 page intentionally left blank I Section Inree Section Inree Section Inree Section Inree Section Three Network communications This page intentionally left blank Chapter 3.1 Data and voice traffic Juanita Ellis, Charles Pursell and Joy Rahman In the past, voice and data networks had been kept core architecture of converged network, we must separate. Legacy network technologies simply could not understand the behavior of voice and data traffic and meet the diverse performance requirements of both how networks perform on different network traffic. voice and data. Advances in networking technology, including fast Ethernet, wire-speed switching, and Policy-Based Quality of Service (QoS) management, have made it possible to build converged voice and data Packet switching versus circuit networks. Converged networks enable a new generation switching of integrated voice/data applications. For example, with converged networks, users of web-based e-commerce There are primarily two types of networks, circuit applications can view product information while talking switched and packet switched (Table 3.1-1). A good ex- with customer service agents in a call center, through ample of circuit switching is the telephone system. Cir- a single network connection. The focus of most cuit switching is a technique in which a system seeks out converged network strategies is Voice over IP (VoIP). the physical "copper" path from the caller's telephone to VoIP refers to the transmission of telephone conversa- the receiver's telephone. There is a need to set up an end- tions over a packet-switched IP network. This IP net- to-end path before any data can be sent. This is why it can work could be as small as a single subnet, private LAN, or take several seconds between the end of dialing and the as large as the public Internet. With VoIP on the LAN, start of ringing for international calls. During this interval, telephone conversations are converted to a stream of IP the telephone system is actually hunting for a copper path, packets and sent 