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WorksheetsQuiz 02 - Networks and Communication
Total questions: 100
Worksheet time: 2hrs 40mins
A network designer is creating a new protocol for a proprietary system. The protocol changes frequently, but the service it provides to the upper layer remains constant. This design philosophy is most directly aligned with which core principle of layered architecture?
The use of a standardized reference model like OSI.
The decoupling of service from protocol.
The implementation of reliable data transfer.
The minimization of information flow across interfaces.
In the OSI model, the service definition of a layer explicitly describes:
The packet headers used for communication with its peer.
The electrical signals used on the transmission medium.
What the layer does, but not how entities above it access it.
The specific algorithms used for error correction.
Analyzing the TCP/IP model, a key design goal was survivability in the event of subnet hardware loss. This goal most directly influenced the choice of:
A connection-oriented transport layer (TCP).
A connectionless internet layer (IP).
A hierarchical addressing structure.
The use of specific guided media like coaxial cable.
A student argues that the TCP/IP Internet Layer is analogous to the postal system because packets, like letters, may arrive out of order and require sorting at the destination. Which layer in the TCP/IP model is actually responsible for this "sorting" (reassembly) function?
Link Layer
Internet Layer
Transport Layer (TCP)
Application Layer
Evaluating the historical context, the OSI model and its protocols failed to dominate the market for several reasons. Which reason is most attributed to the concept of the "apocalypse of the two elephants"?
The protocols were poorly designed and overly complex.
Political and commercial interests favored TCP/IP.
Its standardization occurred after TCP/IP was already widely deployed.
The initial implementations had poor performance.
When comparing UTP and optical fiber, a project manager must justify the higher cost of fiber for a new campus backbone. Which advantage provides the strongest justification for needing to support future 100 Gbps upgrades over long distances?
Smaller size and lighter weight.
Electromagnetic isolation and security.
Significantly lower attenuation.
Lower cost of installation per meter.
A Category 6A/Class E_A cable is specified for a 10-Gbps Ethernet installation. The standard specifies worst-case performance parameters for a 100m channel. If the actual installation only requires a 50m channel, which parameter improves linearly with the reduced distance?
Near-End Crosstalk (NEXT) Loss
Bandwidth (MHz)
Insertion Loss (Attenuation)
Alien Crosstalk immunity
In a noisy factory environment with many electric motors, a technician is selecting cable for a new 1-Gbps Ethernet link. The link will run near large motors. Which cable type is most resistant to the electromagnetic interference generated by this environment?
Category 5e UTP
Category 6 UTP
Category 6A F/UTP (Screened Twisted Pair)
Fully shielded twisted pair (S/FTP)
On a 100m twisted-pair channel, the transmitted power (P_t) is 100 μW. Due to attenuation, the received signal power (P_r) is 25 μW. Simultaneously, crosstalk from a nearby pair induces a noise power (P_c) of 6.25 μW at the receiver. What is the Attenuation-to-Crosstalk Ratio (ACR)?
6 dB
12 dB
0 dB
18 dB
A graded-index multimode fiber is chosen over a step-index multimode fiber for a LAN application primarily to:
Allow the use of cheaper LED light sources.
Increase the absolute distance the signal can travel.
Reduce the modal dispersion caused by multiple propagation paths.
Enable operation in the 1550 nm window for lower attenuation.
A parabolic reflective antenna with a diameter of 3 meters is operating at 8 GHz. Compared to the same antenna operating at 4 GHz, its gain and beamwidth will be:
Higher gain and narrower beamwidth.
Higher gain and wider beamwidth.
Lower gain and narrower beamwidth.
Lower gain and wider beamwidth.
The primary technical reason terrestrial microwave towers require line-of-sight and are placed at great heights is:
To avoid interference from other radio sources.
To overcome the curvature of the Earth and extend the radio horizon.
To ensure the signal is not refracted into the sky.
To increase the transmission power legally allowed.
A geostationary communication satellite must be placed at an altitude of 35,863 km above the equator. This is primarily to ensure:
The satellite is beyond the Earth's atmosphere to avoid attenuation.
The satellite's orbital period matches the Earth's rotation period, making it stationary relative to the ground.
The satellite is in a low-Earth orbit for minimal propagation delay.
