CHAPTER 2: Network Media 76 provides such a connection between a cable and a device. Because the media used on a network can differ, a number of different connectors have been developed over the years. Twisted-Pair and Coaxial Cable Connectors Several types of connectors are available for coaxial cable. Depending on the need, connectors that connect to different cable and devices are available for twisted-pair and coaxial. These include: D connectors RJ connectors DIX connectors BNC connectors F-Type connectors D Connectors The D connector gets its name from its shape. As shown in Figure 2.2, with some imagination, the D connector can be seen as looking like a letter D turned on its side. A male connector is one that has pins protruding from it, while a female connector has holes into which the pins fit. The number of pins used in a D connector varies, but always correspond to the number used in the D connector’s name. These include: DB9, which has nine pins. DB15, which has 15 pins, and we’ll discuss further in this chapter  when we examine DIX connectors. DB25, which has 25 pins. RJ Connectors RJ connectors are used with twisted-pair cabling and can be used to provide connectivity to a cable used by telephone and data devices. Because they are used for different purposes, there are several different variations of RJ con- nectors available. rJ-11 RJ-11 connectors are used on twisted- pair cables that are used by tele- phones. You can easily find an RJ-11 connector in your home by looking at the ends of the cable running from FIGURE 2.2 DB15 Connector. Connectors 77 your phone into the wall jack. They are also used to plug dial-up modems into the phone line so that computers can dial into the Internet or access networks remotely using the phone line. They are primarily used in North America and are not widely used in other countries throughout the world. RJ-11 connectors have four pins to support four of the wires in a twisted- pair cable. Although the connector can be used with different categories of twisted-pair, only two pairs of wires are used, even if the cable contains more than four wires. rJ-45 The RJ-45 connector is used with twisted-pair cables that support data com- munication. As such, they can be used with Categories 3 and higher of UTP or STP cabling. They are commonly seen on today’s networks, as they are used on both Ethernet and Token Ring networks. An RJ-45 connector looks like a RJ-11 connector, but wider. RJ-45 con- nectors are similar to the phone connectors except that instead of four wires found in the home system, the network RJ-45 contains eight contacts. There are eight pins in the connector; hence eight wires in the cable are connected to it. Ethernet can use four of the wires or possibly all eight, depending on the media standard being used. As we saw earlier in this chapter, a special crimp- ing tool is needed to make contact between the pins and the cable inside. rJ-48 and rJ-25 In addition to the RJ-11 and RJ-45 connectors that are used for voice and data communication, there are also a number of other RJ connectors that may be found in offices. The different types are used to provide different services, but are all used with twisted-pair cabling. RJ-48 connectors are essentially the same as the RJ-45 connector, but used with STP cable. Like the RJ-45 connector, it uses eight pins to provide contact with the eight wires in a twisted-pair cable, although a different pin arrangement is used in connecting the wires. Another example of a RJ is the RJ-25 connector. RJ-25 connectors use six conductors to allow multiple phone lines to be used. They are often seen when telephones have three line connections. DIX Earlier in this chapter we discussed D connectors and how they consist of pins that are inserted into a female connector. One type of D connector is a DIX, which is used with an AUI that’s used with 10Base5 cable. A DIX connector looks similar to the connector used for attaching a joystick to a joystick port. DIX connectors can be found on the back of some network cards and allow the card to be used with different types of media. ChApTEr 2: Network Media 78 BNC The meaning of the acronym BNC is something that is a topic of debate. It is commonly referred to as a British Naval Connector, but it is also referenced as meaning Bayonet Neill Concelman or Bayonet Nut Connector. Regardless of your preference, the BNC connector is used with coaxial cable. If you’ve ever looked at the end of the cable used for your cable televi- sion, you’ve seen one that looks similar to what’s illustrated in Figure 2.3. The copper wire running down the center of the cable protrudes from the center of a BNC barrel connector. The connector is threaded, allowing it to be screwed onto devices with a corresponding connector, so that the wire can fit into the female connection. There are different variations of the BNC connector that can be used on a network. BNC connectors are used to connect 10Base2 coaxial cable to a hub, while a T-connector (Figure 2.4) can connect a workstation’s cable segment to the network backbone. A