با سلام بنده دارم کتاب نتورک پلاس رو می خونم میشه لطف کنید و این قسمت رو یکمی برام توضیح بدید و اینکه تکنولوژی جدید تری هم اگر هست برام بگید
Connecting Hubs
You can build a simple Ethernet LAN by plugging a number of computers into a single hub, but what happens when your network outgrows your hub? The solution is to get another hub and connect it to the first one. Large networks can have many interconnected hubs forming large LANs, which are in turn connected by routers. Almost every Ethernet hub on the market has an extra port called anuplink port, which is used to connect to another hub instead of to a computer. The uplink port is wired differently from the other ports in the hub.
As explained in Lesson 1, UTP cables contain eight wires in four pairs, and each pair consists of a signal wire and a ground. Computers transmit data over one wire pair and receive data over another. In most cases, the other two pairs of wires are left unused. For two computers to communicate, the transmit contacts on each system must be connected to the receive contacts on the other system. In all but exceptional cases, UTP cables are wired straight through, meaning that each of the eight pins in the connector at one end of the cable is wired to the corresponding pin in the connector at the other end. If you were to use a cable like this to connect two computers, you would have the transmit pins connected tothe transmit pins and the receive pins to the receive pins, making communication impossible.
Another function of a hub is to provide the crossover circuit that connects the transmit pins to the receive pins for each connection between two computers. The uplink port is the one port in the hub that does not have the crossover circuit. When you connect the uplink port in one hub to a regular port in another, you enable the computers on one hub to connect to those on the other, with only a single crossover between them. Without the uplink port, connecting one hub to another would cause a connection between computers on different hubs to go through two crossover circuits, canceling each other out. To avoid such a connection failure, you shouldn't plug an uplink port on one hub into the uplink port on another.
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