Messer - 2. Infrastructure Flashcards
What are the two primary types of copper cabling used in networking, and which is more common?
coaxial and twisted pair (more common)
What is twisted pair cabling?
Cabling that consists of twisted pairs of wires, bundled together into a common jacket. Each pair in the cable
works as a team either transmitting or receiving data.
What is the benefit of using a pair of twisted wires rather than a single wire?
It reduces a specific type of interference, called crosstalk. The more twists per foot, the less crosstalk.
What are the two types of twisted pair cabling, and which is more common?
Shielded twisted pair (STP) and
Unshielded twisted pair (UTP) (more common)
What is the difference between STP and UTP cabling?
Shielded twisted pair (STP) contains shielding to protect against EMI. The extra shielding may surround the entire cable and/or the individual pairs of wires inside the cable.
Explain how STP cabling is labeled (i.e. the abbreviations used and the format of the specs you might see on a cable)
- U = Unshielded
- S = Braided shielding
- F = Foil shielding
(Overall cable shielding) / (individual pairs shielding) TP [for twisted pair]
[Note that braided shielding is only used for external cable. Never on inside wires]
What does it mean if you see the following on a cable?
F/UTP
Foil shielding around the cable and no shielding around the pairs
What does it mean if you see the following on a cable?
S/UTP
Braided shielding around the cable and no shielding around the pairs
What does it mean if you see the following on a cable?
SF/UTP
Braided and foil shielding around the cable and no shielding around the pairs
What does it mean if you see the following on a cable?
S/FTP
Braided shielding around the cable and foil shields around each wire pair inside
What does it mean if you see the following on a cable?
F/FTP
Foil shielding around the cable and foil shields around each wire pair inside
What does it mean if you see the following on a cable?
U/FTP
No shielding around cable, but foil shields around each wire pair inside
What are the 6 cable categories we need to know, their max supported ethernet standard, and max supported distance?
CAT 3 10BASE-T CAT 5 100BASE-TX, 1000BASE-T CAT 5e 100BASE-TX, 1000BASE-T CAT 6 10GBASE-T CAT 6a 10GBASE-T Cat 7 10GBASE-T
Maximum distance for all cables is 100 meters. However, CAT 6 is only 37-55 meters when using 10GBASE-T.
For max supported standards, remember there are three groupings: Cat 3, the two CAT 5s, and then higher.
What do the letters mean in CAT 5e and CAT 6a?
enhanced
augmented
What’s the minimum cable standard used nowadays?
CAT 5e (CAT 3 and CAT 5 are no longer available)
What is plenum-rated cable and why is it necessary?
A fire-rated cable made of either fluorinated ethylene polymer (FEP) or low-smoke polyvinyl chloride (PVC).
Necessary if you’re running cable in a plenum (an active, circulating airspace used by some HVACs) due to the smoke and toxic fumes caused by traditionally used polyvinyl chloride (PVC) cable jackets.
[Note: It may not be as flexible or have the same bend radius as regular cable]
Describe the internals of a coaxial cable, and the origins of the term “coaxial.”
Contains a central conductor wire (usually copper) surrounded by an insulating material, which, in turn, is surrounded by a braided metal shield. The cable is referred to as coaxial (coax for short) because the center wire and the braided metal shield share a common axis or centerline
Describe the two types of coaxial cable we need to know.
RG-59 - Used primarily for cable TV rather than networking. But also patch cables. Not good for long distances. Its thinness and the intro of digital cable motivated move to RG-6.
RG-6 - Used in TV / digital cable, and high-speed Internet over cable. More robust than RG-59, it’s the predominant cabling used today.
What are the six types of copper connectors we need to know?
RJ-11 RJ-45 BNC DB-9 DB-25 F-connector
What is a coupler?
Synonym for connector
Describe RJ-11 and RJ-45 connectors.
RJ-11 (Registered Jack) connectors are the small plastic connectors used on traditional phone line cables. Also known as 6 position, 2 conductor (6P2C).
RJ-45 connectors are used with twisted-pair cabling in ethernet networks. Look similar to RJ-11, but a little bigger. Also known as 8 position, 8 conductor (8P8C).
Describe a BNC connector.
aka. Bayonet Neill-Concelman
Associated with coaxial media and 10BASE2 networks. BNC connectors are not as common as they previously were, but they still are used on some networks (e.g. DS3 WAN links), older network cards, and older hubs. Common BNC connectors include a barrel connector, T-connector, and terminators.