The uplink and downlink frequencies do not interfere with each other.
A significant impairment for broadcast radio waves in the 30 MHz to 1 GHz range (VHF/UHF) that is less of a concern for higher frequency microwave signals is:
Atmospheric absorption due to oxygen and water vapor.
Attenuation due to rainfall.
Multipath interference caused by reflections.
The need for strict governmental frequency allocation.
The effective radio line of sight to the horizon is greater than the optical line of sight because:
Radio waves travel in perfectly straight lines.
Radio waves are reflected by the ionosphere.
Radio waves are refracted by the atmosphere, bending slightly toward the Earth.
Radio receivers are more sensitive than the human eye.
In a traditional bus topology LAN using CSMA/CD, the purpose of the binary exponential backoff algorithm after a collision is to:
Assign a deterministic transmission time to each station.
Ensure that a fast sender cannot swamp a slow receiver.
Randomize the retransmission time of colliding stations to reduce the probability of a repeat collision.
Prioritize stations that have been waiting the longest to transmit.
The 1-persistent CSMA/CD protocol used in Ethernet can be considered "greedy." However, it remains stable under high load primarily because of:
The use of a token-passing mechanism during congestion.
The carrier extension and frame bursting features.
The binary exponential backoff algorithm following collisions.
The small frame size mandated by the standard.
The Start Frame Delimiter (SFD) in an IEEE 802.3 frame is primarily used to:
Provide bit synchronization for the receiver.
Indicate the actual start of the frame and enable byte alignment.
Specify the priority level of the frame for quality of service.
Delimit the end of the preamble and the start of the address fields.
A network analyzer captures an Ethernet frame with a Length/Type field value of 0x0800. This most likely indicates:
The frame is an 802.1Q tagged frame.
The MAC Client Data field contains an IPv4 packet.
The frame is a legacy Novell IPX frame.
The length of the data field is 2048 bytes.
Fast Ethernet (100BASE-TX) uses 4B/5B encoding followed by MLT-3 signaling. The primary purpose of the MLT-3 step is to:
Increase the data rate from 100 Mbps to 125 Mbps.
Concentrate the signal energy at lower frequencies to reduce radiated emissions.
Provide synchronization by guaranteeing frequent transitions.
Convert the electrical signal into an optical signal for transmission.
The key advantage of full-duplex operation in switched Ethernet is that it:
Allows the use of lower-quality cabling like Category 3.
Effectively doubles the potential bandwidth between two nodes.
Eliminates the need for a CSMA/CD algorithm.
Both B and C.
Gigabit Ethernet over copper (1000BASE-T) uses four pairs of Category 5 cable, transmitting and receiving on all pairs simultaneously. This technique is necessary to:
Achieve the 1 Gbps data rate without requiring a prohibitively high signaling rate on each pair.
Provide redundancy in case one pair fails.
Allow for longer cable runs than 100BASE-TX.
Simplify the encoding scheme to simple NRZ.
10-Gbps Ethernet is considered a compelling alternative to ATM for MAN and WAN applications primarily because:
It offers a much higher data rate than ATM.
It eliminates expensive conversion between Ethernet frames and ATM cells.
It provides superior quality of service guarantees for voice and video.
It uses cheaper coaxial cable instead of fiber optics.
The 100-Gbps Ethernet standard (802.3ba) uses a multilane distribution technique. The primary reason for distributing data across multiple 'virtual lanes' is to:
Provide redundancy and error correction across the lanes.
Simplify the design of the Physical Medium Attachment (PMA) sublayer by allowing it to operate at a lower per-lane rate.
Allow different lanes to take different physical paths through the network.
Enable the use of existing 10-Gbps components without modification.
In an IEEE 802.1Q VLAN tagged frame, the VLAN Identifier (VID) is 12 bits long. The maximum number of possible VLAN configurations in a network is:
4096
4094
4095
8192
The Canonical Format Indicator (CFI) bit in an 802.1Q tag is primarily used for:
Indicating the priority level of the frame.
Compatibility between Ethernet and Token Ring networks.
Identifying the specific VLAN the frame belongs to.
Preventing forwarding loops in a switched network.
