Network+ Chapter 2

Difference between LC and MTRJ?

LC has a single connector with two ends keeps the two cables in place MTRJ has a single connector with one end holds both cables.

What is LEC?

Local exchange carrier

What is MDF?

Main distribution frame (MDF) It is a frame or rack that is used to interconnect and manage telecommunication wiring in a building. It functions like an old-time telephone switchboard, where operators used connecting wires to route telephone calls. Today's MDF describes the room that houses the traditional MDF along with networking patch panels. Often, rack mounted equipment is also housed in an MDF.

Core diameter of a single mode fiber?

The core diameter is around 8-10.5 microns.

What causes attenuation with copper cables?

The longer the cable, the more attenuation. For this reason, it is important never to exceed the maximum cable length defined by the networking architecture. Cables at a higher temperature experience more attenuation than cables at a lower temperature.

What is T568 A&B?

They are the two Telecommunications Industry Association (TIA) standards for creating straight-through cables.

What is a straight through cable used for?

To connect computers to a hub or switch.

Why do you want to preserve a twist in twisted pair?

To prevent cross talk.

What is UTP?

UTP stands for unshielded twisted pair. UTP cables are easy to work with and less expensive than shielded cables.

What is a 110 Block used for?

A 110 block is a punch down block used to connect individual wires together. 110 blocks are used primarily for telephone applications and small networks. They are preferable over 66 blocks in high-speed networks because the introduce less crosstalk.

What is a 66 Block used for?

A 66 block is a punch down block used to connect individual copper wires together 66 blocks are used primarily for telephone applications.

What does a cable certifier used for?

A cable certifier is a multi-function tool that verifies that a cable or an installation meets the requirements for a specific architecture implementation. For example, you would use a certifier to verify that a specific drop cable meets the specifications for 1000BaseT networking. Certifiers can also validate the bandwidth capabilities of network interface cards and switches. Many can detect the duplex settings of network devices.

What is TDR?

A time-domain reflectometer is a special device that sends electrical pulses on a wire in order to discover information about the cable. The TDR measures impedance discontinuities (the echo received on the same wire in response to a signal on the wire). The results of this test can be used to identify several variables: Estimated wire length Cable impedance The location of splices and connectors on the wire The location of shorts and open circuits

Advantages and Disadvantages of coaxial cable?

Advantages Highly resistant to EMI (electromagnetic interference) Highly resistant to physical damage Disadvantages Inflexible construction (more difficult to install) Unsupported by newer networking standards

What is Open Impedance Mismatch?

Also known as ECHO Impedance is the measure of resistance within the transmission medium. Impedance is measured in ohms (Ω). All cables must have the same impedance rating. The impedance rating for the cable must match the impedance of the transmitting device. Impedance is mostly a factor in coaxial cables used for networking. Be sure to choose cable with the correct rating (50 or 75 ohm) based on the network type. Never mix cables with different ratings. When signals move from a cable with one impedance rating to a cable with another rating, some of the signal is reflected back to the transmitter, distorting the signal. With video (cable TV), impedance mismatch is manifested as ghosting of the image. Cable distance does not affect the impedance of the cable.

What is the difference between a short and a open circuit?

An electrical short occurs when electrical signals take a path other than the intended path. Shorts occur when two wires touch; this can be caused by worn wire jackets, crushed wires, or a metal object piercing two or more wires An open circuit is when a cut in the wire prevents the original signal from reaching the end of the wire. An open circuit is different from a short in that the signal stops (electricity cannot flow because the path is disconnected).

What is OTDR?

An optical time-domain reflector performs the same function as a TDR, but is used for fiber optic cables. An OTDR sends light pulses into the fiber cable and measures the light that is scattered or reflected back to the device. The information is then used to identify specifics about the cable: The location of a break Estimated cable length Signal attenuation (loss) over the length of the cable

What is APC?

Angled physical contact (APC) polishing is used to reduce back reflection as much as possible. An APC connector has an eight-degree angle cut into the ferrule, which prevents reflected light from traveling back down the fiber. Any reflected light is bounced out into the cable cladding instead.

What is attenuation?

Attenuation is the loss of signal strength from one end of a cable to the other.

What is Cross Talk?