Can be rigid, bulky, difficult to work with.
[Not to be confused with F-connector]
Describe DB-9 and DB-25 connectors.
aka RS-232 (Recommended Standard) connectors. Used for serial communication between computers and peripheral devices such as modems, mice, and keyboards. Commonly used as a configuration port on network devices. (i.e. Serial console interface for routers, switches, etc.)
[Connectors are in the shape of letter “D.” Numbers represent how many pins / slots are on connector]
Describe an F-connector.
A threaded, screw-on connections used to attach coaxial cable to devices. In the world of modern networking, F-type connectors are most commonly associated with connecting Internet modems to cable or satellite ISP equipment. However, F-type connectors are also used to connect to some proprietary peripherals. This includes RG-59 and RG-6 cables.
[This is what we’ve used when plugging cable into router or television]
Unlike copper cable, which communicates via _______, optical fiber communicates via ________.
electrical signal
wavelengths of light (i.e. visible spectrum)
What are three major benefits of optical fiber over copper cabling?
1) Sending electrical signal over copper creates radio frequency (RF) interference that is easy to tap / monitor
2) Copper is vulnerable to RF interference from outside
3) Fiber can transmit over longer distances (i.e. kilometers v. hundreds of meters) because light signal slower to degrade than electrical
What are the key differences between multimode v. single-mode fiber?
Multimode fiber:
- Short-range communication (up to 2km)
- Inexpensive light source (i.e. LED)
Single-mode fiber
- Long-range communication (up to 100 km w/o processing)
- Expensive light source (i.e. laser)
[Careful: Easy to think “multi” means better]
Explain origins of terms multi-mode / single-mode fiber.
Called multimode because core of fiber is larger than wavelength of light. As signal travels down fiber, it disperses and creates multiple modes (i.e. beams?) of signal.
In single-mode, fiber is much narrower than core of multi-mode, allowing us to send light signal in a single, straight light beam. (Which is why signal degrades slower / travels further.)
Explain the difference between UPC and APC.
Within the various types of fiber connectors (e.g. ST, SC, LC, MT-RJ, etc), you can choose ones that are either angle polished connectors (APC) or ultra polished connectors (UPC).
UPC connectors have an endface polished at a zero-degree angle (flat), whereas APC is eight degrees, which minimizes signal loss. (Professor Messer uses analogy of pointing flashlight through a window. Pointing at an angle creates less reflection.)
[Mike Meyers says the “P” in acronyms is technically “physical” rather than “polished”]
Name the four commonly used optical fiber connectors.
ST, SC, LC, MT-RJ
Describe an ST connector.
- aka. Straight Tip
- Bayonet connector (push and half-twist to lock it in)
- Rounded connector at end
- Rather long ferrule that sticks out (easy to spot)
[Think “ST” for “sticks out”. But note that SC also sticks out a little]
Describe an SC connector.
-aka. Square / Subscriber / Standard Connector
Push and pull out (no twisting like bayonet)
-Plastic keys to ensure exact fit
-Round Ferrule at end that sticks out a little
[Remember “SC” sound for “square”. But note that LC is also square, but with large flange on top]
Describe an LC connector.
- aka. “Little” / Lucent / Local Connector
- Squarish but with large locking mechanism (similar to RJ-45)
[Remember “L” for large flange on top. Although ironically called “Little Connector”. Like a fat guy named “Little John,” I guess]
Describe an MT-RJ connector
- aka Mechanical Transfer Registered Jack or Media Termination - Recommended Jack
- Very small form factor that fits two fibers (send and receive)
- About the size of an RJ-45 connector (Ethernet)
- Very popular
[Unlike other fiber connectors, has two pins / prongs / ferrules instead of one]
What are T568A and T568B?
Two wiring standards for terminating copper cables. T568B is what we use on today’s networks
What’s important to remember when using T568A / T568B cabling?
Pick one standard and stick to it. You can’t terminate one side of the cable with 568A and other with 568B. Will cause problems, especially on Gigabit network.
If you aren’t consistent you might end up swapping the sending and receiving wires (known as TX/RX reversed) and inadvertently
create a crossover cable.
In terms of internal wiring, what’s the difference between T568A and T568B?
Only difference is that GREEN and ORANGE wires are swapped in the two standards.
(e.g. In 568A, pin 1 is white and green. In 568B, pin 1 is white and orange. Think “GO”)
Describe the difference in how straight-through and crossover cables are used.