The 8B/10B encoding scheme used in Fibre Channel and Gigabit Ethernet incorporates 'disparity control.' The main purpose of this is to:
Correct single-bit errors in the transmitted code group.
Ensure the encoded stream is DC balanced and has a high transition density.
Scramble the data to appear random for security purposes.
Compress the data to reduce the overhead from 25% to 3%.
Comparing the 4B/5B (100 Mbps) and 64B/66B (10/100 Gbps) encoding schemes, a key advantage of 64B/66B is its:
Built-in error correction capability.
Lower overhead (3% vs. 25%).
Simpler encoding and decoding logic.
Ability to use ternary signaling instead of binary.
The primary purpose of a scrambler in a physical layer transmission system is to:
Encrypt the data for security.
Eliminate long strings of consecutive zeros or ones to aid clock recovery and spectral shaping.
Add redundancy for forward error correction.
Convert binary data into a ternary signal.
When evaluating the OSI model's contribution, its most enduring impact on network design is considered to be:
Its seven-layer structure, which is implemented in modern networks.
Its specific protocol specifications for each layer.
Its explicit distinction between services, interfaces, and protocols.
Its requirement for internationally standardized protocols.
A programmer is designing an application that uses a network service. The service definition, from the programmer's perspective, is most analogous to:
The source code of the protocol's implementation.
The abstract data type or object defining available operations.
The physical layout of the network interface card.
The specific packet format used on the wire.
The TCP/IP Link Layer is described as an 'interface' rather than a true layer. This is best explained by its primary function, which is to:
Route packets between different networks.
Provide end-to-end reliable data delivery.
Describe how hosts interface with specific transmission links like Ethernet.
Translate between different application protocols.
The Internet Layer (IP) is considered the 'linchpin' of the TCP/IP architecture because it:
Provides reliable, in-order delivery of data.
Shields higher layers from the underlying network technologies.
Is the only layer that performs encryption for security.
Is implemented identically on every operating system.
A network engineer must choose a transport protocol for a new video streaming application where low latency is more critical than perfect reliability. The most appropriate choice from the TCP/IP suite is:
TCP, because it ensures all video frames arrive correctly.
IP, because it is the simplest and fastest protocol.
ICMP, because it handles control messages efficiently.
UDP, because it lacks sequencing and retransmission overhead.
The decision to omit official session and presentation layers from the TCP/IP model is justified by the argument that:
These functions are never needed in a real-world network.
These functions can be embedded within application protocols as needed.
The OSI model's layers are a proprietary standard.
The Link Layer can perform all necessary presentation tasks.
A key design factor that limits the data rate and distance for both guided and unguided media is:
The color of the cable jacket or antenna.
The brand of the network interface card.
Transmission impairments like attenuation.
The version of the operating system used.
For unguided media, the signal's bandwidth and directionality are more important than the medium itself because:
The atmosphere has a fixed and unchangeable bandwidth.
The signal's properties determine how it interacts with the transmission environment.
Guided media are always superior for high-bandwidth applications.
Governments regulate only the medium, not the signal.
Alien crosstalk is a significant concern in modern cabling systems because:
It is caused by signals from other planets.
It refers to interference from cables in adjacent conduits, which is hard to mitigate.
It only occurs in coaxial cable installations.
It is a type of error that encryption protocols introduce.
The significant 'shoulder' in the attenuation vs. frequency graph for twisted-pair cable (around 1-10 MHz) is primarily caused by:
Impedance mismatches and return loss.
The skin effect, which increases resistance at higher frequencies.
Crosstalk from adjacent pairs in the same cable.
Atmospheric absorption of radio waves.
A Category 7/Class F cable uses S/FTP construction (individually shielded pairs + overall shield). The main advantage this provides over UTP for supporting 10-Gbps Ethernet and beyond is:
A significant reduction in both internal pair-to-pair crosstalk and external alien crosstalk.
A much smaller physical diameter, allowing for easier installation.
The ability to use cheaper plastic connectors.
Lower attenuation at very low frequencies (below 1 MHz).
The parameter 'Insertion Loss' for a twisted-pair channel fundamentally represents:
The amount of signal power coupled from a nearby transmitter.
The signal attenuation from the transmitter to the receiver.
The loss of data packets due to buffer overflows in a switch.
The impedance of the connector pins.
