HVAC Control in the New Millennium.pdf - HVAC.Amickracing

Building Automation, Wireless Technology and the InternetTCP/IP is a packet-switching networking scheme. Information issent across the network in a packet that contains source and destinationinformation. Since each packet has its addressing information built in, itcan travel independently. This allows large numbers of packets to flowthrough the network taking different routes. Packets may arrive out oforder, but because each packet also contains sequence information, thereceiving computer can reconstruct the original data.The high-speed central networks in the Internet are known asbackbones. They are like a superhighway system and they deliver datato mid-level networks. The mid-level networks take the traffic from thebackbones and distribute it to regional networks which are more likelocal highways in the automobile world.Client/Server SystemsAny two computers connected on the Internet act like they are ina client/server mode. A client is a computer connected to a host computer,which is called a server. The client software is used to run programsacross the network. The client program provides the user interfacefor working with the server. It takes commands you execute fromyour computer and transfers them to the server program running on thehost computer. For example, a client program called browsers allowsyou to connect and work with a World Wide Web server.Although the Internet uses the telephone system, it is not a networkprimarily based on dedicated telephone lines. The telephone networkis a circuit-switched network. When you make a call, you get aswitched or dedicated connection. Even if you are not talking or listening,this connection is unavailable to others who may want to use it.This means there is some under utilization of this resource. The Internetworks more like a mail service where mail is mixed together and sent ina bag or packet to another location and sorted out for its destination.RoutersThe Internet uses computers called routers to connect the variousnetworks together. These can be LANs (Local Area Networks), regionalnetworks and even telephone lines. Information on the Internet movesthrough the telephone lines and the other nets. The routers make decisionson how to route the data packets so they reach their destination.©2001 by The Fairmont Press, Inc. All rights reserved.