Straight-through cables are used to connect DIFFERENT types of devices (e.g. host to client, workstation to switch, hub to switch).
Crossover cables are used to connect SAME types of devices (e.g. host to host, workstation to workstation, or switch to switch).
Note: A crossover cable can be used to directly network two PCs without using a hub or switch. (The cable performs the function of the switch.)
[Careful: A bit unintuitive that crossover is used for same type of device]
How can you tell if a cable is straight-through or crossover by looking at it?
Place the connectors side-by-side facing the same direction. If wires are in same order on both connectors, it’s a straight-through cable.
What is Auto MDI-X?
A feature on newer Ethernet devices (e.g. network cards, routers) which automatically detects whether incoming signal is straight-through or crossover, and adjust accordingly.
What is a patch panel?
Found in a telecommunications closet, it’s a freestanding or wall-mounted unit with a number of female (e.g. RJ-45) port connections on the front. (Looks like a wall-mounted hub w/o the LEDs.) On the back, a punchdown block with permanent connections to horizontal cabling. Often a 66 block or nowadays the more common 110 block.
The patch panel provides a connection point between network equipment, such as hubs and switches, and the ports to which PCs are connected, which normally are distributed throughout a building.
What is the alternative to a patch panel, and why is a patch panel preferable?
You can run cables directly between systems and a hub or switch, but it’s not as easy, flexible, or tidy.
With a patch panel, you can simply move the RJ45 cable to appropriate place on switch / interface. If there’s a new employee, you only need to add a new cable from patch panel to networking equipment. Makes moves, adds, and changes very easy. (You’re also less likely to damage cabling by moving it.)
What tool is used for connecting wires to a 66 block or 110 block?
Punchdown tools are used to attach twisted-pair network cable to connectors within a patch panel. Specifically, they connect twisted-pair wires to the IDC.
What’s the difference between 66 block and 110 block?
66 blocks are generally used for voice and Cat3 data. 110 blocks are the newer, higher-speed technology, generally used for Cat5 and Cat6 data. They support higher frequencies and suffer less crosstalk.
(66 blocks were approved for Cat5 and greater, but not really suitable for anything greater than 10BASE-T due to crosstalk problems. Although there are specialized exceptions.)
What is an FDP?
A fiber distribution panel (FDP). Like a patch panel, it’s used to provide a connection point between network equipment. The difference between the two is that the FDP is a cabinet intended to provide space for termination, storage, and splicing of fiber connections.
What is the difference between an MDF and IDF?
Typically, the main distribution frame (MDF) is a closet / room that stores a building’s demarc, telephone cross-connects, and LAN cross-connects.
An intermediate distribution frame (IDF) room is what we typically think of as a telecommunications closet / room, which contains patch panels, punchdown blocks, and serves individual floors.
(According to Meyers, these concepts are just ideals. Not always the case that you have a single MDF and multiple IDFs, or that these are even separate.)
[These terms are not in Messer vids from what I can see]
What is a network transceiver?
Provides a modular interface for network devices, allowing them to easily adapt to various copper or fiber optic standards. Transceivers can be a stand-alone component (kinda looks like a thumb drive) that gets plugged into a device, or they may be built directly into a network card, switch, router, modem, media converter, etc.
Called transceiver because it’s responsible for both transmitting and receiving (i.e. it place signals onto network media and also detect incoming signals on same wire).
[Not 100% sure how transceivers are different from media converters. From what I gather, media converters may contain an embedded transceiver]
What are two ways that network transceivers communicate?
Duplex communication - Two fibers. One transmits, other receives.
Bi-Directional (BiDi) communication - Single fiber transmits and receives. Significant cost savings by cutting number of required fiber runs in half, but network must support it.
[Careful: Naming may be a bit unintuitive here. ]
What are five types of transceivers?
GBIC, SFP, SFP+, QSFP, QSFP+
What is GBIC?
Gigabit Interface Converter. An early transceiver standard commonly found on Gigabit and fiber channel networks. Offers both copper and fiber support.
What are SFP and SFP+?
Small Form-Factor Pluggable. Transceiver standard that replaced GBIC. Does the same thing, but smaller form-factor.
SFP - Commonly used to provide 1 Gbit/s fiber. RJ45 SFPs also available w/ copper connectors
SFP+ - Enhanced SFP w/ much higher data rates. Supports data rates up to 16 Gbit/s. Common with 10 Gigabit Ethernet.
