Network structures and network configuration2.2 Network structuresIndustrial Ethernet76 System Manual, 09/2019, C79000-G8976-C242-10A further restriction for networks with line structure exists in the physical arrangement of thenodes. Depending on their position, the backbone may need take long detours which may, inturn, lead to problems with frame delay times. In the case of linear network topologies,network components such as switches typically have only one or a few connection points fornetwork nodes. Linear bus structures can also be created with devices with two integratednetwork interfaces.SetupThe line structure can be realized through SCALANCE X switches. Any TP ports can beused to cascade and form a linear bus. The number of SCALANCE X switches that may becascaded depends on the response times of the applications that are to be operated via thisline.● Electrical cablesThere may be a maximum distance of 100 m between two of these devices.● Optical cablesAt 100 Mbps, the maximum distance between 2 devices can be as follows:– Multimode, glass, up to max. 5 m– LD: Single mode, glass, up to max. 26 km– LH+: Single mode, glass, up to +max. 70 kmAt 1 Gbps, the maximum distance between 2 devices can be as follows:– Multimode, glass, up to max. 750 m– LD: Single mode, glass, up to max. 10 km– LH: Single mode, glass, up to +max. 40 km– LH+: Single mode, glass, up to +max. 70 km– ELH: Single mode, glass, up to max. 120 km2.2.3 Star structure"Star"The difference between the star topology and linear bus topology is that one switch functionsas the central node from which the spokes branch off to the individual nodes. The individualnodes of the network therefore have separate point-to-point links with the active networkcomponent (i.e. with the switch).The immediate effect is that the messages only run via the spokes between sender andrecipient, in other words network performance improves significantly because several nodescan communicate at the same time.Depending on the requirements, in practice this may be a mixture of fiber-optic cables andtwisted pair cables on the individual transmission links. Typical applications are Ethernetoffice networking or the networking of production cells in manufacturing with IndustrialEthernet.
