IP Telephony

This is what this book is about: voice over IP. The IP-based network could be the public Internet, or it could be some kind of “managed” IP-based network service. A managed IP service is typically one in which the service provider not only gives the customer links to the global Internet, but also has circuits (virtual or real) that have the link’s bandwidth dedicated exclusively for the use of that particular customer. The IP network could even be a local area network (LAN) within an organization’s sole site or office campus complex. No matter: It is the presence of IP that counts. Voice over IP is still VoIP whether the IP runs on a LAN, across LANs linked by point-to-point private lines, a managed Internet service, or the global public Internet. There are important differences in the voice quality of service (QoS) that may be expected, the savings involved, and the equipment needed, but all these considerations will be discussed here as well.