Wired Networks
USB Optical Drive
—most ultraportable laptops no longer feature optical drives as they cannot fit within the ultrathin chassis.—most ultraportable laptops no longer feature optical drives as they cannot fit within the ultrathin chassis.
USB to RJ-45
—provide an Ethernet port for a laptop or mobile device. Ultrathin laptops often omit a built-in RJ-45 port as it is too tall to fit in the chassis.
USB to Wi-Fi/Bluetooth
—this might be used to upgrade to a better Wi-Fi standard than the laptop's built-in adapter. Most dongles will also function as a Bluetooth adapter. Some Wi-Fi dongles are compact but those lacking large antennas may not perform well; the drawback of large antennas is, of course, that they protrude significantly.
Fiber Optic Cabling and Connectors: Connectors
A number of connectors have been designed for use with fiber optic cabling. Some types are more popular for multi-mode and some for single-mode. Connectors for MMF are usually color-coded beige while those for SMF are blue. The core of each connector is a ceramic or plastic ferrule that ensures continuous reception of the light signals. Straight Tip (ST)—A bayonet-style connector that uses a push-and-twist locking mechanism; used mostly for multi-mode networks. Subscriber Connector (SC)—Connector with a push/pull design that allows for simpler insertion and removal than FC. There are simplex and duplex versions, though the duplex version is just two connectors clipped together. It can be used for single- or multi-mode. Lucent or Local Connector (LC)—A small form factor connector with a tabbed push/pull design. LC is similar to SC but the smaller size allows for higher port density.
Plenum Cable
A plenum space is a void in a building designed to carry Heating, Ventilation, and Air Conditioning (HVAC) systems. Plenum space is typically a false ceiling, though it could also be constructed as a raised floor. As it makes installation simpler, this space has also been used for communications wiring in some building designs. Plenum space is an effective conduit for fire, as there is plenty of airflow and no fire breaks, such as walls and doors. If the plenum space is used for heating, there may also be higher temperatures. Therefore, building regulations require the use of fire-retardant plenum cable in such spaces. Plenum cable must not emit large amounts of smoke when burned, be self-extinguishing, and meet other strict fire safety standards.General purpose (non-plenum) cabling uses PVC (polyvinyl chloride) jackets and insulation. Plenum-rated cable uses treated PVC or Fluorinated Ethylene Polymer (FEP). This can make the cable less flexible but the different materials used have no effect on bandwidth. Data cable rated for plenum use under the US National Electrical Code (NEC) is marked CMP/MMP. General purpose cables are marked CMG/MMG or CM/MP.
Coaxial Cabling and Connectors pt 2
Coax cabling is also available with tri- or quad-shielding for better resistance to EMI and eavesdropping. In most cases, BNC (alternately Bayonet-Neill-Concelman, British Naval Connector, or Barrel Nut Connector) connectors are crimped to the ends of the cable. The impedance of the connector must match the cable type (50 or 75 ohm).Coax installations also use screw-down F-connectors. A broadband cable service, for example, is likely to use the F-connector for drop cables.As an Ethernet LAN media product (10BASE-5/Thicknet and 10BASE-2/Thinnet), coax could support 10 Mbps with cable lengths of up to 500 m and 185 m, respectively. Coax is considered obsolete in terms of LAN applications but is still widely used for CCTV networks and as drop cables for cable TV (CATV) and Internet access, where it can support higher bandwidths but at reduced range. In a Hybrid Fiber Coax (HFC) network, coax cable links the fiber optic trunk serving the whole street to the cable "modem" installed in the customer's premises. Coax suffers less from attenuation than twisted pair but is generally bulkier and more difficult to install.
Coaxial Cabling and Connectors
Coaxial, or coax cable is a different type of copper cabling, also carrying electrical signals. Where twisted pair uses balancing to cancel out interference, coax uses two conductors that share the same axis. The core signal conductor is enclosed by plastic insulation (dielectric) then a second wire mesh conductor serves both as shielding from EMI and as a ground.Coax cables are categorized using the Radio Grade (RG) "standard." The Radio Grade (or Radio Guide) classifications were developed by the US military but are no longer actively maintained by any sort of standards body. They do not prescribe the quality of coax cabling but categorize it by the thickness of the core conductor and the cable's characteristic impedance.RG-6 cable has a thicker core conductor for better signal quality and is often used as a drop/patch cable for modern Cable Access TV (CATV) and broadband cable modems. RG-59 cable has a thinner core conductor and was used as a drop cable for older CATV/cable modem installs and is also used for CCTV cabling.
Fiber Optic Cabling and Connectors
Copper wire carries electrical signals, which are subject to interference and attenuation. Light signals are not susceptible to interference, cannot easily be intercepted (eavesdropped), and suffer less from attenuation. Consequently, fiber optic cabling can support much higher bandwidth, measured in multiple gigabits or terabits per second, and longer cable runs, measured in miles rather than feet. An optical fiber consists of an ultra-fine core of glass to carry the light signals surrounded by glass or plastic cladding, which guides the light pulses along the core, and a protective coating called the buffer. The fiber optic cable is contained in a protective jacket and terminated by a connector.