What are QSFP and QSFP+?
Quad Small Form-Factor Pluggable. Transceiver standard for very high speed networking. Basically four SFPs put into a single transceiver, offering cost saving in fiber and equipment.
QSFP - 4-channel SFP = Four 1 Gbit/s = 4 Gbit/s
QSFP+ - 4-channel SFP+ = Four 10 Gbit/s = 40 Gbit/sec
(Both also available with BiDi, adding additional efficiency)
What are the five ethernet standards we need to know?
100BaseT 1000BaseT 1000BaseSX 1000BaseLX 10GBaseT
1000Base standards are more commonly called what?
Gigabit Ethernet
Describe 100BaseT (e.g. speed, distance, cable type)
Called “Fast Ethernet,” because seemed fast compared to 10BaseT. New installs aren’t using this anymore.
Speed: 100 Mbps
Distance: 100 meters (between hub/switch and node)
Cable Type: Cat 5 or better UTP or STP (copper) cabling with RJ-45/8P8C connectors
Describe 1000BaseT (e.g. speed, distance, cable type)
Gigabit ethernet standard that most people are now using.
Speed: 1000 Mbps (1 Gbps)
Distance: 100 meters
Cable Type: Cat5 or better UTP or STP (copper) (Cat 3, 4, and 5 are deprecated from TIA-568, so we now use Cat 5e)
[Notice: Speed greater than 100BaseT, but cable type and distance are essentially the same. Speed difference in part because it uses all four pairs of wire instead of two]
Describe 1000BaseSX (e.g. speed, distance, cable type)
One of the two fiber ethernet standards we need to know. Uses NIR (near infrared) light wavelength. 2-5x distance of copper.
Speed: 1000 Mbps (1 Gbps)
Distance: 200 meters to 500 meters, depending on fiber type
Cable Type: Usually over multi-mode fiber
[Think “S” for shorter wavelength light than LX, and shorter distance]
Describe 1000BaseLX (e.g. speed, distance, cable type)
One of the two fiber ethernet standards we need to know. Uses long wavelength laser. 5.5-50x distance of copper.
Speed: 1000 Mbps (1 Gbps)
Distance: 550 meters (multi-mode) to 5 km (single-mode)
Cable Type: multi-mode or single-mode fiber
[Think “L” for laser, and longer wavelength light than SX, and longer distance]
Describe 10GBaseT (e.g. speed, distance, cable type)
High-throughput copper standard. Uses 500 MHz frequency inside cable, well above 125 MHz for Gigabit ethernet.
[Note: Faster than earlier copper standards, but distance limitations remain the same]
Speed: 10 Gbps
Distance: 55 meters (Cat 6) or 100 meters (Cat 6A or Cat7)
Cable type: Cat 6, 6A, or 7
[TIP: If standard ends in T, it’s copper. At least for standards on the exam]
What is a hub?
aka “Multi-port repeater”
A rather primitive, obsolete networking device that directs data packets to all connected devices, regardless of whether the data is destined for that device. In other words, traffic into one port is repeated to every other port.
A passive hub does nothing but pass along electrical signals, while an active hub regenerates the signal (and might provide some buffering).
A hub operates at what OSI level?
Layer 1 - Physical (Because no forwarding decisions are made internally)
What are the main shortcomings of a hub?
Doesn’t make intelligent forwarding decisions and forwards all data to everyone, which is inefficient.
Only allows half-duplex communication between devices (i.e. one direction at a time). Inefficient and can lead to a lot of collisions, especially as network speeds increase.
Only works at 10 and 100 megabit/s. Doesn’t work with gigabit ethernet.
What is a bridge?
A networking device that connects two local area networks, or connects network segments to form a larger network.
Bridges got around some of the limitations of hubs by intelligently filtering and forwarding traffic between segments based on MAC addresses. This allowed larger networks with more devices, but without the hub’s inefficiencies involving collisions.
Bridges separate collision domains, but not broadcast domains.
Can be used to connect different topologies (e.g. ethernet network to token ring network).
A bridge operates at what OSI level?
Layer 2 - Data Link
Today’s _____ evolved from older-style bridges.
switches
What is a common example of a modern bridge?
Wireless access point (which bridges wired ethernet to wireless ethernet)
What are the key similarities between a bridge and switch?
Both forward traffic based on MAC address.
Both therefore operate at OSI Level 2.
