Voice over IP (VoIP) has become an important factor in network communications, promising lower operational costs, greater flexibility, and a variety of enhanced applications.

VoIP provides the capability to break up your voice into small pieces (known as samples) and place them in an IP packet.

Signaling System 7 (SS7) is a common-channel signaling standard developed in the late 1970s by the International Telecommunication Union Telecommunication Standardization Sector (ITU-T), formerly known as the Consultative Committee for International Telegraph and Telephone (CCITT).

While VoIP networks have continued to rapidly grow over the past 10 years, the SS7 protocol is important to Voice over IP (VoIP) and the way it interworks with the PSTN. As long as users of VoIP networks need to connect to users of the legacy PSTN, it is critical that the translation points (gateways) between these two networks be fairly seamless and efficient to the carriers. Although all communication might move to VoIP sometime in the future, it is important to provide a smooth migration and preserve some of the usability to which end users and carriers have become accustomed.


Quality of service (QoS) is an often-used and misused term that has a variety of meanings. QoS refers to both Integrated Services (IntServ) and Differentiated Services (DiffServ). Although the two mechanisms greatly differ, the basic goal of IntServ and DiffServ is to achieve the bandwidth and latency needed for a particular application.

Voice over IP (VoIP) comes with its own set of problems. QoS can help solve some of these problems namely, packet loss, jitter, and handling delay.

Some of the problems QoS cannot solve are propagation delay (no solution to the speed-of-light problem exists as of the printing of this book), codec delay, sampling delay, and digitization delay.

Indeed, building a network to run VoIP is complex. Proper QoS is a critical step in ensuring good voice quality.

Billing and mediation services are important in voice over IP (VoIP). They are key factors in helping a service provider or an enterprise vendor understand financial aspects, such as Return on Investment (ROI), when migrating its time-division multiplexing (TDM)-based network to VoIP.

Security is an important consideration in designing and implementing VoIP service. By its very nature, it encompasses almost every aspect of a network from Layer 2 devices to firewalls and Certificate Authorities.

A wide range of security technologies exist. Assessing the security risks and deploying technology that is appropriate for those risks is imperative to protecting VoIP services.

Enterprise Voice over IP (VoIP) applications include business voice services and features, site-to-site voice calls over IP networks, Public Switched Telephone network (PSTN) access, unified messaging, and advanced IP services such as instant messaging and presence-enabled networks.

VoIP has already drastically changed the way we communicate with each other on a daily basis. Right now, it is highly likely that you have already talked to someone over an IP network.