Network Layout Guidelines
Length of Network Links - Each network link (from hub to terminal) can be a maximum of 100 m (325 ft.) in length.
Number of Hubs - There can be only two wire segments and one hub between any two terminals (2/1 rule). A wire segment includes all of the circuit elements that provide the physical electrical connection between workstations and hubs. For example, a wire segment can include drop cables, wall boxes, in-store wiring, jack panels, and patch cords. Therefore, the diameter of the entire network is limited to 200 m (650 ft.). Hubs cannot be nested to gain ports as can be done in 10Base T networks, i.e. links from hub to hub. To accommodate for this restriction, many 100Bast-T Ethernet hubs have large numbers of ports.
Stackable Hubs – Stackable hubs permit starting with 8 or 12 100Base T ports and then expanding to as many as 80 or more ports. This method does not violate the one-hub rule.
Large Networks – 100Base-T network configurations of more than 40 terminals is not certified by NCR. Before configuring a large network you should test the application to validate that there is sufficient bandwidth available in the network and servers. Remember to consider future needs. It may be necessary to locate multimedia-intensive terminals (i.e. video promotions) on a separate network from networks that demand fast response times (i.e. POS terminals).
Mixing 10 Mb/100 Mb Terminals - It is not possible to mix terminals that are running 10Base T (10 Mb/s) and those running 100Base T (100 Mb/x) on the same hub. Certain Ethernet switches permit a mix of speeds (see below), however these switches are very expensive. Evaluate the cost of upgrading any existing 10 Mb/s terminals to 100 Mb/s before deciding to purchase a dual speed switch.
Dual Speed Switches – Switches operate differently than do hubs. Hubs repeat all network traffic to all terminals on the network. Switches direct the traffic to specific terminals. All terminals on the network can receive/transmit simultaneously, without collisions. Thus the full 100Mb/s bandwidth is available to all ports.
The full benefit of switches is realized only if the network servers can handle the load. Switches with a 1 Gb/s server port, or support for both 10 Mb/s and 100 Mb/s terminals, are expensive but do offer superior performance to hubs in many applications. Hubs can be installed initially and then upgraded to switches.
Mixing 100Base T Network Variations – Terminals must be connected to a IEEE 802.3u 100Base TX hub or switch. Other network variations, such as 100Base VG and 100Base T4, do not operate with 100Base TX.
Connecting Twisted Pairs - When connecting twisted pairs to wall boxes or patch panels, each pair may be untwisted a maximum of one inch.