CCC NET 125 Chapter 4

Unshielded twisted-pair - UTP - cable

A general type of cable, with the cable holding twisted pairs of copper wires and the cable itself having little shielding.

Rollover

A Cisco proprietary cable used to connect a workstation to a router or switch console port.

Hub and Spoke

A WAN version of the star topology in which a central site interconnects branch sites using point-to-point links.

Ethernet Crossover

A cable used to interconnect similar devices. For example to connect a switch to a switch, a host to a host, or a router to a router.

logical topology

A map of the devices on a network representing how the devices communicate with each other.

Frequency modulation - FM

A method of transmission in which the carrier frequency varies in accordance with the signal.

The end-user device needs mobility when connecting to the network.

A network administrator is designing a new network infrastructure that includes both wired and wireless connectivity. Under which situation would a wireless connection be recommended?

wireless access point - WAP

A network device that provides connectivity of wireless clients to connect to a data network.

More expensive usually than copper media over the same distance but for a higher capacity. Different skills and equipment required to terminate and spice the cable infrastructure. More careful handling than copper media.

Advantages of fiber-optic media include: immunity to electromagnetic interference, it will not conduct unwanted electrical currents due to grounding issues, and it has relatively low signal loss over distance. Disadvantages to optical fiber media implementation includes:

Wire map Cable length Signal loss due to attenuation Crosstalk

After installation, a UTP cable tester should be used to test for what parameters?

Contention-based access

All nodes operating in half-duplex compete for the use of the medium, but only one device can send at a time. However, there is a process if more than one device transmits at the same time. Ethernet LANs using hubs and WLANs are examples of this type of access control.

cross-over

An uncommon cable type used to interconnect similar devices, for example, to connect a switch to a switch, a host to a host, or a router to a router.

coaxial cable/coax

Cable consisting of a hollow outer cylindrical conductor that surrounds a single inner wire conductor. Two types are currently used in LANs: 50-ohm cable, which is used for digital signaling, and 75-ohm cable, which is used for analog signaling.

Higher data rates.

Cables in higher categories are designed and constructed to support what?

Multimode fiber-optic

Can help data travel approximately 1.24 miles or 2 km/200m

Single mode fiber-optic

Can travel approximately 62.5 miles or 100 km/100000m

rollover

Cisco proprietary cable to connect to a console port on switch or a router.

network interface card - NIC

Computer hardware, typically used for LANs, that allows the computer to connect to some networking cable. It can then send and receive data over the cable at the direction of the computer.

Multimode fiber - MMF

Consists of a larger core and uses LED emitters to send light pulses. Specifically, light from an LED enters the multimode fiber at different angles. Popular in LANs because they can be powered by low-cost LEDs. It provides bandwidth up to 10 Gb/s over link lengths of up to 550 meters.

false

Consists of a very small core and uses expensive laser technology to send a single ray of light to transmit data is known as multi-mode fiber optic cable.

Token Ring - IEEE 802.5 Fiber distributed Data Interface - FDDI, which is based on the IEEE 802.4 token bus protocol.

Controlled access can be inefficient because a device has to wait for its turn before it can use the medium. List two controlled access examples.

false

Copper cabling is terminated with a RJ-48 connector.

STP

Counters EMI and RFI by using shielding techniques and special connections

Synchronous

Data signals are sent along with a clock signal that occurs at evenly spaced time durations referred to as the bit time.

Asynchronous

Data signals are transmitted without an associated clock signal. The time spacing between data characters or blocks can be of arbitrary duration, meaning that the spacing is not standardized. Therefore, frames require start and stop indicator flags.

A wired device does not need to share its access to the network with other devices. Each wired device has a separate communications channel over its own Ethernet cable.

Does a wired device need to share its access to the network with other devices?

Controlled access

Each node has its own time to use the medium. These deterministic types of networks are inefficient because a device must wait its turn to access the medium. Legacy Token Ring LANs are an example of this type of access control.

IEEE 802.2 IEEE 802.3

Ethernet is the dominant LAN technology. Which IEEE standards define it?

The use of color distinguishes between single-mode and multimode patch cords. A yellow jacket is for single-mode fiber cables and orange or aqua for multimode fiber cables.

Explain how fiber optic cables are color coded.

Selecting the cable type or category most suited to a given networking environment. Designing a cable infrastructure to avoid known and potential sources of interference in the building structure. Using cabling techniques that include the proper handling and termination of the cables.

