The Network Interface Card or NIC is the hardware heart of network communications. Like anything else they are available at various quality levels and there will always be those who think a cheap one is as good as any other - don't believe it. I highly recommend that you choose a quality, PCI based (for those with PCI slots), Fast Ethernet card. I currently use the Intel Pro 100+ for both home and business installations and find it to be a most excellent product. A few other good brands you will commonly run across are DEC, SMC, Adaptec and 3COM.
A fast Ethernet (100baseTX) NIC is today priced very close to the standard Ethernet (10baseT) NIC and I believe choosing the standard 10MB/s NIC over the enhanced 100MB/s product to be penny-wise and pound foolish. The fast Ethernet NIC's are backward compatible and will run at 10MB/s for communication with existing 10baseT network devices.
A cheap NIC can be problematic in installation, performance and reliability. Their drivers are generally not kept up-to-date and even if they seem to be operating OK, there is usually a performance penalty in terms of CPU usage, caveat emptor.
UTP or Unshielded Twisted Pair is the cable of choice today. With coax cabling (10base2) you will avoid needing a hub for more than two systems but you will be locked out of fast Ethernet speeds, full duplex capabilities, and also create a more difficult troubleshooting environment. UTP is thin, flexible and less expensive than coax.
The UTP cabling, and connectors must be category 5 (CAT 5) rated in order to be reliable at fast Ethernet speeds. Their is little reason to wire with lower quality cable, even if initially using 10baseT speeds. CAT 5 UTP cable has eight wires bundled as four pairs. Each pair is twisted together providing a partial clue to the naming of the cable. You will notice when examining the cable that the wires are color coded and that the twisted pairs are combinations of a solid color and the same color alternating with white. The most typical pair implementation is that of white-orange/orange, white-green/green, white-blue/blue and white-brown/brown. 10baseT and 100baseTX both use RJ45 connectors, an 8 pin connector very similar to that which your telephone uses. Even though only two of the four pairs of wires are actually used, proper wiring standards should be followed for obvious reasons. The current in favor wiring practice is labeled T568B. The pin assignments for T568B are:
Notice that, among others, pins 1 & 2 and pins 3 & 6 are crimped to actual twisted pairs (the white-green wire is twisted around the green wire). These are the pins used by the NIC's: a receive (RX) pair and a send or transmit (TX) pair, and if nothing else this relationship (pins 1 & 2 being an actual twisted pair and pins 3 & 6 being an actual twisted pair) must exist or the cable will not perform properly, if at all; continuity is not enough. I wanted to touch on this as it is probably the single most common error made by both the do-it-yourselfer and some so-called for hire "cable installers". I have even seen ready made cables improperly wired!
Crossover cabling is covered in the Hub section. This is just a primer and there are many treatises on the net regarding cabling and I leave it to the reader to locate more exhaustive information as desired.
The NIC's are normally connected to a hub whose basic function is to broadcast the information each NIC puts on its transmit pair to the receive pair of all the other ports ensuring that all NIC's connected to the hub will see all of the information, A standard 10baseT hub for home networks is relatively inexpensive. One can expect to pay a premium for fast Ethernet capability as well as extras such as manageability and stack-ability that may be needed in a business environ but rarely at home. It does, as always, make sense to invest in a known quality product from a major vendor.
A switching hub is important in environs that demand the highest possible throughput. Unlike a standard hub which shares the bandwidth among all connected devices the switch provides full bandwidth to each device and also allows for full duplex operation as each connection is true point-to-point and non-broadcast in nature. Switches are currently a magnitude leap in expense over a standard hub.
For a small two system 10baseT network one can dispense with the hub (you can always add it later when your network grows) and use a crossover cable which is to network cabling as a null-modem cable is to serial cabling. Basically the cable itself is wired to do the job of the hub, that is the transmit pair and the receive pair are crossed at one end so that when NIC A puts some information on the TX pair it is seen by NIC B on the RX pair and vice-versa. Wire one end of the cable T568B and the other end T568A, which switches the white-orange/orange pair with the white-green/green pair and you have a proper crossover cable.
Last modified: January 16, 2002