Near-End Crosstalk (NEXT) loss is measured at the same end of the link as the transmitter. This is because:
The transmitted signal is strongest at the near end, making the crosstalk problem most severe there.
Measuring at the far end would require more expensive equipment.
Far-end crosstalk is canceled out by the twisting of the pairs.
The standard defines loss only in one direction.
For a successful transmission on a twisted-pair link, the condition that must be met is:
The received signal power (P_r) must be less than the crosstalk power (P_c).
The Attenuation-to-Crosstalk Ratio (ACR) must be negative.
The received signal power (P_r) must be greater than the crosstalk power (P_c).
The Near-End Crosstalk (NEXT) loss must be less than the insertion loss.
The primary reason coaxial cable can support higher frequencies and data rates than twisted pair is its:
Use of optical light instead of electrical signals.
Shielded, concentric construction which better contains the signal and rejects interference.
Larger overall diameter, which always means better performance.
Inability to support analog signals, eliminating noise.
A key application where coaxial cable remains dominant over fiber optics is in:
Long-haul telecommunications trunks between countries.
'Cable TV' distribution from a provider to individual homes.
High-speed backbone links within corporate data centers.
Undersea communication cables.
The core of an optical fiber is surrounded by cladding with a lower refractive index. This is essential for the principle of:
Electromagnetic isolation.
Total internal reflection.
Amplitude modulation.
Frequency division multiplexing.
The single most significant advantage of optical fiber that drove its adoption in long-haul telephone networks is:
Its small size and light weight.
Its immunity to electromagnetic interference.
Its immense bandwidth and much longer distances between repeaters.
Its lower cost per meter compared to copper coaxial cable.
A "light-emitting diode (LED)" source is often chosen over an "injection laser diode (ILD)" for fiber optic systems in LANs because LEDs are:
More efficient and can sustain higher data rates.
Less costly, operate over a greater temperature range, and have a longer life.
Capable of producing a more coherent and focused light beam.
Required for use with single-mode fiber.
The 1550 nm transmission window is preferred for long-distance and high-capacity (WDM) fiber optic systems primarily because:
It is the wavelength of visible red light, making alignment easier.
It corresponds to the lowest attenuation region in silica-based fibers.
LEDs are cheapest to manufacture at this wavelength.
It is the only wavelength that can be used with multimode fiber.
Scattering in optical fibers, which contributes to attenuation, is caused by:
The magnetic field of the Earth.
Light rays changing direction after striking impurities or small particles in the glass.
The conversion of light energy directly into heat.
The absorption of specific wavelengths by the plastic buffer coating.
The term "microwave frequencies" typically refers to the range of approximately 1 GHz to 40 GHz. A key characteristic of signals in this range is:
They are omnidirectional and cannot be focused.
They can form highly directional beams, making them suitable for point-to-point links.
They are completely unaffected by rain or atmosphere.
They are used exclusively for broadcast radio and television.
The loss for a wireless signal in free space means loss increases with the square of the distance. In contrast, for guided media like fiber, loss:
Also increases with the square of the distance.
Is constant regardless of distance.
Increases linearly with distance (a linear function in dB).
Decreases exponentially with distance.
A major design constraint for satellite systems operating above 10 GHz is:
Increased signal attenuation due to rainfall and atmospheric absorption.
The inability to focus the signal into a narrow beam.
The requirement for satellites to be in low-Earth orbit.
The lack of available transmitter power.
The 4/6-GHz band for satellite communications (e.g., 5.925-6.425 GHz uplink, 3.7-4.2 GHz downlink) uses different frequencies for uplink and downlink to:
Make the satellite electronics more complex and expensive.
Allow the use of smaller antennas on the ground.
Prevent the satellite's powerful transmitted signal from interfering with its own weak received signal.
Comply with international law that mandates higher frequencies for space-to-Earth transmission.
A significant and unavoidable impairment in geostationary satellite communication is the:
Inability to support data rates above 1 Mbps.
High cost of launching the satellites.
Approximately quarter-second propagation delay for a round trip.
Eavesdropping risk because the signal is broadcast to everyone.
A Very Small Aperture Terminal (VSAT) system is economically attractive for businesses because it:
Uses large, expensive antennas at each subscriber station.
