A+ Chapter 4

Direct burial

cable is laid and then covered in earth or cement/concrete. may also need to be armored to protect against chewing by rodents.

Network sniffing

can also be facilitated using a switched port analyzer (SPAN)/mirror port. This means that the sensor is attached to a specially configured port on a network switch. The mirror port receives copies of frames addressed to nominated access ports (or all the other ports).

Metropolitan Area Networks

can be used to mean a specific network type covering an area equivalent to a city or other municipality. It could mean a company with multiple connected networks within the same metropolitan area—so, larger than a LAN but smaller than a WAN.

Conduit

can provide more protection for buried cable runs. Such cable can still be exposed to extreme temperatures and damp conditions, however, so regular PVC cable should not be used.

orthogonal frequency division multiple access" (OFDMA)

can work alongside MU-MIMO to improve client density—sustaining high data rates when more stations are connected to the same access point. Feature of Wi-Fi 6 allowing an access point to serve multiple client stations simultaneously.

MAC

consists of 48 binary digits, making it six bytes in size. A MAC address is typically represented as 12 digits of hexadecimal. Hex is a numbering system often used to represent network addresses of different types. A hex digit can be one of sixteen values: 0-9 and then A, B, C, D, E, F. Each hex digit represents half a byte (or four bits or a nibble). The 12 digits of a MAC address might be written with colon or hyphen separators or no separators at all—for example, 00:60:8c:12:3a:bc or 00608c123abc .

Cat5e

1 Gbps 100 m (328 ft) 1000BASE-TX (Gigabit Ethernet)

Cat6

1 Gbps 100 m (328 ft) 1000BASE-TX (Gigabit Ethernet) 10 Gbps 55 m (328 ft) 10GBASE-T (10G Ethernet)

Cat6A

10 Gbps 100 m (328 ft) 10GBASE-T (10G Ethernet) TIA/EIA standards recommend Cat 6A for health care facilities, with Power over Ethernet (PoE) 802.3bt installations, and for running distribution system cable to wireless access points.

Cat5

100 Mbps 100 m (328 ft) 100BASE-TX (Fast Ethernet)

100BASE-T 1000BASE-T 10GBASE-T

100BASE-T refers to Fast Ethernet over copper twisted pair cabling. Fast Ethernet works at 100 Mbps. 1000BASE-T refers to Gigabit Ethernet over copper twisted pair cabling. Gigabit Ethernet works at 1000 Mbps (or 1 Gbps). 1000BASE-T is the mainstream choice of standard for most LANs. 10GBASE-T refers to a copper cabling standard working at 10 Gbps.

Power over Ethernet (PoE) 802.3af 802.3at (PoE+) 802.3bt (PoE++ or 4PPoE)

802.3af allows powered devices to draw up to about 13 W. Power is supplied as 350mA@48V and limited to 15.4 W, but the voltage drop over the maximum 100m (328 feet) of cable results in usable power of around 13 W. 802.3at (PoE+) allows powered devices to draw up to about 25 W, with a maximum current of 600 mA. 802.3bt (PoE++ or 4PPoE) supplies up to about 51 W (Type 3) or 73 W (Type 4) usable power.

SOHO

A small office home office LAN is a business-oriented network possibly using a centralized server, in addition to client devices and printers, but often using a single networking appliance to provide LAN and Internet connectivity. This is often referred to as a "SOHO router," "Internet router," or "broadband router."

service set identifier (SSID)

Character string that identifies a particular wireless LAN (WLAN). can be up to 32 bytes in length and, for maximum compatibility, should only use ASCII letters and digits plus the hyphen and underscore characters.

Regulatory impacts (5GHz)

Devices operating in the 5 GHz band must implement dynamic frequency selection (DFS) to prevent Wi-Fi signals from interfering with nearby radar and satellite installation Regulatory feature of wireless access points that prevents use of certain 5 GHz channels when in range of a facility that uses radar.

RJ45 connector

Ethernet can be terminated using modular RJ45 connectors. RJ45 connectors are also referred to as "8P8C," standing for eight-position/eight-contact. Each conductor in four-pair Ethernet cable is color-coded. Each pair is assigned a color (orange, green, blue, and 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.

