VoIP devices, protocols, and codecs combine their roles to form the complete service you experience whenever you make an Internet phone call (Figure 1.8). Figure 1.8. A typical Internet phone scenario
As you can see, you do not actually connect your phone to any telephone company's system. There is no requirement for you to remain in one place; in fact, you can be literally anyplace on Earth that has Internet connectivity and make a call as though you were right in your armchair at home. The called party will hear no difference (Internet connection quality being the same), and you will continue to receive calls on your home number even while you're on vacation in Paris! Imagine traveling with your local phone and being able to check in with friends and neighbors without the high-priced hotel phones or calling cards you typically use on a trip. Follow an Internet phone call step by step as it is initiated by a VoIP caller (Figure 1.9): Figure 1.9. A VoIP call step by step
Internet telephony resourcesAre you the type of person who needs to know more about your phone than just how to hook it up? Do you lose sleep wondering what makes it work or whether your conversations are truly confidential? This section explores some VoIP resources you can use to learn more about VoIP technology, codecs, protocols, and standards. I'll list a few Web sites (mine included) where you can learn more. If you could care less? Well, I'll see you in Chapter 2 in just a minute. More about VoIP standardsVoIP standards are ratified by the International Telecommunication Union (ITU-T) and the Internet Engineering Task Force (IETF). Indeed, most of the codecs used in VoIP were created for use in traditional telephone systems. The SIP session protocol was ratified by the IETF and has been integrated with the ITU-T standards to allow interoperability. You can learn more about the standards behind VoIP at my Web site (www.firethephoneco.com), the Web site of the ITU-T (www.itu.int/itu-t), or that of the IETF (www.ietf.org). Especially interesting for those who need good bedtime reading is the IETF's SIP Request for Comments document, RFC 3261 (www.ietf.org/rfc/rfc3261.txt). You can find a good discussion of VoIP codecs at the VoIP Wiki: www.voip-info.org/wiki-Codecs Keep on readingChances are that if your question hasn't been answered yet, it will be in the next several chapters, which discuss the evaluation, installation, and optimization of your Internet phone service. You'll use everything discussed in this chapter and more as you go through this process. Let's rejoin the group now, shall we?
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