Q: Data services delivered to a television screen, obtained either via a broadcast TV aerial or through telephone lines, are collectively known by what general term?

Introduction / Context: In the pre-web era, consumers accessed textual and simple graphical information services on television sets. Some systems were broadcast one-way over TV carriers; others were interactive over telephone lines with a set-top unit or adapter. This question asks for the umbrella term that covers both models when the output is presented on a TV screen. Given Data / Assumptions: Data may arrive via a TV aerial (broadcast) or telephone line (dial-up/interactive). Display device is a television set. We seek the generic category name spanning these delivery modes. Concept / Approach: Videotex is the broad category for interactive or broadcast information services designed for display on TV sets. It encompasses Teletext (one-way broadcast pages embedded in TV signals) and Viewdata (interactive, dial-up services such as Prestel). Telesoftware referred to software distributed via broadcast data channels, a niche subset. Therefore, the most general term that fits both reception paths is Videotex. Step-by-Step Solution: Identify two delivery paths: broadcast and dial-up.Map specific examples to the umbrella: Teletext (broadcast) and Viewdata (dial-up) fall under Videotex.Select the general category term: Videotex. Verification / Alternative check: Historical documentation describes Teletext and Viewdata as variants within the broader Videotex family, which targeted mass-market TV displays with simple navigation and limited color/graphics. Why Other Options Are Wrong: Viewdata: interactive telephone-line variant only. Teletext: broadcast pages only; not interactive over phone lines. Telesoftware: specialized broadcast of software, not the general service class. None of the above: incorrect because Videotex is correct. Common Pitfalls: Treating Teletext as synonymous with all TV-based data services; forgetting that Viewdata required a modem and could be navigated interactively. Final Answer: Videotex.

Q: On Windows NT and related Windows clients, which command-line utility should you use to view whether IP configuration (address, mask, gateway, DNS) has been assigned to the system?

Introduction / Context: Verifying a machine's IP address, subnet mask, default gateway, and DNS servers is a common troubleshooting step. Windows platforms provide several network utilities, but only a few display full IP configuration in a concise, reliable way from the command line. This question tests which tool is appropriate on Windows NT and later Windows systems. Given Data / Assumptions: Platform: Windows NT class systems. Need: display assigned IP configuration. Prefer a command-line utility for scripting and remote use. Concept / Approach: IPCONFIG outputs the current TCP/IP configuration, including DHCP details and DNS suffixes. Adding the /all switch provides complete information, including MAC addresses and lease data. NETSTAT lists active connections, ports, and routing tables; NBTSTAT shows NetBIOS over TCP/IP name tables; WINIPCFG existed on Windows 9x (GUI), not on NT-class systems; PING tests reachability but does not show local configuration. Step-by-Step Solution: State requirement: view local IP configuration parameters.Map to tool: IPCONFIG or IPCONFIG /ALL provides exactly that.Eliminate tools meant for connections, NetBIOS, GUI-only on 9x, or reachability tests.Select IPCONFIG. Verification / Alternative check: Windows documentation and help text (ipconfig /?) confirm this usage. Modern equivalents persist across Windows versions, making IPCONFIG the canonical choice. Why Other Options Are Wrong: NBTSTAT: NetBIOS name tables, not IP config. NETSTAT: sockets and routes, not assigned addresses. WINIPCFG: Windows 9x GUI utility, not NT. PING: reachability test, not configuration display. Common Pitfalls: Confusing netstat -r (route table) with IP address assignment; expecting ping to reveal local addresses; using winipcfg on NT where it is unavailable. Final Answer: IPCONFIG.

Question 1

In single-mode optical fiber design, the core diameter is approximately what multiple of the optical wavelength carried in the fiber?

Accepted Answer

Introduction / Context: Single-mode fibers guide only the fundamental mode by using a small core diameter relative to the operating wavelength. Understanding the approximate relationship between core size and wavelength helps explain why single-mode fibers use cores near 8–10 micrometres for common telecom wavelengths around 1.3–1.55 micrometres. This question asks for the appropriate order-of-magnitude multiple. Given Data / Assumptions: Telecom wavelengths: roughly 1.3 μm or 1.55 μm. Typical single-mode core diameters: roughly 8–10 μm (mode field diameter ~9–10.5 μm). We want an approximate multiple, not an exact formula. Concept / Approach: The V-number (normalized frequency) criterion governs single-mode operation: V = (2 * pi * a / λ) * NA, and single-mode occurs when V < 2.405. For typical refractive index profiles and numerical apertures used in telecom fibers, achieving V near the cutoff yields core radii a that correspond to core diameters on the order of ~8–10 μm at 1.3–1.55 μm wavelengths—roughly 6–10 times the wavelength. Therefore, “about 10 times the wavelength” is a reasonable, rounded statement that matches industry practice. Step-by-Step Solution: Recall telecom λ ≈ 1.3–1.55 μm; single-mode core diameter ≈ 8–10 μm.Compute rough multiple: 8–10 μm / 1.3–1.55 μm ≈ 6–8.Choose the closest rounded description: about 10× wavelength (order-of-magnitude match).Discard clearly wrong multiples like 3× or statements about “fiber radius.” Verification / Alternative check: ITU-T G.652 single-mode fibers list mode field diameters near 9–10.5 μm at 1.31 μm and 1.55 μm, reinforcing the “roughly ten times” characterization in common teaching texts. Why Other Options Are Wrong: 10× fiber radius: nonsensical; radius vs diameter mismatch. 7 times the light: grammatically incorrect and imprecise. 3× wavelength: far too small for standard single-mode telecom fiber cores. None of the above: invalid because an acceptable approximation is provided. Common Pitfalls: Treating the multiple as exact rather than an order-of-magnitude rule; confusing core diameter with cladding diameter (usually 125 μm for standard fibers). Final Answer: About 10 times the wavelength of the light carried in the fiber.