Explain how the susceptibility of copper cables to electronic noise can be limited.

A wireless device will experience degradation in performance based on its distance to a wireless access point. The further the device is from the access point, the weaker the wireless signal it receives. This can mean less bandwidth or no wireless connection at all.

Explain what happens to a wireless device's signal as it is moved further away from the access point?

At present, in most enterprise environments, optical fiber is primarily used as backbone cabling for high-traffic point-to-point connections between data distribution facilities and for the interconnection of buildings in multi-building campuses.

How do most enterprise environments use optical fiber?

The longer the signal travels, the more it deteriorates.

How does signal attenuation effect transmitted data as it travels through a network?

802.16

IEEE standard for WIMAX wireless broadband

802.11

IEEE standard for WLAN WI-FI

802.15

IEEE standard for WPAN bluetooth 1-10 meters

drop the frame

If a node receives a frame and the calculated CRC - Cyclical Redundancy Check - does not match the CRC in the FCS - Frame Check Sequence, what action will the node take?

Start Frame field

Indicates the beginning of the frame. This field tells other devices on the network segment that a frame is starting to be transmitted on the medium.

electromagnetic interference - EMI

Interference by magnetic signals caused by the flow of electricity. It can cause reduced data integrity and increased error rates on transmission channels. The physics of this process are that electrical current creates magnetic fields, which in turn cause other electrical currents in nearby wires. The induced electrical currents can interfere with proper operation of the other wire.

nonreturn to zero

Line code in which 1s are represented by one significant condition and 0s are represented by another.

Manchester encoding

Line code in which each bit of data is signified by at least one voltage level transition.

Wi-Fi: Standard IEEE 802.11 Bluetooth: Standard IEEE 802.15 WiMAX: Standard IEEE 802.16

List the common data communications standards that apply to wireless media:

802.11a 54 Mbps 802.11b 11 Mbps 802.11g 54 Mbps 802.11n 600 Mbps 802.11ac 1.3 Gbps 802.11ad 7 Gbps

List the maximum speed for each of the following wireless standards.

Preamble Destination Source Type Data Frame Check Sequence

List the names of the Ethernet frame fields:

Flag Address Control Protocol Data Frame Check Sequence

List the names of the PPP frame fields:

true

Multi-Mode fiber optic cable consists of a larger core and uses LED emitters to send light pulses. Specifically, light from an LED enters the multimode fiber at different angles.

true

NIC stands for network interface card and is used to connect devices to wired networks.

false

One network topology identifies how end devices and infrastructure devices such as routers, switches, and wireless access points are interconnected. That is the definition of a logical topology.

sessions

PPP establishes logical connections, called ________, between two nodes.

fiber-optic cable

Physical medium that uses glass or plastic threads to transmit data. It consists of a bundle of these threads, each of which is capable of transmitting data into light waves.

radio frequency interference - RFI

Radio frequencies that create noise that interferes with information being transmitted across unshielded copper cabling.

requests for comments - RFC

Series of documents and memoranda encompassing new research, innovations, and methodologies applicable to Internet technologies. RFCs are a reference for how technologies should work.

physical topology

The arrangement of the nodes in a network and the physical connections between them. This is the representation of how the media is used to connect the devices.

physical media

The cabling and connectors used to interconnect the network devices.

Core

The core is actually the light transmission element at the center of the optical fiber. This core is typically silica or glass. Light pulses travel through the fiber core.

Ethernet Straight-through

The most common type of networking cable. It is commonly used to interconnect a host to a switch and a switch to a router.

STP

The new Ethernet 10GB standard uses this form of copper media.

Carrier sense multiple access with collision avoidance (CSMA/CA)

The end device examines the media for the presence of a data signal. If the media is free, the device sends a notification across the media of its intent to use it. After it receives a clearance to transmit, the device then sends the data. This method is used by 802.11 wireless networking technologies.

Carrier sense multiple access with collision detection (CSMA/CD)

The end device monitors the media for the presence of a data signal. If a data signal is absent and therefore the media is free, the device transmits the data. If signals are then detected that show another device was transmitting at the same time, all devices stop sending and try again later. Traditional forms of Ethernet use this method.

Misalignment

The fiber-optic media are not precisely aligned to one another when joined.

media access control - MAC

The lower of the two sublayers of the IEEE standard for Ethernet. It is also the name of that sublayer - as defined by the IEEE 802.3 subcommittee.

