate well in a tight Internet security environment.

Multi-site businesses have most likely established a secure data connection between locations making the introduction of IP Telephony and VoIP an exercise in bandwidth management.

Most successful single site IP Telephony and VoIP deployments only use the Internet to connect remote users to the other users in the system. Use of VPNs for remote users is a secure way of connecting all of the users without exposing the network to extreme risk.

IP Telephony and VoIP Quality of Service

The voice quality of a IP Telephony and VoIP phone call should be at least as good as what the PSTN can provide. This is true as long as enough bandwidth is available for the call. If bandwidth is somehow constrained, quality of service can be affected. In a condition where adequate bandwidth is not available, the call can begin to degrade in quality not unlike a bad cell phone connection.

Quality of service is controlled in several ways. Calls within your LAN environment should not get degraded if the network is well designed.

If you extend your IP Telephony and VoIP calls outside of your LAN over a WAN or out on the Internet, then quality of service does become an issue. Routers and switches are available that can prioritize voice packets to maintain good quality of service. On the Internet, there is really very little that you can control when it comes to bandwidth. In real world experiences, the Internet does seem to be able to provide a good option for IP Telephony and VoIP calls with surprisingly good quality when using broadband connections.

We would be glad to provide you with the assistance required to design your application.

Getting Started with IP Telephony and VoIP

IP Telephony and VoIP systems will provide an advantage to just about any business. There is a lot to know when purchasing a new system. We hope this guide has increased your understanding of how the basic technology may fit into your business application.