Question 2

In a synchronous modem transmit chain, the digital-to-analog converter (DAC) outputs the analog waveform that is next shaped and conditioned by which stage before entering the line interface?

Accepted Answer

Introduction / Context: Synchronous modems convert digital symbols into an analog passband waveform suitable for transmission over band-limited channels (e.g., telephone circuits). The transmit signal path includes modulation, digital signal processing, digital-to-analog conversion, shaping, and line driving. This question focuses on the immediate analog-domain stage that conditions the DAC's output before the signal is launched onto the channel. Given Data / Assumptions: We are discussing the transmit chain of a synchronous modem. The DAC has just produced an analog representation of the modulated signal. The channel exhibits frequency-selective characteristics requiring spectral shaping/compensation. Concept / Approach: After symbol mapping (modulation) and digital pulse shaping, the DAC outputs an analog waveform. Before handing the signal to the hybrid/line interface, the transmitter applies analog filtering and pre-emphasis to comply with spectral masks and partially counteract channel distortion. This block is commonly referred to as the transmit equalizer (or line-shaping filter). The equalizer helps control intersymbol interference and match the channel's amplitude/phase response. The modulator logically precedes the DAC in most modern architectures; the demodulator is a receive-side component; the terminal is the DTE, not a modem stage. Step-by-Step Solution: Place blocks in order: mapping/filtering → DAC → analog shaping/equalization → hybrid/line driver.Identify the analog block following DAC: the transmit equalizer.Eliminate receive-side and non-modem elements.Select “Equalizer.” Verification / Alternative check: Practical modem and xDSL transmitters include analog reconstruction filters and pre-emphasis/equalization after the DAC to meet spectral masks and mitigate channel roll-off, confirming the stage selection. Why Other Options Are Wrong: Modulator: functionally upstream of the DAC in typical digital implementations. Demodulator: receive-side only. Terminal: external DTE device, not a modem stage. None of the above: incorrect because a transmit equalizer is standard. Common Pitfalls: Assuming the DAC directly feeds the line without analog reconstruction/equalization; confusing transmit versus receive equalizers; overlooking that block diagrams may aggregate shaping under “equalizer/filters.” Final Answer: Equalizer.

Question 3

Data services delivered to a television screen, obtained either via a broadcast TV aerial or through telephone lines, are collectively known by what general term?

Accepted Answer

Introduction / Context: In the pre-web era, consumers accessed textual and simple graphical information services on television sets. Some systems were broadcast one-way over TV carriers; others were interactive over telephone lines with a set-top unit or adapter. This question asks for the umbrella term that covers both models when the output is presented on a TV screen. Given Data / Assumptions: Data may arrive via a TV aerial (broadcast) or telephone line (dial-up/interactive). Display device is a television set. We seek the generic category name spanning these delivery modes. Concept / Approach: Videotex is the broad category for interactive or broadcast information services designed for display on TV sets. It encompasses Teletext (one-way broadcast pages embedded in TV signals) and Viewdata (interactive, dial-up services such as Prestel). Telesoftware referred to software distributed via broadcast data channels, a niche subset. Therefore, the most general term that fits both reception paths is Videotex. Step-by-Step Solution: Identify two delivery paths: broadcast and dial-up.Map specific examples to the umbrella: Teletext (broadcast) and Viewdata (dial-up) fall under Videotex.Select the general category term: Videotex. Verification / Alternative check: Historical documentation describes Teletext and Viewdata as variants within the broader Videotex family, which targeted mass-market TV displays with simple navigation and limited color/graphics. Why Other Options Are Wrong: Viewdata: interactive telephone-line variant only. Teletext: broadcast pages only; not interactive over phone lines. Telesoftware: specialized broadcast of software, not the general service class. None of the above: incorrect because Videotex is correct. Common Pitfalls: Treating Teletext as synonymous with all TV-based data services; forgetting that Viewdata required a modem and could be navigated interactively. Final Answer: Videotex.

Question 4

On Windows NT and related Windows clients, which command-line utility should you use to view whether IP configuration (address, mask, gateway, DNS) has been assigned to the system?

Accepted Answer

Introduction / Context: Verifying a machine's IP address, subnet mask, default gateway, and DNS servers is a common troubleshooting step. Windows platforms provide several network utilities, but only a few display full IP configuration in a concise, reliable way from the command line. This question tests which tool is appropriate on Windows NT and later Windows systems. Given Data / Assumptions: Platform: Windows NT class systems. Need: display assigned IP configuration. Prefer a command-line utility for scripting and remote use. Concept / Approach: IPCONFIG outputs the current TCP/IP configuration, including DHCP details and DNS suffixes. Adding the /all switch provides complete information, including MAC addresses and lease data. NETSTAT lists active connections, ports, and routing tables; NBTSTAT shows NetBIOS over TCP/IP name tables; WINIPCFG existed on Windows 9x (GUI), not on NT-class systems; PING tests reachability but does not show local configuration. Step-by-Step Solution: State requirement: view local IP configuration parameters.Map to tool: IPCONFIG or IPCONFIG /ALL provides exactly that.Eliminate tools meant for connections, NetBIOS, GUI-only on 9x, or reachability tests.Select IPCONFIG. Verification / Alternative check: Windows documentation and help text (ipconfig /?) confirm this usage. Modern equivalents persist across Windows versions, making IPCONFIG the canonical choice. Why Other Options Are Wrong: NBTSTAT: NetBIOS name tables, not IP config. NETSTAT: sockets and routes, not assigned addresses. WINIPCFG: Windows 9x GUI utility, not NT. PING: reachability test, not configuration display. Common Pitfalls: Confusing netstat -r (route table) with IP address assignment; expecting ping to reveal local addresses; using winipcfg on NT where it is unavailable. Final Answer: IPCONFIG.