NETWORK INTERFACE CARDS

For the NIC to be able to process the electrical or light signals as digital data, the signals must be divided into regular units with a consistent format. There must also be a means for each node on the local network to address communications to other nodes. Ethernet provides a data link protocol to perform these framing and addressing functions.NETWORK INTERFACE CARDS

power injector

If the switch does not support PoE, a device called (or "midspan") can be used. One port on the injector is connected to the switch port. The other port is connected to the device. The overall cable length cannot exceed 100m.

Collision

If two computers try to send at the same time, there is a collision, and they must wait for a random period before trying again. The more computers there are, the more collisions. The computers contend for a share of the media bandwidth and all communications are half-duplex. Half-duplex means that the computer can send or receive, but not at the same time.

T568A/T568B

In T568A, pin 1 is wired to green/white, pin 2 is wired to green, pin 3 is wired to orange/white, and pin 6 is wired to orange. In T568B, the position of the green and orange pairs is swapped over, so that orange terminates to 1 and 2 and green to 3 and 6. 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.

Multiuser MIMO

In basic 802.11 operation modes, bandwidth is shared between all stations. An AP can communicate with only one station at a time; multiple station requests go into a queue. This means that Wi-Fi networks experience the same sort of contention issues as legacy Ethernet hubs. Wi-Fi 5 products partially address this problem using multiuser MIMO (MU-MIMO). In Wi-Fi 5, downlink MU-MIMO (DL MU-MIMO) allows the access point to use its multiple antennas to send data to up to four clients simultaneously.

managed switches

Larger workgroups and corporate networks require additional functionality in their switches. Switches designed for larger LANs are managed switches . A managed switch will work as an unmanaged switch out-of-the-box, but an administrator can connect to it over a management port, configure security settings, and then choose options for the switch's more advanced functionality. Most managed switches are designed to be bolted into standard network racks. A typical workgroup switch will come with 24 or 48 access ports for client PCs, servers, and printers. These switches have uplink ports allowing them to be connected to other switches.

decibel (dB)

Signal strength is represented as the ratio of a measurement to 1 milliwatt (mW), where 1 mW is equal to 0 dBm. Because 0 dBm is 1 mW, a negative value for dBm represents a fraction of a milliwatt. For example, -30 dBm is 0.001 mW; -60 dBm is 0.000001 mW. Wi-Fi devices are all constrained by regulations governing spectrum use and output only small amounts of power.

Effective isotropic radiated power (EIRP)

Signal strength from a transmitter, measured as the sum of transmit power, antenna cable/connector loss, and antenna gain.

FREQUENCY BAND (US)

The 2.4 GHz band is subdivided into up to 14 channels, spaced at 5 MHz intervals from 2,412 MHz up to 2,484 MHz. Because the spacing is only 5 MHz and Wi-Fi needs 20 MHz channel bandwidth, 802.11b channels overlap quite considerably. This means that interference is a real possibility unless widely spaced channels are chosen (1, 6, and 11, for instance). Also, in the Americas, regulations permit the use of channels 1-11 only, while in Europe, channels 1-13 are permitted, and in Japan, all 14 channels are permitted.

Patch Panels

The cables running through the walls are terminated to insulation displacement connector (IDC) punchdown blocks at the back of the panel. The other side of the patch panel has prewired RJ45 ports. A patch cord is used to connect a port on the patch panel to a port on an Ethernet switch. This cabling design makes it easier to change how any given wall port location is connected to the network via switch ports.

OPTICAL CABLING

The light pulses generated by lasers and LEDs are not susceptible to interference and suffer less from attenuation. can support much higher bandwidth links, measured in multiple gigabits or terabits per second, and longer cable runs, measured in miles rather than feet. consists of an ultra-fine core of glass to convey the light pulses. The core is surrounded by glass or plastic cladding, which guides the light pulses along the core. The cladding has a protective coating called the "buffer." connectors are quite easy to damage and should not be repeatedly plugged in and unplugged. Unused ports and connectors should be covered by a dust cap to minimize the risk of contamination.