Allows many low-cost subscriber stations to share satellite transmission capacity via a hub station.
Operates in the 20/30-GHz band, which has no attenuation.
Does not require a central hub station for coordination.
The Global Positioning System (GPS) requires a receiver to get signals from at least four satellites because:
This provides redundancy in case one satellite fails.
Three distances are needed to calculate latitude, longitude, and height, and a fourth is needed to synchronize the receiver's cheap clock with the satellites' atomic clocks.
The signals from three satellites are too weak to be detected.
Government regulations require a minimum of four for accuracy.
Broadcast radio (e.g., FM radio, VHF/UHF TV) is omnidirectional, unlike microwave. This characteristic is a result of:
The use of dish-shaped antennas for broadcasting.
The lower frequencies used, which make it difficult to focus the energy into a narrow beam.
Regulations that prohibit directional broadcasting.
The use of digital instead of analog signaling.
Multipath interference is a particular problem for broadcast radio because:
The signals are always too weak.
Reflected waves can arrive at the receiver out of phase with the direct path signal, causing cancellation or distortion.
The transmitters are not powerful enough.
The atmosphere absorbs the signal at these frequencies.
Infrared wireless transmission is generally limited to "confined areas" like a single room because:
Its signals are easily absorbed by walls and other obstacles.
It requires a federal license to operate over longer distances.
It uses frequencies that are allocated only for short-range use.
The transmitters have a maximum power of 1 milliwatt by law.
An isotropic antenna is a theoretical construct that radiates power equally in all directions. It is used primarily as:
A practical antenna for handheld radios.
A reference point for calculating the gain and directionality of real antennas.
The antenna type used in all satellite dishes.
An antenna with negative gain.
The property of a parabola that makes it ideal for microwave antennas is that:
It is the strongest geometric shape for supporting heavy equipment.
All waves emanating from the focus are reflected parallel to the axis, creating a focused beam.
It can be manufactured more cheaply than other shapes.
It naturally filters out interference from other frequencies.
Antenna gain is achieved by:
Amplifying the input signal to get more output power.
Focusing radiated power in desired directions at the expense of radiation in other directions.
Using a larger power supply than the input requires.
Receiving signals from multiple directions simultaneously.
Ground wave propagation is most effective at frequencies below 2 MHz because:
The waves are refracted by the ionosphere at these frequencies.
The long wavelengths can diffract around the curvature of the Earth and induce currents in the ground.
There is no atmospheric noise at these low frequencies.
The waves travel in perfectly straight lines.
Sky wave propagation (2-30 MHz) relies on the ionosphere to:
Absorb the signal completely for security.
Reflect (refract) signals back to Earth, enabling long-distance communication.
Focus the signal into a narrow beam for point-to-point links.
Convert the signal from analog to digital.
For line-of-sight (LOS) propagation above 30 MHz, the radio horizon is effectively about 4/3 times the geometric optical horizon. This extension is due to:
Diffraction of the waves around obstacles.
Atmospheric refraction that bends radio waves slightly toward the Earth.
Reflection of the waves from a layer of the atmosphere.
The use of higher-gain antennas.
If a transmitting antenna is 100 m high, the distance to the radio horizon (using K=4/3) is approximately:
41 km
3.57 km
35.7 km
14.1 km
In a bus topology LAN, the purpose of the terminator at each end of the bus is to:
Amplify the signal to extend the network's length.
Prevent reflections by absorbing the signal at the end of the medium.
Assign unique addresses to each station on the network.
Convert the signal from digital to analog.
Carrier Sense Multiple Access (CSMA) protocols are effective because they:
Eliminate collisions entirely.
Allow stations to detect if the medium is already in use before transmitting, thus reducing the probability of collision.
Guarantee each station a fixed time slot for transmission.
Use a dedicated control channel for scheduling transmissions.
The "persistence" algorithm in CSMA that is most likely to cause a collision immediately after a transmission ends is:
Nonpersistent CSMA
1-Persistent CSMA
p-Persistent CSMA (with a small p)
Slotted ALOHA
The minimum frame length requirement in traditional Ethernet is directly related to:
The maximum number of stations allowed on the network.
The minimum size of an IP packet.
The maximum cable length and the speed of signal propagation, ensuring a station can detect a collision before it stops transmitting.