Question 5

On X.25 public data networks, which device enables asynchronous character-mode terminals to access the packet network by assembling and disassembling packets on their behalf?

Accepted Answer

Introduction / Context: X.25 was designed for packet-switched public data networks, but many end users connected using asynchronous character-mode terminals. These devices could not speak packet protocols directly, so an intermediary was needed to buffer characters, handle line editing, and translate between character streams and packet flows. This question asks you to name that intermediary device. Given Data / Assumptions: Terminals are asynchronous (start-stop), not synchronous packet devices. Network is X.25, using virtual circuits and packet layer procedures. A device must translate between terminal I/O and X.25 PLP traffic. Concept / Approach: The Packet Assembler/Disassembler (PAD) accepts characters from an asynchronous terminal, assembles them into X.25 packets with appropriate control and addressing, and sends them into the network. In the reverse direction, it disassembles received packets back into characters for the terminal. PAD behavior was standardized (e.g., X.3 for parameters, X.28/X.29 for access procedures) to provide consistent features across providers. Step-by-Step Solution: Identify mismatch: async terminals vs. packet network.Recall standardized solution: PAD translates characters ↔ packets.Map standards: X.3/X.28/X.29 define PAD parameters and exchanges.Select “Packet assembler/disassembler (PAD).” Verification / Alternative check: Historical network service manuals list PAD nodes as access points for dial-up terminals, showing configuration of PAD parameters such as local echo, editing, idle timers, and packetization thresholds. Why Other Options Are Wrong: Repeater: regenerates signals; no protocol translation. Bridges: Layer-2 devices; do not convert async characters to X.25 packets. Gateway: generic term; not the specific standardized device for X.25 terminal access. None of the above: incorrect because PAD is correct. Common Pitfalls: Confusing PADs with modems; assuming “gateway” is specific enough—PAD is the precise, standards-based term in X.25 contexts. Final Answer: Packet assembler/disassembler (PAD).

Question 6

Which of the following are examples of bounded (guided) transmission media used to carry signals along a defined physical path?

Accepted Answer

Introduction / Context: Physical communication media are broadly categorized as bounded (guided) or unbounded (unguided). Bounded media confine electromagnetic energy to a physical path, while unbounded media radiate through free space. Recognizing common examples of guided media is fundamental for selecting cabling and planning link budgets. This question asks you to identify which listed items qualify as bounded media. Given Data / Assumptions: We consider typical guided media used in networking and microwave links. Bounded media should constrain propagation within a physical structure. Each option is evaluated for whether it guides energy along a defined path. Concept / Approach: Coaxial cable guides signals between an inner conductor and shield with controlled impedance. Waveguides (rectangular or circular) confine microwave energy within conducting walls, supporting discrete propagation modes across set frequency bands. Fiber-optic cable guides light through total internal reflection in a glass core surrounded by cladding. All three are classic examples of bounded media. Therefore, the correct choice is “All of the above.” Step-by-Step Solution: Assess coax: metal conductors and dielectric guide RF—bounded.Assess waveguide: hollow conductor confines fields—bounded.Assess fiber: glass core/cladding guides light—bounded.Conclude that all listed items are bounded media. Verification / Alternative check: Standards and textbooks group twisted pair, coaxial cable, optical fiber, and waveguides under guided media, in contrast to radio, microwave, and infrared free-space links as unguided media. Why Other Options Are Wrong: Each single item alone is a subset; the comprehensive correct answer is all listed items. None of the above is incorrect because all listed examples are guided media. Common Pitfalls: Misclassifying waveguides as “antennas” rather than as guided structures; forgetting that fiber is also bounded even though it uses light instead of electrical currents. Final Answer: All of the above.

Question 7

In IEEE 802 LAN standards, the Data Link layer is split into two sublayers for clarity of responsibilities. Which names correctly identify the upper sublayer and the lower sublayer, respectively?

Accepted Answer

Introduction / Context: Local Area Network (LAN) standards from IEEE project 802 refine the classic OSI Data Link layer by splitting it into two logical parts. This split helps vendors and engineers cleanly separate concerns: one sublayer focuses on addressing and media access to the physical medium, while the other offers a uniform service interface and control to higher layers regardless of the underlying media details. Given Data / Assumptions: The question refers to IEEE 802 LAN architecture. We must name the upper and lower Data Link sublayers in their correct order. Common LANs (Ethernet, Wi-Fi, Token Ring historically) follow this structure. Concept / Approach: IEEE 802 defines the Logical Link Control (LLC) as the upper sublayer and the Media Access Control (MAC) as the lower sublayer. The LLC sublayer provides a consistent interface (service access points, flow/error control primitives) to the Network layer. The MAC sublayer implements addressing (e.g., 48-bit MAC addresses) and media access rules (CSMA/CD, CSMA/CA, token passing, etc.). Step-by-Step Solution: Identify the role of the upper sublayer: uniform services to Layer 3 → LLC.Identify the role of the lower sublayer: frame formatting, media access, addressing → MAC.Map to options in correct order: upper = LLC, lower = MAC. Verification / Alternative check: Ethernet frames include a MAC header/footer handled by MAC; LLC (historically IEEE 802.2) sits above and can multiplex protocols such as IP and IPX via Service Access Point (SAP) values, though modern Ethernet commonly uses EtherType directly (bypassing classic LLC for many protocols). The architectural split, however, remains core to IEEE 802 documentation and pedagogy. Why Other Options Are Wrong: HDLC/PDU or PDU/HDLC: HDLC is a distinct bit-oriented protocol, and PDU is a generic term for protocol data unit, not a sublayer. MAC, LLC: Reversed order; MAC is lower, LLC is upper. None of the above: Incorrect because LLC (upper) and MAC (lower) is the standard answer. Common Pitfalls: Confusing OSI Data Link framing with IEEE’s sublayer split; remember that “LLC on top, MAC below” is the canonical mapping used in 802 LANs. Final Answer: LLC, MAC