End gap

The media does not completely touch at the splice or connection.

End finish

The media ends are not well polished, or dirt is present at the termination.

The properties of the physical media and the technologies chosen for signaling and detecting network signals.

The practical bandwidth of a network is determined by what combination of factors?

bandwidth

The rated throughput capacity of a given network medium or protocol. it is listed as available or consumed data communication resources expressed in bits/second.

false

There are multiple different types of copper cables of the twisted pair variety. They are known as category 3, category 4, etc. The higher the category number the longer the distance each cable can be from a switch or an end node.

fiber optic cable copper cable wireless

There are three basic forms of network media.

STP cable shield the entire bundle of wires with foil, eliminating virtually all interference - more common. STP cable shields the entire bundle of wires as well as the individual wire pairs, with foil eliminating all interference.

There are two common variations of STP. List and explain both.

Error Detection

These frame fields are used for error detection and are included after the data to form the trailer.

true

This data link sublayer provides data link layer addressing and delimiting of data according to the physical signaling requirements of the medium and the type of data link layer protocol in use. Its name is Media Access Control.

error detection

This field checks if the frame has been damaged during the transfer.

addressing

This field helps to direct the frame toward its destination.

Jacket

Typically a PVC jacket that protects the fiber against abrasion, moisture, and other contaminants. This outer jacket composition can vary depending on the cable usage.

Cancellation: Designers now pair wires in a circuit. When two wires in an electrical circuit are placed close together, their magnetic fields are the exact opposite of each other. Therefore, the two magnetic fields cancel each other and also cancel out any outside EMI and RFI signals. Varying the number of twists per wire pair: To further enhance the cancellation effect of paired circuit wires, designers vary the number of twists of each wire pair in a cable.

UTP cable does not use shielding to counter the effects of EMI and RFI. Explain in detail how cable designers have discovered that they can limit the negative effect of crosstalk.

Wireless and Cable Internet installations

UTP cable has essentially replaced coaxial cable in modern Ethernet installations. Where is coaxial cable still commonly used?

false

UTP cabling provides better network noise protection than STP cabling.

Single mode fiber-optic

Used to connect long-distance telephony and cable TV applications.

Buffer

Used to help shield the core and cladding from damage.

Multimode fiber-optic

Used within a campus network

Single mode fiber-optic

Uses lasers in a single stream as a data light source transmitter.

Multimode fiber-optic

Uses light emitting diodes (LEDs) as a data light source transmitter.

The physical components are the electronic hardware devices, media, and other connectors that transmit and carry the signals to represent the bits

What are physical components?

STP cables use the techniques of shielding to counter EMI and RFI and wire twisting to counter crosstalk.

What are the advantages of using Shielded Twisted-Pair - STP - cabling?

Can transmit signals with less attenuation than copper wires and is completely immune to EFI and RFI.

What are the advantages of using fiber-optic cable over copper wires?

100 Mbps

What are the recommended speeds for Cat 5 cables?

1000 Mbps

What are the recommended speeds for Cat 5e cables?

1000 Mbps up to 10 Gbps, but 10 Gbps is not recommended

What are the recommended speeds for Cat 6 cables?

It accepts Layer 3 packets and packages them into data units called frames. It controls Media Access Control and performs error detection.

What are the two Layer 2 or data link layer basic services?

A physical connection using a cable and a wireless connection using radio waves.

What are two types of physical connections?

To counter the negative effects of EMI and RFI, some types of copper cables are wrapped in metallic shielding and require proper grounding connections.

What can be done to counter the negative effects of EMI and RFI?

Layer 2 protocols specify the encapsulation of a packet into a frame and the techniques for getting the encapsulated packet on and off each medium. The technique used for getting the frame on and off the media is called the media access control method.

What is the media access control method?

It first detects whether the media is carrying a signal. If it is, it means that another device is transmitting. When the device attempting to transmit sees that the media is busy, it will wait and try again after a short time period. If no carrier signal is detected, the device transmits its data.

What is the purpose of Carrier Sense Multiple Access (CSMA)

transmitting bits across the local media

What is the purpose of the OSI physical layer?

CSMA/CA

What method is used to manage contention-based access on a wireless network?

rollover

What type of cable is used to connect a workstation serial port to a Cisco router console port?

Unshielded twisted-pair - UTP - cabling is the most common networking media.