special crimping tool is used to put the connector on the end of the wire. The actual wire runs down the middle and must make contact with the end of the connector shown in the middle. EXERCISE 2.2 Terminating a Coaxial Cable Now that you have learned about coaxial cable and how to identify it, we will learn how to terminate a coaxial connector on to a RG type cable. As with twisted-pair cable termination, you will need to use crimping 1. and stripping tools when terminating a coaxial cable, although the process itself is a little different. For one, you will need a stronger cutter that is sized properly for the job of cutting thick coaxial cable. FIGurE 2.3 BNC Barrel Connector. FIGurE 2.4 BNC T-Connector. Connectors 79 To terminate the cable, you will need a ratchet crimper, a pair of 2. coaxial cable strippers, the coaxial cable itself, and BNC connectors. Use the cable cutter to cut a length of coaxial cable from a bulk spool 3. if you have one available. The cable should be the proper length for the job, plus some extra slack for you to make some mistakes when cutting your cable. Remember, never cut cable (especially preexisting runs) without giving yourself a little extra cable to play with. Next, use the cable stripper to remove the excess jacketing and 4. outside coating of the cable. Apply the RG-type connector on the cable and crimp it down.5. Do both sides of the cable if not already done.6. Make sure you test the cable and ensure that it is within specifications.7. RG and F-Type Connectors F-type connectors are used to terminate coaxial cable and are commonly seen on RG-58 (Thinnet) and RG-59 (Thicknet) coaxial. Although it is an older type of connector, it is still frequently used. These connectors have the ability to screw onto televisions, VCRs, and devices for cable television, and are low in cost. Fiber Connectors There are a number of different connectors that are used with fiber-optic cable. As is the case with some of the connectors available for twisted-pair and coaxial cable, some of these are used with older technology and are not routinely seen on modern networks. They include: Straight tip Standard connector Local connector Mechanical transfer registered jack Standard Connectors SC stands for standard connector, and is a suitable name, as it’s the most com- mon type of connector used with fiber-optic cable. It is often used with Cisco equipment. As shown in Figure 2.5, the SC terminates the fiber-optic cable by attaching to its end, using a locking mechanism that clicks into place. CHAPTER 2: Network Media 80 ST Connectors ST connectors are an older version of connector used on fiber-optic cable. It is often seen on older 10BaseFL networks. The ST connector has a screw-on type of locking mechanism that attaches to the tip of a fiber-optic cable and terminates it. In using this type of connector (shown in Figure 2.6), you will find that it has the look and feel of a BNC connector, making it easy to use. Local Connectors The LC is another common connector used on fiber-optic networks. LC is a high-performance connector that is used on many networks. LC connectors use a locking mechanism that’s similar to the SC, which click into place. The connector is seated into place by pushing it in and snapping it into place. FIGURE 2.5 SC Connector. FIGURE 2.6 ST Connector. Exam Warning An easy way to remember the SC is by thinking of its name (standard connector), which indicates that it’s the most common one used today. An alternative method of remember- ing it is to think of SC as stick and click. This will help you to remember that it uses a click-into-place locking mechanism. Exam Warning An easy way to remember the characteristics of an ST connector is by using its nickname stick and twist. This will help you to remember that it is a screw-on type of connector, as you stick and twist it on. Exam Warning An easy way to remember the characteristics of an LC connector is by thinking of the term lock and click. This will help you to remember that its locking mechanism requires you to push and click it into place. 81Recognizing Category 3, 5, 5e, and 6 UTP Mechanical Transfer Registered Jacks The MTRJ is similar to the LC con- nector in that it is a duplex con- nector. As shown in Figure 2.7, it uses a form factor and latch that is similar to the RJ-45 connectors dis- cussed earlier in this chapter. It is also easier to terminate and install than some of the other types of fiber-optic connectors we’ve discussed, such as the ST and SC connectors. RECOGNIZING CATEGORY 3, 5, 5E, AND 6 UTP, STP, COAXIAL CABLE, SMF OPTICS CABLE, MMF OPTIC CABLE, AND OPTIC CABLE Although we’ve already provided you with a lot of information about cabling and their respective issues, it’s time to go in depth into the types of cabling you’ll find on networks and the Network exam. As we’ve discussed, there are three types of physical media that can be used on a network: coaxial cable, twisted-pair cable, and fiber-optic cable. These different media types can be further broken down into different categories and types of cabling, which are either used