Question 8

In radio-spectrum terminology for communications engineering, which named frequency band is widely used for television broadcasting and many low-power microwave applications?

Accepted Answer

Introduction / Context: The radio spectrum is divided into standardized bands with typical applications assigned to each. Understanding which band supports broadcast television and many short-range microwave links is essential in networking, wireless design, and regulatory planning (e.g., antenna selection, link budgets, and interference analysis). Given Data / Assumptions: We seek the named frequency range that fits television transmission and low-power microwave uses. Band names follow ITU/IEEE conventions. Options list canonical numeric ranges in MHz. Concept / Approach: Ultra High Frequency (UHF) spans 300 MHz to 3000 MHz (0.3–3 GHz). Broadcast TV allocations occupy portions of UHF (and historically parts of VHF). Many short-range microwave, cordless, and ISM applications (e.g., 433 MHz, 868/915 MHz, 2.4 GHz) are also in UHF. Super High Frequency (3–30 GHz) covers higher-frequency microwave and satellite bands, but the question emphasises TV and low-power microwave, which commonly reside in UHF. Step-by-Step Solution: Match “TV broadcasting + low-power microwave” to band usage patterns.Recall UHF numeric limits: 300–3000 MHz.Select the option that states this range explicitly. Verification / Alternative check: Digital terrestrial TV (DTT) channels operate widely in UHF. Wi-Fi at 2.4 GHz, Bluetooth, and many ISM devices also sit within the UHF boundary (upper end), illustrating the band’s relevance to “low-power microwave-like” consumer applications. Why Other Options Are Wrong: Very Low Frequency and Medium Frequency are far too low; they are used for long-wave, AM broadcast, maritime, and navigation services. Super High Frequency begins at 3 GHz; many TV allocations and low-power consumer radios fall below this threshold. None of the above: Incorrect because UHF is the well-known answer. Common Pitfalls: Confusing the terms “microwave” broadly (often >1 GHz) with the specific named bands; although some microwave definitions overlap with UHF, TV and numerous low-power devices live squarely in UHF. Final Answer: Ultra High Frequency: 300 MHz to 3000 MHz

Question 9

In classical TCP/IP networks, which protocol does a diskless client use to discover its Internet Protocol (IP) address from a local server when it only knows its hardware (MAC) address?

Accepted Answer

Introduction / Context: Before DHCP became ubiquitous, early workstations often booted over the network without any preconfigured IP address. They needed a protocol that could map a known MAC address to an appropriate IP address, enabling the boot process to continue and higher-layer configurations to load. Given Data / Assumptions: The client has only its link-layer identity (MAC address). Objective: obtain an IP address from a server on the same LAN. Context: legacy TCP/IP (RARP/BOOTP era) rather than modern DHCP-only environments. Concept / Approach: Reverse Address Resolution Protocol (RARP) performs the inverse of ARP: it queries a RARP server with a MAC address and receives the corresponding IP address. BOOTP and DHCP later generalized and extended this function, but the direct historical answer to “MAC → IP” is RARP. Step-by-Step Solution: Identify the mapping direction required: MAC → IP.Match to protocol designed for this purpose: RARP.Exclude routing (RIP), remote desktop (RDP), and packet-switched link standards (X.25) as unrelated. Verification / Alternative check: In many textbooks, the boot sequence for diskless clients begins with a RARP request, followed by TFTP image retrieval; modern stacks replace RARP with DHCP/BOOTP but the principle remains similar. Why Other Options Are Wrong: RDP: Remote Desktop Protocol; unrelated to address discovery. RIP: Routing Information Protocol; distributes routes, not host addresses. X.25: Packet-switched network suite; not an IP address assignment mechanism. None of the above: Incorrect because RARP is correct. Common Pitfalls: Confusing ARP (IP → MAC) with RARP (MAC → IP). The word “Reverse” is the key memory cue. Final Answer: RARP

Question 10

On a DHCP-configured Windows client, what single piece of status information is explicitly indicated in the Network Properties dialog when the system is obtaining its address dynamically?