The addressing scheme used in the frame header.
Binary exponential backoff contributes to the stability of Ethernet under high load by:
Assigning a fixed, deterministic retransmission time to each station.
Progressively increasing the mean random delay before retransmission after repeated collisions.
Giving priority to stations that have experienced the most collisions.
Shutting down stations that cause too many collisions.
In a twisted-pair star topology with a hub, collision detection is based on logic, not voltage levels, because:
The hub can detect activity on more than one input port and generate a collision presence signal.
The signals on twisted pair are too weak to measure voltage magnitude accurately.
The terminator absorbs the signal, preventing voltage measurements.
The encoding scheme (like Manchester) does not allow for voltage swings.
The Q-tagged frame in IEEE 802.3 is used to:
Indicate a high-priority frame for quality of service.
Support IEEE 802.1Q VLAN functionality by inserting a tag into the frame.
Encrypt the payload of the frame for security.
Delimit the start of a streaming data sequence.
The Extension field in a Gigabit Ethernet half-duplex frame exists to:
Carry additional user data beyond the 1500-byte limit.
Ensure the carrier event duration is long enough for collision detection on a 1 Gbps half-duplex link.
Provide space for the VLAN tag information.
Indicate the type of protocol in the MAC client data field.
10BASE5, 10BASE2, and 10BASE-T all share the same:
Type of coaxial cable.
Physical bus topology
Data rate (10 Mbps) and MAC protocol.
Maximum segment length of 500 meters.
The primary technological innovation that allowed Fast Ethernet (100BASE-T) to achieve 100 Mbps over twisted pair was:
The invention of a new type of copper wire.
The use of more efficient signal encoding schemes (like 4B/5B and MLT-3) instead of Manchester.
A radical change to the CSMA/CD algorithm.
The elimination of the frame check sequence for speed.
100BASE-T4 was developed specifically to:
Provide the highest performance for new installations.
Allow 100 Mbps operation over voice-grade Category 3 cable by using four pairs.
Enable longer distances than 100BASE-TX.
Simplify the transceiver design by using only two pairs.
The transition from shared hubs to switched hubs was crucial for enabling full-duplex Ethernet because switches:
Operate in the infrared spectrum, avoiding collisions.
Create a separate collision domain for each port, eliminating the possibility of collisions on point-to-point links.
Use a token-passing mechanism on the backbone.
Implement a proprietary version of the CSMA/CD algorithm.
Carrier extension in Gigabit Ethernet (for half-duplex operation) addresses the problem of:
Stations being too greedy and not backing off.
The minimum frame size being too short relative to the increased network speed and size, by extending short frames.
The maximum frame size being too small for modern applications.
Attenuation on long fiber optic cables.
Frame bursting in Gigabit Ethernet improves efficiency by:
Allowing a station to send a burst of small frames without relinquishing control between them.
Breaking large frames into smaller fragments for transmission.
Using a higher burst clock speed for the first part of a transmission.
Sending frames in both directions on the wire simultaneously.
1000BASE-LX supports longer distances than 1000BASE-SX primarily because it uses:
A longer wavelength of light (1300 nm vs. 850 nm) which has lower attenuation in fiber.
A higher power laser that consumes more electricity.
A special type of plastic fiber instead of glass.
A simpler encoding scheme that is less susceptible to noise.
The driving requirement for the development of 10-Gigabit Ethernet was the:
Need for a cheaper alternative to 100BASE-TX.
Explosive growth of Internet and intranet traffic demanding higher backbone capacity.
Desire to replace ATM in all desktop computer connections.
Invention of a new type of fiber optic cable.
A key difference between 10-Gigabit Ethernet and its predecessors is that it:
Only operates in full-duplex mode, making the CSMA/CD protocol obsolete for this speed.
Uses a modified version of the CSMA/CD protocol with longer slot times.
Is only defined for operation over copper twisted-pair cabling.
Abandons the familiar IEEE 802.3 frame format
The market driver most likely to be an early adopter of 100-Gigabit Ethernet is a(n):
Small enterprise office with 50 users.
Internet exchange or ISP core network handling massive traffic flows.
Home user with a cable modem.
University computer lab.