Fiber Optic Cabling and Connectors: Cables
Fiber optic cables fall into two broad categories: single-mode and multi-mode: Single-Mode Fiber (SMF) has a small core (8-10 microns) and is designed to carry a long wavelength, near infrared (1310 or 1550 nm) light signal, generated by a laser. Single-mode cables support data rates up to 10 Gbps or better and cable runs of many kilometers, depending on the quality of the cable and optics. Multi-mode (MMF) has a larger core (62.5 or 50 microns) and is designed to carry a shorter wavelength light (850 nm or 1300 nm) transmitted in multiple waves of varying length. MMF uses less expensive optics and consequently is less expensive to deploy than SMF. However, it does not support such high signaling speeds or long distances as single-mode and so is more suitable for LANs than WANs.
Wired Networks OBJECTIVE COVERED Explain basic cable types, features, and their purposes.
In this topic, you will identify suitable cabling options for different types of wired networks.
Expansion Options
Laptops ship with standard wired ports for connectivity. The ports are usually arranged on the left and right edges. Older laptops might have ports at the back of the chassis. There will be at least one video port for an external display device, typically HDMI or DisplayPort/Thunderbolt, but possibly VGA or DVI on older laptops. There will also be a number of USB Type A ports and one or more USB Type C ports on a modern laptop, one of which may also function as a Thunderbolt port. Other standard ports include microphone and speaker jacks and RJ-45 (Ethernet) for networking. Finally, a laptop might come with a memory card reader. USB provides a simple means of adding or upgrading an adapter without having to open the laptop chassis. USB adapters (or "dongles") can provide a wide range of functionality:
Twisted Pair Cabling and Connectors
Most cabled LANs use a type of copper wire called twisted pair as transmission media.
Fiber Optic Cabling and Connectors: Patch cords
Patch cords for fiber optic can come with the same connector on each end (ST-ST, for instance) or a mix of connectors (ST-SC, for instance). Fiber optic connectors are quite easy to damage and should not be repeatedly plugged in and unplugged.
Cat Standards
The number of twists is one factor in determining the speed and transmission limitations of the cable. Twisted pair cable is rated for different Ethernet applications according to "Cat" specifications, defined in the TIA/EIA-568-C Commercial Building Telecommunications Cabling StandardCat 5 cable is no longer available. Cat 5e is tested at 100 MHz—as Cat 5 was—but to higher overall specifications for attenuation and crosstalk, meaning that the cable is rated to handle Gigabit Ethernet throughput. Cat 5e would still be an acceptable choice for providing network links for workstations. Cat 6 can support 10 Gbps, but over shorter distances. Cat 6A is an improved specification cable with the ability to support 10 Gbps over 100 m. It is mostly deployed in data centers or as backbone cabling between servers and network appliances.
Wiring Standards for Twisted Pair
Twisted pair cabling for Ethernet is terminated using modular RJ-45 connectors. RJ-45 connectors are also referred to as 8P8C, standing for 8-position/8-contact. Each conductor in 4-pair Ethernet cable is color-coded. Each pair is assigned a color (Blue, Orange, Green, or Brown). The first conductor in each pair has a predominantly white insulator with stripes of the color; the second conductor has an insulator with the solid color.The ANSI/TIA/EIA 568 standard defines two methods for terminating RJ-45 connectors: T568A and T568B. The wiring for T568A is shown in the previous figure. In T568B, pin 1 is wired to Orange/White, pin 2 is wired to Orange, pin 3 is wired to Green/White, and pin 6 is wired to Green or, put another way, the orange and green pairs are swapped over.A normal—or straight through—Ethernet cable is wired with the same type of termination at both ends. Using T568A at one end and T568B at the other creates a crossover cable. Crossover cables were once used to connect computers directly, but Gigabit Ethernet interfaces can perform the crossover automatically, even if standard cable is used.Organizations should try to avoid using a mixture of the two standards. It is difficult to say whether one is more prevalent than the other. T568A is mandated for US government premises and by the residential cabling standard (TIA 570).
Unshielded Twisted Pair Cable
Unshielded Twisted Pair (UTP) is the type of cabling most widely used for computer networking. With the type of UTP used for Ethernet, the cable contains four copper conductor "pairs." Each conductor has an insulating sheath. Each pair of conductors is twisted, which reduces interference between the wires (crosstalk) and interference from other electromagnetic sources, referred to as Electromagnetic Interference (EMI). Each pair is twisted at a different rate to further reduce interference. The signals sent over each pair are balanced. This means that each wire carries an equal but opposite signal to its pair. This is another factor helping to identify the signal more strongly against any source of interference. The four pairs are covered by a protective outer jacket. The insulation sheaths and jacket are usually made of (PVC). UTP works well where there are no powerful interference sources, but the electrical signaling method has limited range. The signal is said to suffer from attenuation, meaning that it loses power quickly over long ranges (above 100 m).
Shielded Twisted Pair (STP)
When twisted pair cabling was first used in networks based on IBM's Token Ring product, it was usually shielded to make it less susceptible to interference and crosstalk. Each pair was surrounded by a braided shield. This cable construction is referred to as Shielded Twisted Pair (STP). STP is bulky and difficult to install, so where a degree of protection from interference is required, modern twisted pair cabling installations use screened cables, meaning a shield positioned around all pairs. There are many different ways of designating different types of shielding. Most Cat 5e/6/6A cable is available in shielded variants, notably F/UTP and U/FTP: F/UTP—with a foil screen around all pairs, often also designated ScTP. U/FTP—with foil shielding for each pair. Legacy STP cable could be more complex to install as it required bonding each element to ground manually but modern screened and shielded solutions (using appropriate cable, connectors, jacks, and patch panels) reduce this complexity by incorporating grounding within the design of each element.