Accepted Answer

Introduction / Context: Windows clients can acquire IP configuration either statically or dynamically. The Network Properties dialog (adapter settings) distinguishes between manual configuration and automatic configuration through Dynamic Host Configuration Protocol (DHCP). Recognizing this status is useful when troubleshooting address assignment issues. Given Data / Assumptions: The client receives its IP configuration from a DHCP server. We are focusing on what the Network Properties dialog explicitly conveys as a single, generic status item. Not all specific values (IP, gateway) are necessarily shown in that brief properties pane without drilling deeper (e.g., via ipconfig/details or the Status → Details view). Concept / Approach: At a high level, the properties UI indicates that the interface is set to “Obtain an IP address automatically,” which semantically means the client is using DHCP. While the actual numeric IP, subnet mask, and default gateway can be viewed in detailed status dialogs, the primary properties view highlights the DHCP-based configuration method rather than enumerating all parameters. Step-by-Step Solution: Open adapter properties and observe addressing method.Identify “Obtain an IP address automatically” / “DHCP enabled.”Conclude that the clear information conveyed is that the client is receiving its address from DHCP. Verification / Alternative check: Running “ipconfig /all” shows “DHCP Enabled: Yes” and additional details (lease obtained/expires, DHCP server). The brief properties view is consistent with this dynamic status without always displaying all specific numbers in one place. Why Other Options Are Wrong: The IP address, subnet, and default gateway values may not be directly summarized in the basic properties selection; those are detailed values, not the singular status message about sourcing from DHCP. None of the above: Incorrect since the dialog clearly indicates a DHCP-based configuration. Common Pitfalls: Assuming the basic properties window must display all numeric parameters; that requires viewing the connection status details or command-line output. Final Answer: That the client is receiving its address from DHCP

Question 11

Identify the network model in which end-user workstations connect to Local Area Network (LAN) servers to share resources and offload application processing to server components.

Accepted Answer

Introduction / Context: Networked applications commonly follow the client/server paradigm: desktop or mobile clients consume services exposed by server processes over a LAN or WAN. This architecture centralizes data, security, and compute-intensive tasks while providing users with responsive interfaces and shared resources such as files, printers, databases, and web services. Given Data / Assumptions: End-user workstations are connected to LAN servers. Goals include resource sharing and application processing split between client and server. We are naming the architectural model. Concept / Approach: Client/Server networks define a clear separation of roles: clients present the UI and make requests; servers handle centralized services (authentication, storage, application logic). This improves manageability, scalability, and security compared to purely peer-to-peer arrangements. The term “internetworked enterprise” is broader and does not uniquely describe this split; “information superhighway” is a historic media metaphor, not an architecture. Step-by-Step Solution: Map the described resource sharing and processing split to the client/server pattern.Confirm that LAN servers provide services (e.g., file, print, directory, database, web).Select “Client/Server networks.” Verification / Alternative check: Examples include web applications (browser clients to web/app servers), SMB/NFS file services, and database clients connecting to RDBMS servers. Windows domains and Linux directory services (e.g., Active Directory, LDAP) are emblematic of client/server setups. Why Other Options Are Wrong: Internetworked enterprise: Describes organizational scope, not this specific architecture. Information superhighway: A colloquial phrase for the Internet, not a network model. Business applications of telecommunications: A broad category, not the targeted architecture term. None of the above: Incorrect because client/server is precisely what is described. Common Pitfalls: Confusing client/server with peer-to-peer; in client/server, servers are authoritative sources of services and data. Final Answer: Client/Server networks

Question 12

Two computers exchange ASCII messages using a simple parity check (single parity bit per block). Which error pattern will always remain undetected by this parity method?

Accepted Answer

Introduction / Context: A simple parity check appends one parity bit so that the total number of 1s in a protected block is always even (even parity) or always odd (odd parity). The receiver recomputes the parity and flags an error if the parity does not match. While parity is inexpensive, it cannot detect all error patterns. Given Data / Assumptions: ASCII transmission with a single parity bit per protected block (byte or larger block as defined). Parity decision rule: detect a mismatch in overall parity. We consider arbitrary bit inversions during transmission. Concept / Approach: Parity detects any error pattern that flips an odd number of bits, because an odd-bit flip toggles overall parity. Conversely, flipping an even number of bits leaves the parity unchanged, so the receiver sees a “valid” parity and accepts a corrupted block—an undetected error. This limitation motivates stronger error-detection codes such as checksums and CRCs. Step-by-Step Solution: Assume even parity for concreteness; the argument is symmetrical for odd parity.If 1, 3, 5, ... bits flip → total count of 1s changes by an odd number → parity toggles → error detected.If 2, 4, 6, ... bits flip → total count changes by an even number → parity unchanged → error undetected. Verification / Alternative check: Consider a simple 7-bit ASCII character plus parity. Flipping any two bits within the protected unit results in the same overall parity state. Generalizing to a whole block protected by one parity bit yields the same conclusion. Why Other Options Are Wrong: Odd-bit inversions (options a and c) are always detected because parity flips. Even-bit inversions limited to a single byte (option d) are a subset of the more general undetectable pattern across the block; the question asks for what “will always” be undetected, and the correct, general statement is the even-bit case across the protected block. None of the above: Incorrect because even-bit errors are the known blind spot. Common Pitfalls: Thinking parity can locate the bit in error—it cannot; it only signals presence/absence of an error and completely misses even-bit flips. Final Answer: Two bits or any even number of bits inverted in a block

Question 13

In data communications, a circuit that permits data transmission in both directions but not simultaneously is operating in which mode?