What type of cabling is the most common?

to identify which network layer protocol is being used

Which is a function of the Logical Link Control - LLC - sublayer?

full duplex

Which method of data transfer allows information to be sent and received at the same time?

throughput

___________ is the measure of the transfer of bits across the media over a given period of time.

bandwidth

___________is the capacity of a medium to carry data.

goodput

_______is the measure of usable data transferred over a given period of time.

Strengthening material

Surrounds the buffer, prevents the fiber cable from being stretched when it is being pulled. The material used is often the same material used to produce bulletproof vests.

Coaxial

Terminates with BNC, N type and F type connectors

Pulse-code modulation - PCM

A technique in which an analog signal, such as a voice, is converted into a digital signal by sampling the signal's amplitude and expressing the different amplitudes as a binary number. The sampling rate must be at least twice the highest frequency in the signal.

Amplitude modulation - AM

A transmission technique in which the amplitude of the carrier varies in accordance with the signal.

shielded twisted-pair - STP

A type of network cabling that includes twisted-pair wires, with shielding around each pair of wires, as well as another shield around all wires in the cable.

goodput

Application-level throughput. It is the number of useful bits per unit of time from a certain source address to a certain destination, excluding protocol overhead and excluding retransmitted data packets.

Coaxial

Attaches antennas to wireless devices - can be bundled with fiber-optic cabling for two-way data transmission

Half-duplex communication

Both devices can both transmit and receive on the media but cannot do so simultaneously. Ethernet has established arbitration rules for resolving conflicts arising from instances when more than one station attempts to transmit at the same time.

Full-duplex communication

Both devices can transmit and receive on the media at the same time. The data link layer assumes that the media is available for transmission for both nodes at any time. Therefore, there is no media arbitration necessary in the data link layer.

Single-mode fiber - SMF

Consists of a very small core and uses expensive laser technology to send a single ray of light. Popular in long-distance situations spanning hundreds of kilometers, such as those required in long haul telephony and cable TV applications.

If two devices transmit at the same time, a collision will occur. Both devices will detect the collision on the network. This is done by the NIC comparing data transmitted with data received, or by recognizing the signal amplitude is higher than normal on the media. The data sent by both devices will be corrupted and will need to be resent.

If the CSMA process fails, what happens?

Source and Destination Address fields

Indicates the source and destination nodes on the media.

Type field

Indicates the upper-layer service contained in the frame or the length of the frame.

straight-through

It is commonly used to interconnect a host to a switch and a switch to a router.

Coverage area: Wireless data communication technologies work well in open environments. However, certain construction materials used in buildings and structures, and the local terrain, will limit the effective coverage. Interference: Wireless is susceptible to interference and can be disrupted by such common devices as household cordless phones, some types of fluorescent lights, microwave ovens, and other wireless communications. Security: Wireless communication coverage requires no access to a physical strand of media. Therefore, devices and users, not authorized for access to the network, can gain access to the transmission. Network security is a major component of wireless network administration. Shared medium: WLANs operate in half-duplex, which means only one device can send or receive at a time. The wireless medium is shared amongst all wireless users. The more users needing to access the WLAN simultaneously, results in less bandwidth for each user.

List and explain some of the concerns about using wireless networks:

Unshielded Twisted-Pair - UTP Shielded Twisted-Pair - STP Coaxial

List the three main types of copper media used in networking.

Copper cable, fiber-optic cable, wireless

List the three types of network media commonly used.

Cladding

Made from slightly different chemicals than those used to create the core. It tends to act like a mirror by reflecting light back into the core of the fiber. This keeps light in the core as it travels down the fiber.

UTP

Most common network media

crosstalk

Source of interference that occurs when cables are bundled together for long lengths. The signal from one cable can leak out and enter adjacent cables.

Most often used for phone lines.

Where is Category 3 cable (UTP) commonly used?

Used for backbone cabling applications and interconnecting infrastructure devices.

Where is fiber optic cable used in an Enterprise Networks?

Home Integrated service routers - ISR - offer a switching component with multiple ports, allowing multiple devices to be connected by cable. Many ISRs also include a WAP, which allows wireless devices to connect as well.

Which home device incorporates both types of physical connections?

The TIA/EIA-568 standard describes the wire color codes to pin assignments - pinouts - for Ethernet cables.

Which standard describes the wire color codes to pin assignments - pinouts - for Ethernet cables?