Unshielded Twisted Pair (UTP)

The most popular type of network cable is of a copper wire construction is made up of four copper conductor wire pairs. Each pair of insulated conductors is twisted at a different rate from the other pairs, which reduces interference. 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. Most cable segments have a maximum recommended distance of 100 m (328 feet).

RJ11 connector

Twisted-pair can also be used with RJ11 connectors. Unlike the four-pair cable used with Ethernet, RJ11 is typically used to terminate two-pair cable, which is widely used in telephone systems and with broadband digital subscriber line (DSL) modems.

Cable Tester

Two-part tool used to test successful termination of copper cable by attaching to each end of a cable and energizing each wire conductor in turn with an LED to indicate an end-to-end connection.

patch cord

Type of flexible network cable typically terminated with RJ45 connectors. Ethernet patch cords cannot be longer than five meters.

permanent cable

Type of solid network cable typically terminated to punchdown blocks that is run through wall and ceiling spaces.

decibels isotropic (dBi)

Unit for representing the increase in power gained by the directional design of a wireless antenna.

SWITCHES

Unlike a hub, an Ethernet switch can decode each frame and identify the source and destination MAC addresses. It can track which MAC source addresses are associated with each port. When it receives an incoming frame, the switch intelligently forwards it to the port that is a match for the destination MAC address.

Fully shielded cabling

has a braided outer screen and foil-shielded pairs and is referred to as "shielded/foiled twisted pair" (S/FTP). There are also variants with a foil outer shield (F/FTP).

multiple input multiple output" (MIMO)

Use of multiple reception and transmission antennas to boost wireless bandwidth via spatial multiplexing and to boost range and signal reliability via spatial diversity.

multiuser MIMO (MU-MIMO)

Use of spatial multiplexing to allow a wireless access point to support multiple client stations simultaneously.

Plenum

is a void in a building designed to carry heating, ventilation, and air conditioning (HVAC) systems.

Multi-mode fiber (MMF)

has a larger core (62.5 or 50 microns) and is designed to carry a shorter wavelength infrared light (850 nm or 1,300 nm). MMF uses less expensive and less coherent LEDs or vertical cavity surface emitting lasers (VCSELs) and consequently is less expensive to deploy than SMF. However, MMF does not support such high signaling speeds or long distances as single-mode and so is more suitable for LANs than WANs.

Subscriber connector (SC)

has a push/pull design that allows for simpler insertion and removal than fiber channel (FC) connector. 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.

Single-mode fiber (SMF)

has a small core (8-10 microns) and is designed to carry a long wavelength (1,310 or 1,550 nm) infrared signal, generated by a high-power, highly coherent laser diode. 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.

Screened cable

has one thin outer foil shield around all pairs. Screened cable. is usually designated as screened twisted pair (ScTP) or foiled/unshielded twisted pair (F/UTP), or sometimes just foiled twisted pair (FTP).

Wi-Fi 6 (802.11ax)

improves the per-stream data rate over an 80 MHz channel to 600 Mbps. As with Wi-Fi 5, products are branded using the combined throughput of all radios. For example, AX6000 claims nominal rates of 1,148 Mbps on the 2.4 GHz radio and 4,804 Mbps over 5 GHz.

Straight tip (ST)

is a bayonet-style connector that uses a push-and-twist locking mechanism; it is used mostly on older multi-mode networks.

passive test access point (TAP)

is a box with ports for incoming and outgoing network cabling and an inductor or optical splitter that physically copies the signal from the cabling to a monitor port. No logic decisions are made, so the monitor port receives every frame—corrupt or malformed or not—and the copying is unaffected by load.

Coaxial (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), and then a second wire mesh conductor serves both as shielding from EMI and as a ground. F-type connector

HUBS

is a legacy network hardware device that was used to implement the 10BASE-T and 100BASE-T Ethernet cabling designs. This design is referred to as a "star topology" because each end system is cabled to a concentrator (the hub). has a number of ports—typically between four and 48—and each computer is cabled to one port. The circuitry in the hub repeats an incoming transmission from a computer attached to one port across all the other ports. In effect, the computers seem to be attached to the same cable. Each computer attached to a hub receives all the traffic sent by other connected devices. This is referred to as a "collision domain."