Crosstalk is interference that is caused by signals within the twisted pairs of wires There are several forms of crosstalk: Near-end crosstalk (NEXT) is measured on the same end as the transmitter. For example, when a signal is sent on one wire pair, near-end crosstalk measures the interference on an adjacent wire pair at the same connector end. Far-end crosstalk (FEXT) is measured on the end without the transmitter. For example, when a signal is sent on one wire pair, far-end crosstalk measures the interference on an adjacent wire pair at the opposite connector end. Alien crosstalk is introduced from adjacent, parallel cables. For example, a signal sent on one wire pair causes interference on a wire pair that is within a separate twisted pair cable bundle.

Number of wires per connector in a ST

Each wire has a separate connector.

Number of wires per connector on a SC

Each wire has a separate connector.

What is a crossover cable used for?

If a network devices such as a hub or switch does not have an uplink port, use a crossover cable when connecting it to another network device. You can also connect one computer directly to another using a crossover cable.

What is a Patch Panel used for?

In an MDF or IDF, punch down blocks are rarely used for network cabling. Instead, twisted pair cables are terminated at a patch panel.

What is PC?

Physical contact (PC) polishing is usually used with single-mode fiber. The ends of the fiber are polished with a slight curvature so that when the cable end is inserted into the connector, only the cores of the fiber actually touch each other

What is the difference between PVC and Plenum Cable?

Plenum rated cables use insulation that is fire resistant and non-toxic when burned.

What is PoE?

Power over Ethernet PoE technologies allows network cables to carry electrical power. This is helpful for remote devices where no external power is available.

Coaxial cable grades?

RG-58 10Base2 Ethernet networking (also called thinnet) 50 ohms RG-59 Cable TV and cable networking 75 ohms RG-6 Cable TV, satellite TV, and cable networking 75 ohms. Can be used with longer distances than RG 59 rated cable.

What is the difference between reflection and refraction?

Reflection: A measurable amount of light is reflected when it hits the ends of the cable. Much of a cable's reflection loss occurs at each cable connection. When the light hits the boundary between the core and the cladding, it is reflected back into the core. There is minor loss to the signal when this occurs, but it contributes to overall signal loss. Refraction: If the light hits the boundary between the core and the cladding at too steep of an angle, the light is refracted into the cladding instead of reflected back into the core, causing signal loss. Some fiber optic cables are doped with impurities near the edge of the fiber so that the signals are bent instead of reflected back to the center of the core. The loss due to this refraction is minor when compared with the benefits of confining the light to the center of the core.

What is Riser Cable?

Riser rated cables are designed for installations that run between floors. Riser requirements are not as strict as plenum requirements Plenum rated cables can be used in riser spaces. Riser rated cables must never be used in plenum spaces.

What is STP?

STP stands for shielded twisted pair. Shielding is electrically conductive foil or braided material that is wrapped around pairs of wires, around the overall cable, or both. Shielding helps to minimize crosstalk. The main purpose of shielding is to minimize the effects of EMI from external sources, such as fluorescent light ballasts.

What is Dmarc?

Short for demarcation point It is the line that marks the boundary between the telco equipment or cable and your private network or telephone system. In businesses, the demarc is typically located on the bottom floor of a building, just inside the building, and identified by an orange plastic cover on the wiring component. In residential buildings, the demarc is often a small box on the outside of the house.

What is IDF

Short for intermediate distribution frame. It's a cable rack that interconnects and manages the telecommunications wiring between an MDF and workstation devices. Cables entering a building run through a centralized MDF, then each individual IDF and then on to specific workstations.

What is a Smart Jack?

Smartjacks are maintained by the LEC. Smartjacks are typically used for more complex services, such as a T1 line. Smartjacks can provide signal conversions, buffer signals, and regenerate signals. Smartjacks may provide diagnostic capabilities for the LEC.

What is ORL?

Stands for Optical Return Loss It's when some of the light that is lost is reflected directly back down the cable, toward the source. It can corrupt the data being transmitted and even damage the transmitter. Polishing can help prevent this.

What is SPC?

Super physical contact (SPC) and ultra physical contact (UPC) polishing use a higher grade of polish and have more of a curvature than PC polishing, further reducing ORL reflections.

ST Connector?

Used with single-mode and multi-mode cabling. Has a keyed bayonet-type connector. Also called a push-in and twist connector. Nickel plated with a ceramic ferrule to ensure proper core alignment and prevent light ray deflection. Mnemonics are Set-and-Twist or Straight Tip.

SC Connector?

•Used with single-mode and multi-mode cabling. Has a push-on/pull-off connector that uses a locking tab to maintain connection. Uses a ceramic ferrule to ensure proper core alignment and prevent light ray deflection. Mnemonics are Set-and-Click or Square Connector.