y moves to embrace standards," PC Week November 18, 1996 v13 n46 p. N16. McLean, Michelle Rae. "RSVP: promises and problems," LAN Times October 14, 1996 v13 n23 p. 39-42. Plain, Steve. "Streamlining," Computer Shopper December 1996 v16 n12 P 620. Rogers, Amy. "A blueprint for quality of service," CommunicationsWeek November 18, 1996 n638 p. 1. Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, RFC 1889, "RTP: A Transport Protocol for Real-Time Applications," IETF, January 1996. Schulzrinne, Henning and Casner, Stephen, "RTP: A Transport Protocol for Real- Time Applications," Audio-Video Transport Working Group, Internet Engineering Task Force, working draft, October 20, 1993. Steinke, Steve. "The Internet as your WAN," LAN Magazine October 1996 v11 n11 pp. 47-52. Tannenbaum, Todd. "IP Multicasting: Diving Through The Layers," Network Computing November 15, 1996 pp. 156-160. CIRCUIT-SWITCHED NETWORKS "It's kind offun to do the impossible. " Walt Disney (1901-1966) WO types of networks can be used to transport video/data conferencing signals, circuit-switched and packet-switched. In this chapter, we will discuss circuit-switched networks; in the next, we will discuss packet switching. Until Ethernet really became established, in 1979, the concept of packet switching was scarcely implemented anywhere. Today, packets traverse LANs and WANs all over the world; indeed, many people use the word networking to refer to packet-switched service exclusively, without acknowledging that circuit switching, a different type of networking, is older by almost a century. Today, the bulk of video conferencing takes place over circuit-switched telephone lines, such as ISDN or Switched 56, or over dedicated lines, such as T-1 or fractional T-1. Even when the conference endpoints are workstations on the same LAN, they typically use telephone lines, not the LAN, for video conferencing traffic. For that reason, we will start our discussion of video/data conferencing networks with a look at the public switched telephone network 