Radio Frequency ID (RFID)

is a means of identifying and tracking objects using specially encoded tags. When an RFID reader scans a tag, the tag responds with the information programmed into it. A tag can be either an unpowered, passive device that only responds when scanned at close range (up to about 25 m) or a powered, active device with a range of 100 m. Passive RFID tags can be embedded in stickers and labels to track parcels and equipment. RFID is also used to implement some types of access badge to operate electronic locks.

Near Field Communications (NFC)

is a peer-to-peer version of RFID; that is, an NFC device can work as both tag and reader to exchange information with other NFC devices. NFC normally works at up to two inches (6 cm) at data rates of 106, 212, and 424 Kbps. NFC sensors and functionality are starting to be incorporated into smartphones. NFC is mostly used for contactless payment readers, security ID tags, and shop shelf-edge labels for stock control. It can also be used to configure other types of connections such as pairing Bluetooth devices.

active TAP

is a powered device that performs signal regeneration, which may be necessary in some circumstances. Gigabit signaling over copper wire is too complex for a passive tap to monitor, and some types of fiber links may be adversely affected by optical splitting. Because it performs an active function, the TAP becomes a point of failure for the links during power loss.

Lucent connector (LC)

is 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.

Datacenters

is a whole site that is dedicated to provisioning server resources. Most datacenters are housed in purpose-built facilities. A datacenter has dedicated networking, power, climate control, and physical access control features all designed to provide a highly available environment for running critical applications.

cable stripper

is designed to score the outer jacket just enough to allow it to be removed. Set the stripper to the correct diameter, and then place the cable in the stripper and rotate the tool once or twice. The score cut in the insulation should now allow you to remove the section of jacket.

Wi-Fi 5 (802.11ac)

is designed to work only in the 5 GHz band. A dual band access point can use its 2.4 GHz radio to support clients on legacy standards (802.11g/n). A tri band access point has one 2.4 GHz radio and two 5 GHz radios. Wi-Fi 5 allows up to eight streams, though in practice, most Wi-Fi 5 access points only support 4x4 streams. A single stream over an 80 MHz channel has a nominal rate of 433 Mbps. Wi-Fi 5 also allows wider 80 and 160 MHz bonded channels.

PoE-enabled switch

is referred to as endspan power sourcing equipment (PSE). When a device is connected to a port on a PoE switch, the switch goes through a detection phase to determine whether the device is PoE enabled. If so, it determines the device's power consumption and sets an appropriate supply voltage level. If not, it does not supply power over the port and, therefore, does not damage non-PoE devices.

Aerial cable

is typically strung between two poles or anchors. The ultraviolet (UV) rays in sunlight plus exposure to more extreme and changing temperatures and damp conditions will degrade regular PVC.

Bluetooth

is used to connect peripheral devices to PCs and mobiles and to share data between two systems. Many portable devices, such as smartphones, tablets, wearable tech, audio speakers, and headphones, now use Bluetooth connectivity.

network tap

is used to intercept the signals passing over a cable and send them to a packet or protocol analyzer. Taps are either powered or unpowered:

Loopback Plug

is used to test a NIC or switch port. You can make a basic loopback plug from a 6" cable stub where the wires connect pin 1 to pin 3 and pin 2 to pin 6. When you connect a loopback plug to a port, you should see a solid link LED showing that the port can send and receive. A loopback plug made from a cable stub is unlikely to work with Gigabit Ethernet ports. You can obtain manufactured Gigabit port loopback testers.

Plenum Cable

must not emit large amounts of smoke when burned, be self-extinguishing, and meet other strict fire safety standards. uses treated PVC or fluorinated ethylene polymer (FEP) Data cable rated for plenum use under the US National Electrical Code (NEC) is marked as CMP/MMP on the jacket. General purpose cables are marked CMG/MMG or CM/MP.

Shielded twisted pair (STP)

provides extra protection against interference. Shielded cable is often used for 10G Ethernet and higher within datacenter networks because it is more reliable than UTP. Shielding may also be a requirement in environments with high levels of external interference, such as cable that must be run in proximity to fluorescent lighting, power lines, motors, and generators.

