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

Computer Networks and Securitylogical Internet addresses. The role of this administrative layer is similarto that of the telephone operator. The operator provides connections,distributes telephone numbers and verifies wrong numbers, retries theconnection after a busy signal, switches connections onto other networkswhen the main network fails, troubleshoots the mechanical connectionand informs the calling party of network problems.While hardware problems are more easily diagnosed, networksoftware problems can be narrowed to specific nodes with software toolsand protocol analyzers.Network software can provide functions such as system boot, networkinitialization and systems monitoring. Simple networks buildupon TCP/IP protocols which are the predominant Ethernet software.These provide intercommunication between nodes for messages, fileexchange and terminal services. This can include remote workstationoperation, remote boot, and remote device access and services.Internet ProtocolThe Internet protocol had its roots in a communications addressingscheme known as the Address Resolution Protocol (ARP). This formedthe basis of the Department of Defense’s Advanced Research Project(DARPA) four-node network called Arpanet.Arpanet evolved into the Internet during the 1970s as TCP/IP wasadapted for LANs using Ethernet. The IP address contains a networkand host address divided into parts.The Internet protocol provides the lowest level of software accessand interface to the Ethernet environment. This protocol provides linkinitialization and termination, node recognition, and packet control operations.Transmission Control Protocol is a higher level communicationprotocol. This protocol sequences data transfers and the actual packettransmissions. TCP resides at the OSI layer 4, while IP is OSI layer 3.Internet-enabled NetworksThis type of network makes it possible to manage, view, and controlprocesses, network devices, and configurations from applicationsand standard Web browsers. Implementing a Web network allows visu-©2001 by The Fairmont Press, Inc. All rights reserved.