The IEEE 802.3ba task force developed both 40 Gbps and 100 Gbps standards because:
40 Gbps was the maximum possible speed on copper.
Aggregate network core requirements and individual server requirements were increasing at different rates.
They could not agree on a single standard.
100 Gbps technology was not technically feasible at the time.
The primary purpose of the IEEE 802.1Q standard is to:
Allow the creation of virtual LANs (VLANs) across a switched infrastructure.
Define a new physical layer for faster Ethernet.
Specify a wireless LAN protocol.
Encrypt data at the data link layer.
The state transition rules for MLT-3 encoding ensure that a transition occurs on every:
Clock cycle.
Binary 1 in the input stream.
Binary 0 in the input stream.
Change in voltage level.
In the 64B/66B scheme, the sync header (01 or 10) is used by the receiver primarily to:
Encrypt the payload.
Achieve block alignment and synchronization.
Identify the type of VLAN.
Determine the length of the frame.
The descrambler successfully recovers the original data because it:
Uses a secret key to decrypt the signal.
Applies the inverse of the scrambling function to the received bit stream.
Drops any frames that contain scrambled bits.
Relies on the Frame Check Sequence (FCS) for correction.
When comparing the OSI and TCP/IP models, a key practical difference is that in TCP/IP:
The session and presentation layers are well-defined and mandatory.
The network interface layer is standardized across all implementations.
The application layer encompasses the functions of the OSI session, presentation, and application layers.
The transport layer only offers a connectionless service.
A network architect chooses to use single-mode fiber instead of multimode fiber for a new 500-meter backbone link. The most compelling technical reason for this choice is that single-mode fiber:
Is cheaper per meter than multimode fiber.
Uses cheaper LED transmitters.
Has a higher core diameter, making connections easier.
Has much lower modal dispersion, supporting higher data rates over longer distances.
A systems administrator notices poor performance on a 100-meter Category 5e link. A cable tester shows high attenuation and poor NEXT performance at 100 MHz. The most likely cause is:
The use of 100BASE-TX instead of 100BASE-T4.
A faulty connector or cable that does not meet Category 5e specifications.
The absence of a VPN on the link.
The use of TCP instead of UDP.
When designing a wireless link between two buildings 15 km apart, the factor that is most critical to calculate first is:
The cost of the antennas.
Whether the radio line of sight is clear, considering the curvature of the Earth and antenna heights.
the brand of the wireless equipment.
The encryption protocol to be used.
A company wants to implement a VLAN to isolate the traffic of its finance department from the rest of the network. The key mechanism that makes this possible is that switches:
Block all IP traffic between subnets by default.
Use the 802.1Q tag to identify and restrict broadcast traffic to ports assigned to the same VLAN.
Physically separate the cables for different departments.
Reduce the data rate for the finance department's VLAN.
The evolution of Ethernet from 10 Mbps to 100 Gbps, while maintaining backward compatibility with the MAC frame format, is a major reason for its success. This is because it:
Forces users to upgrade all equipment simultaneously.
Guarantees that all versions have the same latency and jitter characteristics.
Means that all physical cabling can be reused when upgrading speeds.
Protects investments in existing network management software, applications, and skills.
In the context of the TCP/IP model, the functionality of the OSI Data Link Layer is primarily split across which two TCP/IP layers?
Application and Transport
Internet and Transport
Network Interface and Internet
Physical and Network Interface
The term "seamless way" in the design goal of the TCP/IP model refers to the ability to:
Hide the underlying network technologies from the applications and users.
Provide perfectly reliable data delivery without any errors.
Encrypt all traffic between different networks.
Use the same physical medium for all interconnected networks.
Evaluating the OSI model's principle of minimizing information flow across interfaces, this leads to layer boundaries that are placed:
Where the service provided is simple and the interaction between layers is minimal.
Where the most complex processing occurs.
At the exact midpoint of the seven-layer stack.
Based on the political needs of the standardizing organizations.
A "star" physical topology, as used in 10BASE-T and later Ethernet standards, simplifies fault isolation because:
A failure of the central hub brings down the entire network, making the problem obvious.
A failure in one cable or device typically affects only the single connected device, not the entire network.
It uses a logical bus, so all faults are broadcast to all stations.
It requires more cable than a bus, providing redundancy.