STORAGE AREA NETWORKS

provisions access to a configurable pool of storage devices that can be used by application servers. A SAN is isolated from the main network. It is only accessed by servers, not by client PCs and laptops. SAN clients are servers running databases or applications. Provisioning a shared storage pool as a SAN is more flexible and reliable than using local disks on each server machine. SANs use connectivity technologies such as Fiber Channel and Internet SCSI (iSCSI).

PAN

refers to using wireless connectivity to connect to devices at a range of a few meters. A PAN can be used to share data between a PC and mobile devices and wearable technology devices, such as smart watches. It can also connect PCs and mobiles to peripheral devices, such as printers, headsets, speakers, and video displays. As digital and network functionality continues to be embedded in more and more everyday objects, appliances (the IOT), and clothing, the use of PANs will only grow.

Outside plant (OSP)

s cable run on the external walls of a building or between two buildings. This makes the cable vulnerable to different types of weathering

Wide Area Networks

spans multiple geographic locations. One example of a *** is the Internet, a global network of networks. A company dedicated to facilitating access to the Internet from local networks is called an Internet Service Provider (ISP).

Wi-Fi 6e

standard adds support for a new 6 GHz frequency band. 6 GHz has less range, but more frequency space, making it easier to use 80 and 160 MHz channels.

IEEE 802.11n

standard introduced several improvements to increase bandwidth. It can work over both 2.4 GHz and 5 GHz. Each band is implemented by a separate radio. An access point or adapter that can support simultaneous 2.4 GHz and 5 GHz operation is referred to as "dual band." Cheaper client adapters and many smartphone adapters support only a 2.4 GHz radio. increases reliability and bandwidth by multiplexing signal streams from 2-3 separate antennas. This technology is referred to as " multiple input multiple output" (MIMO). The antenna configuration is represented as 1x1, 2x2, or 3x3 to indicate the number of transmit and receive antennas available to the radio. is now officially designated as Wi-Fi 4.

2.4 GHz

standard is better at propagating through solid surfaces, giving it the longest signal range. does not support a high number of individual channels and is often congested, with both other Wi-Fi networks and other types of wireless technology, such as Bluetooth®. Also, microwave ovens work at frequencies 45 m (150 feet)

5 GHz

standard is less effective at penetrating solid surfaces and so does not support the maximum ranges achieved with 2.4 GHz standards, but the band supports more individual channels and suffers less from congestion and interference, meaning it supports higher data rates at shorter ranges. 30 m (100 feet)

IEEE 802.11g

standard offered a relatively straightforward upgrade path from 802.11b; uses the same encoding mechanism and 54 Mbps rate as 802.11a but in the 2.4 GHz band used by 802.11b and with the same channel layout. This made it straightforward for vendors to design 802.11g devices that could offer backwards support for legacy 802.11b clients.

IEEE 802.11b

standard uses the 2.4 GHz frequency band and was released in parallel with 802.11a. The signal encoding methods used by 802.11b are inferior to 802.11a and support a nominal data rate of just 11 Mbps.

IEEE 802.11a

standard uses the 5 GHz frequency band only. The data encoding method allows a maximum data rate of 54 Mbps. The 5 GHz band is subdivided into 23 non-overlapping channels, each of which is 20 MHz wide.

Unmanaged Switch

switch performs its function without requiring any sort of configuration. You just power it on and connect some hosts to it, and it establishes Ethernet connectivity between the network interfaces without any more intervention. You might find unmanaged switches with four or eight ports used in small networks. There is an unmanaged four-port switch embedded in most of the SOHO router/modems supplied by Internet Service Providers (ISPs) to connect to their networks.

Wireless LANs

uses radios and antennas for data transmission and reception. Most WLANs are based on the IEEE 802.11 series of standards. IEEE 802.11 is better known by its brand name, Wi-Fi. Wi-Fi and Ethernet technologies complement one another and are often used together as segments within the same local network. This allows computers with wired and wireless networking adapters to communicate with one another.

Toner Probe

which is used to identify a cable from within a bundle. This may be necessary when the cables have not been labeled properly. The tone generator is connected to the cable using an RJ45 jack and applies a continuous audio signal on the cable. The probe is used to detect the signal and follow the cable over ceilings and through ducts or identify it from within the rest of the bundle.