local area network as a separate network. This network would then be a part of the larger WAN. The hub passes all data from its input to all of the lines on the network. This is one of the reasons for creating smaller networks or sub-networks—to isolate data transmission between computers.
Alternate broadband connection
An alternate way to connect a simple network is to use a computer with two network interface cards as shown in Figure 2-4. In essence, this computer (and appropriate soft- ware) acts as the gateway and router for your local area network. It is important to note that one NIC has a network address that is known only to the WAN or Internet and the other NIC has a network address that is known only to the LAN. These addresses can be either static or dynamically allocated. This would allow you to use static IP addresses on your LAN and connect to your ISP with static or dynamic addresses. Windows 98 Second Edition directly supports multiple NICs and Internet sharing, and there are numerous software packages that can add this function to either Windows or Linux.
Dial up connection
A final alternative for connecting your LAN to a WAN or Internet is the use of a PPP connection through a dial-up modem. This is shown in Figure 2-5. Point-to-Point Protocol (PPP) is a protocol for communication between two computers using a serial interface, typically a personal computer connected by phone line to a service provider. But this can be as simple as a serial line with no modem. Essentially, it packages your computer’s TCP/IP packets and forwards them to the server.
Figure 2-5: PPP network connection
The 10/100 Base-T cable
Ethernet uses a special type of cable called twisted pair. Twisted pair cable is made of four pairs (in this case) of insulated copper wires that are twisted around each other in pairs to reduce electromagnetic induction between pairs of wires. The combination of these four sets of twisted wires forms a network cable that is com- monly referred to as Category-5 or CAT 5 cable. It derives that name from the American National Standards Institute/Electronic Industries Association (ANSI/EIA) Standard 568, in which this cable is specified. That same specification lists several standards that specify categories of twisted pair cabling systems (wires and connec- tors) in terms of the maximum data rates that they can reliably sustain. This specification describes the cable material as well as the types of connectors and junction blocks to be used in order to conform to a particular category. CAT5 cable is different from the wire you buy at your local hardware store for connecting your phone or computer modems to a wall jack, which is not twisted pair, but is a side-by- side wire also known as silver satin.
The two most popular specifications are CAT 3 and CAT 5. While the two cables may look identical, CAT 3 is intended for a lower data rate and can cause transmission errors if used for faster speeds. CAT 3 cabling is for signals that are 16 MHz or less and is suitable for 10base-T networks, while CAT 5 cable must pass a 100-MHz test to be suitable for 100base-T networks.
The connector on a 10/100 BASE-T cable is an RJ45, which is short for Registered Jack-45. This is an eight-pin connector that is commonly used for network cables, especially Ethernet. The RJ-45 connectors look very much like the modular connectors