Accepted Answer

Introduction / Context: Duplexing determines whether communication endpoints can send and receive at the same time. Selecting the right duplex mode matters for throughput, latency, and protocol design. Many legacy and wireless systems rely on half-duplex operation to share a medium efficiently. Given Data / Assumptions: The link supports bidirectional transmission. Simultaneous two-way transmission is not allowed. We need the standard term that describes this constraint. Concept / Approach: Simplex allows transmission in only one direction. Half-duplex allows both directions but requires taking turns (time-sharing the medium). Full-duplex allows simultaneous transmission and reception, typically over separate channels or using echo cancellation. Therefore, “both directions but not at the same time” precisely defines half-duplex. Step-by-Step Solution: Interpret the phrase “both directions but not simultaneously.”Map to “half-duplex” by definition.Exclude simplex (one-way only) and full-duplex (simultaneous two-way). Verification / Alternative check: Analogy: A walkie-talkie Push-to-Talk system is half-duplex—users alternate speaking. A telephone call is full-duplex—both parties can talk and hear concurrently. Why Other Options Are Wrong: Simplex: Unidirectional only, not bidirectional. Full-duplex: Allows simultaneous two-way, contradicting the question. Asynchronous: Refers to timing without a shared clock, not duplex capability. None of the above: Incorrect because half-duplex fits exactly. Common Pitfalls: Confusing duplex mode with synchronous/asynchronous timing; they are orthogonal properties of a link. Final Answer: a half-duplex mode

Question 14

You are assigned an address block beginning with a Class C range (first octet 200.x.x.x) and currently require at least 10 subnets. To maximize the number of usable hosts per subnet while meeting this requirement, which subnet mask (last-octet value…

Accepted Answer

Introduction / Context: Subnet design for a Class C-sized block (default /24) trades the number of subnets against hosts per subnet. Borrowing more bits increases the number of subnets but decreases hosts per subnet. The goal is to satisfy a required minimum number of subnets (here, 10) while leaving the host count as large as possible. Given Data / Assumptions: Base network resembles a /24 (first octet in the 200 range). At least 10 subnets are required now. We want to maximize usable hosts per subnet subject to that constraint. All-zeros and all-ones subnets are usable (modern practice). Concept / Approach: For a /24, the host portion is 8 bits. Borrow s bits to form subnets: number_of_subnets = 2^s. We need 2^s ≥ 10 → s = 4 (since 2^3 = 8 is insufficient; 2^4 = 16 meets the need). The new prefix is /28 (24 + 4). In dotted-decimal, /28 corresponds to 255.255.255.240, so the last-octet mask value is 240. Usable hosts per /28 subnet are 2^(8 − 4) − 2 = 14, which is larger than for /29 (6) or /30 (2). Step-by-Step Solution: Find s such that 2^s ≥ 10 → s = 4.Compute prefix: 24 + 4 = /28.Map /28 to last-octet mask value: 240.Confirm hosts per subnet: 14 usable, maximized among qualifying masks. Verification / Alternative check: Lesser masks: 224 (/27) → 8 subnets (not enough). Heavier masks: 248 (/29) or 252 (/30) meet subnets but reduce hosts to 6 or 2, violating the “maximize hosts” objective. Why Other Options Are Wrong: 192 (/26) and 224 (/27): Provide 4 or 8 subnets—insufficient. 248 (/29) and 252 (/30): Provide 32 or 64 subnets but at the cost of too few hosts per subnet. Common Pitfalls: Forgetting that the minimum s must satisfy the current requirement; borrowing more bits than necessary needlessly shrinks subnets. Final Answer: 240

Question 15

Within the TCP/IP suite, which protocol is specifically designed for transferring files reliably between networked hosts using a client–server model?

Accepted Answer

Introduction / Context: File transfer is a fundamental network service. The classic Internet protocol that provides interactive directory listing, file upload/download, and control commands across hosts is the File Transfer Protocol (FTP). It sits above TCP to ensure reliable delivery of control and data streams. Given Data / Assumptions: We need the protocol name, not merely the transport it uses. Focus is on standardized client–server file transfer features. Other listed protocols serve different purposes in the TCP/IP stack. Concept / Approach: FTP uses two TCP connections (control and data) to exchange commands and files. It supports authentication, ASCII/binary modes, and active/passive data channel setup. While HTTP, SFTP, and SCP are modern alternatives, FTP is the canonical protocol explicitly named for file transfer in the TCP/IP suite. Step-by-Step Solution: Identify the need: transfer files between hosts.Select the application-layer protocol: FTP.Differentiate from ARP/RARP (address resolution) and TCP (transport only). Verification / Alternative check: FTP clients (e.g., command-line ftp) and servers (vsftpd, IIS FTP) exemplify this model. Reliability stems from TCP; the protocol adds the semantics for file operations. Why Other Options Are Wrong: RARP/ARP: Map addresses between layers; they do not transfer files. TCP: Transport protocol; not itself a file transfer application protocol. None of the above: Incorrect because FTP is precisely designed for this purpose. Common Pitfalls: Equating “uses TCP” with being a file-transfer protocol; many applications use TCP, but only FTP provides the file command set. Final Answer: FTP

Question 16

In the OSI network architecture, which layer is responsible for dialogue control between applications (e.g., establishing who speaks when) and token management for orderly communication?