for specific purposes or provide greater bandwidth. Category 3, 5, 5e, and 6 UTP UTP cabling is the most common type of physical media on networks today. The typical twisted-pair cable for network use contains three or four pairs of wires. As shown in Figure 2.8, each pair of wires contained in the cable is twisted around each other, which helps shield against crosstalk and other forms of EMI. Although the twisted wires do provide a certain amount of immunity from the infiltration of unwanted interference, this doesn’t mean that UTP is the best solution against EMI. Twisted-pair cable is susceptible to interference and should not be used in environments containing large electrical or electronic devices. Because UTP is used for everything from telephone cable to high- speed network cable, the Electrical Industry Association established different categories of UTP. These categories are rated by a number of factors, including the electrical characteristics, conductor size, and twists FIGURE 2.7 MTRJ Connector. CHAPTER 2: Network Media 82 per foot. Because new categories are also an indication of enhancements in the wiring, the higher categories are also new evolutions of twisted- pair. The various categories, which are simply referred to as CAT, are shown in Table 2.6. Table 2.6 Categories of Twisted-Pair Cabling Category Uses CAT 1 Up to 1 Mbps. Voice communication in older analog telephone systems and also used as doorbell wiring. This type of cabling is not suitable for data transmissions. CAT 2 4 Mbps. Low performance cable; used for voice and low-speed data transmission. CAT 3 16 Mbps. Voice communication in newer telephone systems. Rated at 10 MHz, this is the minimum category of UTP that can be used for data transmissions on networks; can be used for Ethernet, Fast Ethernet, and Token Ring. CAT 4 20 Mbps. Used for data and voice transmission; rated at 20 MHz; can be used for Ethernet, Fast Ethernet, and Token Ring. CAT 5 100 Mbps (4 pairs). Typically used for Ethernet networks running at 10 or 100 Mbps. Used for data and voice transmission; rated at 100 MHz; suitable for Ethernet, Fast Ethernet, Gigabit Ethernet, Token Ring, and 155 Mbps ATM. CAT 5e 1000 Mbps. Recommended for all new installations and was designed for transmission speeds of up to 1 Gbps (Gigabit Ethernet). Similar to Category 5, but manufacturing process is refined; higher grade cable than Category 5; rated at 200 MHz; suitable for Ethernet, Fast Ethernet, Gigabit Ethernet, Token Ring, and 155 Mbps ATM. CAT 6 Same as CAT5e, but higher standard. Rated at 250 MHz; suitable for Ethernet, Fast Ethernet, Gigabit Ethernet, Token Ring, and 155 Mbps ATM. CAT 6e Support for 10 Gigabit Ethernet. Similar to Category 6, but is a proposed international standard to be included in ISO/IEC 11801. CAT 7 Not official standard at time of this writing. Still in development. Rated at 600 MHz; suitable for Ethernet, Fast Ethernet, Gigabit Ethernet, Token Ring, and 155 Mbps ATM. FIGURE 2.8 Unshielded Twisted-Pair. Test Day Tip Although there are a number of different categories of UTP, the Network exam expects you to know the details of CAT 3, 5, 5e, and 6 cables. You should only review the other categories to know what is being offered as incorrect choices. 83Recognizing Category 3, 5, 5e, and 6 UTP Category 3 is the minimum grade of cable that supports networking, but it is not the best choice for networks. CAT3 is a voice-grade cable used in phone networks, and its only real benefit beyond being able to sup- port data communication is that it already exists in most office buildings and homes. Regardless of this, CAT 5 or higher should be used in new networks. Most of the UTP cable that’s found in networks today is Category 5. CAT 5 is a multipair performance cable with eight wires (four pairs) that supports higher bandwidth and is typically used for Ethernet networks that run at 10 or 100 Mbps. Until recent enhancements were made to UTP, this grade of cabling was the standard for new network installations. Category 5e is essentially the same as CAT 5 cable, but adheres to more stringent standards that make it as a better candidate for new installations that will use Gigabit Ethernet. It is designed for transmission speeds of up to 1 Gbps and has been made an official standard. Category 6 is another enhancement to the previous grades and provides support for 10 Gigabit Ethernet. It is officially a part of the 568A standard, making it a standard grade of cable for UTP installations. STP As its name says, the difference between the unshielded and shielded variet- ies of twisted-pair is the shield. As shown in Figure 2.9, STP has a shield that’s usually made of aluminum/polyester that resides between the outer jacket and the wires. The shield is designed to keep more interference out, protecting the wires inside from EMI caused by outside sources. STP also uses a much higher quality protective jacket for greater insulation. Coaxial Cable Coaxial (or coax) cable looks like the cable used to bring the cable TV signal to our television. As shown in Figure 2.10, one strand (a solid-core