IP Telephony 201: The Nuts and Bolts of VoIP

  • Written By: David Clark
  • Published On: May 2008



In IP Telephony 101, I looked at the pros and cons of IP telephony, and a few of the considerations you should explore before making the switch to VoIP.

We’ll turn now to the nitty-gritty of VoIP systems: the architecture, the equipment, the network structure, the software, and what you can expect to pay.

But before we start, let’s get WAN and LAN out of the way. A LAN (local area network) serves a small geographic area (such as a localized group of buildings). A WAN (wide area network) is suitable for broad geographic areas.

Architecture
VoIP architecture refers to the sum total of your VoIP system components, including hardware (computers, phone systems, routers, switches, hubs, cables and so on) and software (whether for telephony, audio conferencing, video conferencing, Web conferencing, contact center, or mobile solutions).

Equipment
Router: A router is a kind of cross between a control freak and a traffic cop: it tells data where to go, and how to get there. Sitting between subnets* or individual computers, the router also helps determine communication speed (so do communication lines—more on that in a bit). A router uses a “one-to-many” approach, which means that information from a single source is sent to a network of computers, where it is collected by the recipient computer.

* A subnet is a network or grouping of computers, whether linked geographically or via a LAN or WAN.

Switch: A switch controls the direction and destination of data within a subnet.

Hub: A hub is much like a switch. The distinction is that whereas switches direct data from Point A to Point B, hubs direct data to all ports, and Point B is expected to recognize that the data “belongs” to it, as the data becomes available.

Communication Lines:
The kind of lines or cables you use determine the rate at which data is transmitted (uploaded and downloaded). Common line types: T1 (capable of transmitting 1.5 million bits per second), T3 (45 million bits per second), and DSL (between 128 Kbps to 6 Mbps for sending data [“downstream”], and between 128 Kbps to 512 Kbps for receiving data [“upstream”]).

Your choice of equipment will affect the speed at which you can transmit voice data, as well as the number of users your VoIP system can support.

Network Structure
Your network structure (AKA topology or layout) determines the way in which all computers in a network are connected. Network structure types include point-to-point, bus, star, ring, mesh, tree, star-bus, star-of-stars… These rather esoteric terms, not surprisingly, refer to the “shape” of the network. A “ring” network, for example, consists of a structure where computers are distributed in a ring formation, with each computer connected to two others.

Some network structures offer better redundancy than others. If a network is cursed with low redundancy, a connection failure from or to one computer can have a dramatic effect on all the computers on the network.

Full redundancy, while the most reliable option, is also the most expensive, since full redundancy requires more routers, more wires, and (potentially) more software.

VoIP Software
Different VoIP software applications offer different capabilities. Call routing, messaging features, remote administration, e-mail integration, video, conferencing… Be sure to conduct a thorough evaluation of your business processes and requirements before succumbing to the allure of bells and whistles you may not need.

How Much?
Well, you get what you pay for… the price can range from under 100 dollars to connect a few computers in a home office, to tens of thousands of dollars for an enterprise organization with thousands of users. For medium-sized businesses with hundreds (and not thousands) of users, you’re looking at a few thousand dollars.

Problem areas for VoIP are and have always been reliability (including issues related to downtime), quality, and possibly scalability, depending on your business model. These issues relate directly to network structure and your telephony equipment. Looking for more reliable equipment and structure? It’ll cost you more.

So how do you save money? By making the right decision the first time: by choosing a system which meets the requirements of your organization, now and in the future. I recommend you read the white papers below to help you in your research. And don’t hesitate to contact me by leaving a comment below.

1. 7 Steps to a Successful IP Telephony Implementation
2. What You Need to Know about VoIP
3. Voice over IP Reliability
4. How to Buy a Phone System
5. The Definitive Guide to Successful Deployment of VoIP and IP Telephony—Chapter 1
6. The Definitive Guide to Successful Deployment of VoIP and IP Telephony—Chapter 2
7. Voice over IP Manageability
8. Hacking Your PBX: 15 Ways to Make the Most of a Modern Phone System
9. Internet-based Phone Service for Small to Midsize Companies
10. The Return on Investment of IP Telephony Management

Thanks to TEC analyst Jeff Spitzer for his expertise.
 
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