Accepted Answer

Introduction / Context: The OSI model separates communication functions across seven layers. Above reliable data delivery, applications still need coordination: determining turn-taking, resynchronization after interruptions, and orderly exchange of data units during complex interactions. These coordination tasks are grouped in a specific OSI layer. Given Data / Assumptions: “Dialogue control” means managing who transmits at a given time in a session. “Token management” refers to granting and passing permission to speak in a structured interaction. We are mapping these responsibilities to a single OSI layer. Concept / Approach: The Session layer (Layer 5) establishes, manages, and terminates sessions between applications. It provides dialog control (half-duplex/full-duplex conventions at the application dialog level), token management to avoid conflicts in conversational exchanges, and synchronization via checkpoints. Transport (Layer 4) ensures reliable end-to-end data delivery; Network (Layer 3) routes packets; Data Link (Layer 2) frames and controls access to the physical medium. Step-by-Step Solution: Identify that the problem is coordination of application-level conversation, not packet delivery.Recall that OSI Layer 5 (Session) handles dialog and tokens.Exclude Layers 2–4 as they serve lower-level delivery and framing functions. Verification / Alternative check: Session services include full/half-duplex dialog conventions, activity management, and synchronization points that allow resuming after transient failures—functions distinct from transport reliability or network routing. Why Other Options Are Wrong: Network: Concerned with logical addressing and routing, not application dialog. Transport: Provides segmentation, flow control, and error recovery, not tokenized dialog control. Data Link: Manages frames on a local link, not inter-application sessions. None of the above: Incorrect because “session layer” is the standard answer. Common Pitfalls: Attributing dialog control to Transport; while Transport ensures delivery, it does not orchestrate “who speaks when” at the application level. Final Answer: session layer

Question 17

In computer networking, what was the main reason for creating the OSI (Open Systems Interconnection) reference model?

Accepted Answer

Introduction / Context: The OSI reference model is a conceptual framework that divides networking functions into seven layers, from physical transmission up to application services. It was developed by the International Organization for Standardization to guide the design of networking protocols and equipment. This question asks why the OSI model was introduced in the first place. Given Data / Assumptions: Different vendors were creating proprietary networking solutions that did not always work together. There was a need for a common language to describe networking functions. Standardization helps achieve interoperability between systems. Concept / Approach: The OSI model does not specify a single protocol. Instead, it describes layers and the functions that should be performed at each layer. Vendors and standards bodies can then design specific protocols that fit into these layers. By following the OSI layered approach, hardware and software from different manufacturers can interoperate more easily, provided they implement compatible protocols at the corresponding layers. This layered view also makes it easier to understand, design, and troubleshoot complex networks. Step-by-Step Solution: Step 1: Recognize that the primary goal of OSI was to promote openness and interoperability between different systems and vendors.Step 2: Understand that the model defines a common structure with seven layers, each with its own responsibilities.Step 3: Note that the OSI model did not instantly replace all existing protocols but provided a guide for future protocol development.Step 4: Choose the option that clearly states that OSI provides a standard layered framework for interoperable design. Verification / Alternative check: Consider how networking is taught and documented today. Engineers refer to terms like layer two switches, layer three routers, and layer seven firewalls, which come directly from OSI concepts. Although modern internet protocols more closely follow the TCP or IP model, the OSI layers are still used as a reference. This continued use as a standard framework confirms that providing a common model was the OSI model's main purpose. Why Other Options Are Wrong: Option B: Suggests that OSI was meant to instantly replace all protocols with one universal protocol, which was never realistic or intended.Option C: Limits OSI to physical cabling, ignoring the higher layers, which contradicts the seven layer structure.Option D: Claims that OSI was made to restrict networking to a single vendor, which goes against the idea of open systems and interoperability. Common Pitfalls: Students sometimes think that OSI is itself a protocol stack that all networks must implement. In reality, it is a reference model. Actual protocol suites, such as TCP or IP, can be mapped to the OSI layers conceptually but do not match it exactly. Keeping this distinction in mind helps avoid confusion when reading exam questions and technical documentation. Final Answer: The correct answer is To provide a standard layered framework that helps different vendors design interoperable network hardware and software.

Question 18

In computer networking, the physical or logical arrangement of devices and communication links in a network is called its what?

Accepted Answer

Introduction / Context: When describing networks, it is important to distinguish between how devices are arranged and how data is actually forwarded. The term topology refers to the arrangement of nodes and links, either as they are physically connected or as they appear logically to higher layers. This question checks whether you know the correct term for that arrangement. Given Data / Assumptions: We are dealing with basic networking terminology. Networks can be arranged in star, bus, ring, mesh, and other patterns. Routing is a separate process that decides the paths that packets take through the network. Concept / Approach: Network topology is the term used for describing the pattern of connections between devices. Physical topology focuses on actual cable and hardware connections, while logical topology describes how data flows, which may differ from the physical layout. Examples include star topology where all devices connect to a central switch, and bus topology where all devices share a common backbone. Routing deals with selecting specific paths for data packets, often using tables and algorithms, but does not define the overall arrangement itself. Step-by-Step Solution: Step 1: Identify that the question is asking about arrangement, which is related to the structure or pattern of the network.Step 2: Recall that the term network topology is widely used for physical and logical layouts.Step 3: Understand that routing is the process of choosing paths, not defining the layout itself.Step 4: Recognize that networking is a broad term and not specific enough for this definition.Step 5: Choose topology as the correct term for the arrangement of devices and links. Verification / Alternative check: Textbooks and exam syllabi list common topologies such as star, bus, ring, mesh, and tree. Each of these describes how nodes are interconnected. In contrast, routing protocols such as RIP, OSPF, or BGP decide how to forward packets through this structure. This clear division confirms that topology is the correct answer for the layout concept. Why Other Options Are Wrong: Option B: Routing is about path selection and packet forwarding, not about the overall arrangement.Option C: Saying both topology and routing blurs the distinction; only topology matches the question's definition.Option D: Networking is a general term for the field and does not specifically describe the arrangement of nodes. Common Pitfalls: Some learners use topology and routing loosely, but in exam settings you must use precise terms. Another pitfall is to think that topology only refers to physical cabling. Logical topology is equally important, especially in switched and wireless networks where the physical layout may not reflect the logical connections used for data flow. Final Answer: The correct answer is Topology.

