over an Ethernet network. This network and the call request signal must propagate all the way to is usually restricted to a building or campus. As VoIP the destination and be acknowledged. No one else can use technology matures, new conversion methods may the physical path at the same time. emerge. Regardless of the method that is used to On the other hand, packet switching is a type of convert VoIP traffic for LANs, VoIP traffic will always network where small units of data are routed through traverse the LAN as a stream of IP packets. One of the a network based on the destination address in each packet. key challenges in implementing VoIP is to design and Compared to circuit switching, which statically reserves build an IP-based network that meets QoS re- the required bandwidth in advance, packet switching quirements and is comparable in performance to con- acquires and releases bandwidth as and when it is ventional circuit-switched telephone networks. The needed. This type of communication between sender and high latency forwarding and best-effort delivery pro- receiver is known as connectionless. Circuit switching is vided by traditional software-based routers is generally completely transparent. The sender and receiver can use not acceptable for streaming traffic such as VoIP be- any bit rate, format, or framing method they desire. As for cause it does not provide maximum latency guarantees packet switching, the carrier needs to determine these or minimum bandwidth guarantees. To understand the basic parameters first before transmission can occur. Communications Engineering Desk Reference; ISBN: 9780123746481 Copyright © 2003 Elsevier Inc. All rights reserved CHAPTER 3.1 Data and voice traffic The Internet is based largely on packet switching, and transmission path from end to end. Video is a hybrid of the Net is basically a huge connectionless network joined both. together. By transmitting data in packets, the same data Most computer networks currently use "packet path can be shared among many users in the 