Industrial Ethernet

GlossaryTechnical appendixTwisted-Pair CableA twisted-pair cable is a symmetrical copper cable consisting oftwo wires that are twisted together. The conductors consist ofinsulated copper conductors. In contrast to asymmetricalcables, such as coaxial cables, symmetrical cables do not havereference potential. The advantage is that wires can be arrangedto prevent interference between the lines.Virtual Mapping (NAT)NAT stands for „Network Address Translation“. The NATprocess is used to enable computer in a private network tohave shared access to the Internet. In NAT, IP addresses froma private network are registered and then assigned to publicIP addresses. The advantage of the NAT process is that allcomputers can communicate within their company-wideIntranet, but require only one IP address for access to theInternet. Internal network addresses are kept hidden from thenetwork and are not publicly visible. When a computer initiates aconnection to an external computer, a pointer is assigned to it inthe NAT routing table.VLANVirtual networks or virtual LANs (VLAN) are a technologicalconcept for implementing logical work groups within a network.This type of network is implemented using LAN-switching orvirtual routing on the link layer or on the network layer.WebserverA web server is a server programme that provides files via HTTPprotocol. These files are usually websites, pictures and stylesheets. It makes no difference to the webserver what type offiles it supplies. Each time a web site is requested (for exampleby clicking a link), the browser sends an HTTP query to a webserver. This web server can then send the site requested back.The standard ports for the web server are 84 HTTP protocol and443 for HTTPS, the encrypted HTTP (for example with SSL).Usually all page requests are saved in a log file, from where - byusing log file analysis - different statistics on access can begenerated. However these do not give the full picture, as HTTPis a connectionless protocol.WW.15