wire) runs down the middle of the cable. Around that Exam Warning Category 1 and 2 of UTP is for voice communications. Category 3 or higher can be used for data communications, but Category 5 or higher should be used. On the exam, you may see these categories abbreviated, so that they use the term CAT for category. Don’t let this confuse you. Plastic Covering Shielding Copper Wire Insulation FIGURE 2.9 Shielded Twisted-Pair. CHAPTER 2: Network Media 84 strand is insulation. Covering that insulation is braided wire and metal foil, which shields against EMI. A final layer of insulation covers the braided wire. Coaxial cable is resistant to the interference and signal weakening that other cabling, such as UTP cable, can experience. In general, coax is bet- ter than UTP cable at connecting longer distances and for reliably supporting higher data rates with less sophisticated equipment. Just because the TV cable is coax does not mean it will work with com- puter networks. Network coaxial cable has very specific requirements, such as the gauge, the impedance, and the attenuation. Thinnet refers to RG-58 cabling, which is a flexible coaxial cable about 1/4 inch thick. Thinnet is used for short-distance communication and is flexible enough to facilitate routing between workstations. Thinnet connects directly to a workstation’s network adapter card using a BNC T-connector and uses the network adapter card’s internal transceiver. 10Base2 refers to Ethernet LANs that use Thinnet cabling. Thicknet coaxial cable can support data transfer over longer distances better than Thinnet can and is usually used as a backbone to connect several smaller Thinnet-based networks. The diameter of a Thicknet cable is about 1/2 inch and is harder to work with than a Thinnet cable. A transceiver is connected directly to Thicknet cable using a connector known as a piercing tap. Connection from the transceiver to the network adapter card is made using a drop cable to connect to the adapter unit interface port connector. 10Base5 refers to Ethernet LANs that use Thick- net cabling. SMF-Optic Cable Optical fibers carry digital data signals in the form of modulated pulses of light. As shown in Figure 2.11, an optical fiber consists of an extremely thin cylinder of glass or optical fiber, called the core, surrounded by a concentric layer of glass, known as the cladding. A cable may contain FIGURE 2.10 Coaxial Cable. Exam Warning Although coax is not as commonly used as it used to be, the Network exam expects you to understand what it is and how it works. You will need to understand the lengths of cabling that can be used with Thinnet and Thicknet coax as well as the transmission speeds. Other Media 85 two fibers per cable – one to trans- mit and one to receive – or a single fiber. However, often, multiple fibers are bundled into the center of the cable. The fiber and cladding can be surrounded by a liquid gel that reflects signals back into the fiber to reduce signal lost, or a plastic spacer surrounded by Kevlar fiber. Each of these components making up the fiber-optic cable is further protected by a plastic covering that encases everything within the cable. There are two different types of fiber-optic cabling that may be used to carry data: SMF and MMF. SMF is optical fiber that’s designed to trans- mit a single beam of light from a laser. The beam of modulated light provides greater bandwidth and allows cable to be run over longer distances. Because of these features, SMF is used for long distance transmissions such as in tele- phone and cable television networks. MMF-Optic Cable MMF is used to carry multiple beams of light at the same time, using a light emitting diode (LED) as a light source. Each of the beams is at a slightly different reflection angle within the core of the fiber. Because the light tends to disperse over distance, MMF is used for connecting locations within relatively short distances. OTHER MEDIA Although the cabling, connectors, and other elements of a network we’ve discussed in this chapter are either traditional components of a network, or have grown to become standard, there are other technologies that are either new, not readily associated with networking, or often forgotten. Nevertheless, elements such as wireless technologies, FireWire, and transceivers are impor- tant to networking. Such media is not only covered on the Network exam, but it is important to the design or development of your network. FIGURE 2.11 Fiber-Optic Cabling. . Ethernet, and Token Ring. CAT 5 100 Mbps (4 pairs). Typically used for Ethernet networks running at 10 or 100 Mbps. Used for data and voice transmission; rated at 100 MHz; suitable for Ethernet,. pairs) that supports higher bandwidth and is typically used for Ethernet networks that run at 10 or 100 Mbps. Until recent enhancements were made to UTP, this grade of cabling was the standard. standard. Category 6 is another enhancement to the previous grades and provides support for 10 Gigabit Ethernet. It is officially a part of the 568A standard, making it a standard grade of cable for UTP installations. STP As