Question 19

In fiber optic communication, what is cladding and why is it used around the fiber core?

Accepted Answer

Introduction / Context: Fiber optic cables transmit data as pulses of light through very thin glass or plastic fibers. The internal structure of a fiber includes a central core and a surrounding cladding. Both parts play important roles in guiding light and maintaining signal quality. This question asks you to explain what cladding is and why it is necessary. Given Data / Assumptions: A fiber optic strand has a central core through which light travels. The core is surrounded by cladding made of a different optical material. The refractive index of the cladding is slightly lower than that of the core. Concept / Approach: In fiber optics, light is guided along the core using the principle of total internal reflection. For this to happen, the core must have a higher refractive index than the surrounding material. The cladding is designed with a slightly lower refractive index so that light striking the core boundary at shallow angles is reflected back into the core instead of escaping. This guidance mechanism allows light pulses to travel long distances with low loss and reduced interference between adjacent fibers. The cladding also provides mechanical protection and helps maintain the correct numerical aperture of the fiber. Step-by-Step Solution: Step 1: Recognize that cladding is an integral optical layer, not just an external plastic jacket.Step 2: Recall that the refractive index of the cladding is intentionally made lower than that of the core.Step 3: Understand that this refractive index difference causes total internal reflection at the core cladding boundary.Step 4: Note that total internal reflection keeps light confined within the core, allowing efficient signal transmission.Step 5: Choose the option that correctly describes the cladding as a surrounding layer that helps guide light by total internal reflection. Verification / Alternative check: Fiber specifications often list core diameter, cladding diameter, and numerical aperture. For example, a common multimode fiber might be labeled 62.5 or 125, indicating a core of 62.5 micrometers surrounded by cladding of 125 micrometers. The difference in refractive indices is carefully controlled during manufacturing. Optical diagrams in textbooks show rays bouncing within the core because the cladding keeps them confined. These details confirm the role of cladding as described in the correct option. Why Other Options Are Wrong: Option B: Describes shielding in copper cables, not the optical cladding in fiber.Option C: Refers to an outer plastic jacket, which protects the cable mechanically but is not called cladding in optical terms.Option D: Talks about adhesive used during splicing, which is not the same as the structural cladding layer. Common Pitfalls: Students sometimes think of cladding as just mechanical protection. While it does contribute to strength, its primary role is optical, ensuring correct light guidance. Another pitfall is forgetting that the core and cladding must have specific refractive index values. If the indices are not properly chosen, the fiber will not guide light efficiently and losses will increase. Final Answer: The correct answer is An outer layer of glass or plastic surrounding the fiber core with a lower refractive index that keeps light signals confined within the core by total internal reflection.

Question 20

In the TCP or IP protocol suite, what are the typical names of the data units used at different layers (application, transport, internet, and network access)?

Accepted Answer

Introduction / Context: In layered network models, each layer has its own terminology for the unit of data that it processes. Understanding these terms helps you read protocol descriptions and troubleshoot communication problems. The TCP or IP protocol suite uses a four or five layer view, which can be mapped to the OSI model. This question checks whether you know the standard names for data units at major layers. Given Data / Assumptions: We are considering the TCP or IP suite with application, transport, internet, and network access layers. The physical layer deals with raw bits on the medium. Different layers may add or remove headers and trailers to form their respective data units. Concept / Approach: At the application layer, the protocol deals with data or messages as supplied by the application. When this data is passed down to the transport layer, it is encapsulated into segments (for TCP) or datagrams (for UDP). The internet layer treats these as packets, adding IP headers that include source and destination IP addresses. At the network access or data link layer, packets are carried inside frames that include hardware addressing and error detection fields. Finally, at the physical layer, frames are converted into a stream of bits and transmitted as electrical, optical, or radio signals. Step-by-Step Solution: Step 1: Start at the top. Application layer deals with data or messages, not low level units.Step 2: At the transport layer, recall that TCP uses the term segment, while UDP uses the term datagram.Step 3: At the internet layer, which uses IP, the data unit is commonly called an IP packet.Step 4: At the network access or data link layer, the data unit is a frame, which includes MAC addresses and error checking.Step 5: At the physical layer, all of this information is converted into raw bits on the medium.Step 6: Choose the option that lists data or message, segment or datagram, packet, frame, and bits in this order. Verification / Alternative check: Networking textbooks and certification materials often use the phrase data, segment, packet, frame, bits as a mnemonic for moving down the stack. Diagrams show encapsulation where each layer adds its own header to the unit it receives from the layer above. For example, the transport layer adds a TCP header to application data to form a segment, and the IP layer adds an IP header to form a packet. This consistent naming scheme matches the description in the correct option. Why Other Options Are Wrong: Option B: Assigns bits to the application layer and frames to the transport layer, which reverses the correct order and does not match standard terminology.Option C: Uses the wrong terms at each layer and confuses segments, packets, and frames.Option D: Suggests that all layers use the term file, which is not accurate; files are operating system level objects, not protocol data units. Common Pitfalls: A common mistake is mixing up segments and packets or frames, especially when moving between OSI and TCP or IP terminology. Another pitfall is forgetting that the physical layer deals with bits, not with packets or frames. Remembering the sequence data, segment, packet, frame, bits is a helpful way to keep everything in order. Final Answer: The correct answer is Application layer: data or message, Transport layer: segment or datagram, Internet layer: packet, Network access layer: frame, Physical layer: bits.

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