It converts bits into a predefined code in order to provide a predictable pattern to help distinguish data bits from control bits.

Which statement correctly describes frame encoding?

They vary depending on protocols.

Which statement describes a characteristic of the frame header fields of the data link layer?

how the connection between nodes appears to the data link layer how nodes share the media

Which two factors influence the method that is used for media access control?

Because light can only travel in one direction over optical fiber, two fibers are required to support the full duplex operation.

Why are two fibers required to support full duplex operation?

Networks use copper media because it is inexpensive, easy to install and has low resistance to electrical current.

Why do networks use copper media?

Frame Stop

The Frame Stop field is a delimiter that indicates the end of the frame.

logical link control - LLC

The IEEE 802.2 standard that defines the upper sublayer of the Ethernet Layer 2 specifications - and other LAN standards.

throughput

The actual data transfer rate between two computers at some point in time. It is impacted by the slowest-speed link used to send data between the two computers, as well as myriad variables that might change during the course of a day.

frame start

This field identifies the beginning of a frame.

type

This field is used by the LLC to identify the Layer 3 protocol.

Point-to-Point

This is the simplest topology that consists of a permanent link between two endpoints. For this reason, this is a very popular WAN topology.

physical

This layer provides the means to transport the bits that make up a data link layer frame across the network media.

Media Access Control - MAC

This lower sublayer defines the media access processes performed by the hardware. It provides data link layer addressing and access to various network technologies.

Mesh

This topology provides high availability, but requires that every end system be interconnected to every other system. Therefore the administrative and physical costs can be significant. Each link is essentially a point-to-point link to the other node. Variations of this topology include a partial mesh where some but not all of end devices are interconnected.

Logical Link Control - LLC

This upper sublayer communicates with the network layer. It places information in the frame that identifies which network layer protocol is being used for the frame. This information allows multiple Layer 3 protocols, such as IPv4 and IPv6, to utilize the same network interface and media.

LLC

This upper sublayer of the data link layer defines the software processes that provide services to the network layer protocols. It is named the_____________ layer.

true

To offer wireless network capabilities you need have a WAP - wireless access point

To counter the negative effects of crosstalk, some types of copper cables have opposing circuit wire pairs twisted together, which effectively cancels the crosstalk.

What do some types of copper cable do to counter the negative effects of crosstalk?

electronic circuitry, media, connectors

What does the physical layer consists of?

The amount of traffic, the type of traffic, and the latency created by the number of network devices encountered between source and destination.

What factors influence throughput?

Using a crossover or straight-through cable incorrectly between devices may not damage the devices, but connectivity and communication between the devices will not take place.

What happens if a crossover or straight-through cable is incorrectly used between networking devices?

Slower network performance might occur as more wireless devices access the network simultaneously.

What happens to a wireless network as more devices use it simultaneously?

The branch sites are connected to a central site through point-to-point links.

What is a characteristic of a WAN hub-and-spoke topology?

A virtual circuit is a logical connection created within a network between two network devices.

What is a virtual circuit?

It is the capacity of a medium to carry data. Digital bandwidth measures the amount of data that can flow from one place to another in a given amount of time. It is typically measured in kilobits per second (kb/s), megabits per second (Mb/s), or gigabits per second (Gb/s).

What is bandwidth?

Copper media is limited by distance and signal interference.

What is copper media limited by?

Dispersion refers to the spreading out of a light pulse over time. The more dispersion there is, the greater the loss of signal strength.

What is dispersion and how does it affect the signal?

Encoding or line encoding is a method of converting a stream of data bits into a predefined "code". Codes are groupings of bits used to provide a predictable pattern that can be recognized by both the sender and the receiver. In the case of networking, encoding is a pattern of voltage or current used to represent bits: the 0s and 1s.

What is encoding?

Latency refers to the amount of time, to include delays, for data to travel from one given point to another.

What is latency?

The physical layer must generate the electrical, optical or wireless signals that represent the "1" and "0" on the media. The method of representing the bits is called the signaling method.

What is signaling?

Up to 70 meters.

What is the distance range for the 802.11n standard?

An Optical Time Domain Reflectometer (OTDR) can be used to test each fiber-optic cable segment. This device injects a test pulse of light into the cable and measures backscatter and reflection of light detected as a function of time. The OTDR will calculate the approximate distance at which these faults are detected along the length of the cable.

What type of cable tester is recommended to test fiber-optic cables?