Q: Your company operates two separate LANs (downtown office and a suburban plant). To share data and resources between these LANs over an internetwork, which device is most appropriate?

Introduction / Context: Interconnecting distinct LANs across sites requires a device that forwards traffic at the network layer and can select paths between different IP subnets. This is a classic use case for routing rather than simple Layer-2 extension. Given Data / Assumptions: Two geographically separated LANs exist (downtown and suburban plant). Goal is to exchange IP traffic between different subnets. Connectivity likely traverses a WAN link or VPN. Concept / Approach: Routers operate at OSI Layer 3, maintain routes, and forward packets between networks with different subnets. They can establish site-to-site VPNs or use dedicated WAN links. Hubs and simple cables do not provide Layer-3 forwarding. Bridges connect Layer-2 segments within the same broadcast domain and are not ideal for routed, multi-site internetworking. Step-by-Step Solution: Step 1: Identify that traffic must cross IP subnet boundaries between sites.Step 2: Select a Layer-3 device capable of path selection and inter-subnet forwarding.Step 3: Choose router as the appropriate device.Step 4: Note that modern implementations may use firewalls or SD-WAN appliances that include routing functions. Verification / Alternative check: Enterprise networks universally route between sites using routers or routing-capable security appliances. This validates the choice. Why Other Options Are Wrong: Modem: Provides line signaling for WAN access but not full inter-LAN routing by itself. Cable: A medium, not a routing device. Hub: Layer-1 repeater; no IP forwarding. Bridge: Layer-2 only; unsuitable for scalable multi-site interconnection. Common Pitfalls: Assuming any interconnect device suffices. Multi-site communication requires Layer-3 routing and often security policies, which routers provide. Final Answer: Router

Q: Telecommunication networks that connect an organization with its external customers and suppliers are best described as which of the following?

Introduction / Context: Organizations increasingly integrate information systems with external stakeholders. The term for a private, controlled network that extends a company’s internal services to partners, suppliers, and customers is a foundational concept in enterprise networking strategy. Given Data / Assumptions: Focus is on connections that cross organizational boundaries. Security, access control, and selective sharing are important. The solution complements, not replaces, the internal intranet. Concept / Approach: An extranet is an extension of an intranet that provides authorized external entities with secure access to selected internal resources. This is commonly implemented with VPNs, identity federation, and web portals, enabling collaboration such as order tracking, inventory visibility, and joint project work. Step-by-Step Solution: Step 1: Recognize the scope: connection with customers and suppliers, not only internal users.Step 2: Map to established terminology: the standard term is 'extranet.'Step 3: Validate that extranets provide selective, authenticated access beyond the company firewall.Step 4: Conclude that 'Extranets' is the best fit among the options. Verification / Alternative check: Industry practice shows business-to-business portals branded as partner extranets, confirming the terminology. Why Other Options Are Wrong: Bandwidth alternatives: Refers to capacity choices, not inter-organizational connectivity. Switching alternating: Not a standard term. Inter organizational networks: Generic phrase, but the precise, widely used term is 'extranet.' None of the above: Incorrect because 'Extranets' is correct. Common Pitfalls: Confusing extranets with the public Internet (open access) or with intranets (internal only). Extranets are private, controlled extensions to specific outside entities. Final Answer: Extranets

Q: In TCP/IP networking (IPv4), how many bits are assigned to the Internet address of a host, which is used in all communications with that host?

Introduction / Context: IPv4 addressing is the classic scheme for identifying hosts and interfaces on TCP/IP networks. Each IPv4 address uniquely identifies a destination for packets across routed networks. Knowing the bit-length of this address is a foundational networking fact tested in many exams and interviews. Given Data / Assumptions: The question specifically concerns the IPv4 Internet (not IPv6). The address is the one used in all communications with the host. We assume standard dotted-decimal notation corresponds to a fixed-length binary address. Concept / Approach: IPv4 uses a fixed 32-bit address. In dotted-decimal form, this is written as four octets (for example, 192.168.1.10). The 32-bit space provides approximately 4.29 billion unique combinations (subject to reservation and subnetting). IPv6, by contrast, uses 128 bits, but it is not the subject of this question. Step-by-Step Solution: Recall definition: IPv4 address length = 32 bits.Map to human-readable form: 4 octets * 8 bits per octet = 32 bits.Confirm usage: This address is carried in the IP header for routing decisions.Select the option stating 32 - bits. Verification / Alternative check: Inspect any IPv4 packet capture: fields 'Source Address' and 'Destination Address' are 32 bits each. Networking APIs (for example, sockaddr_in) also model IPv4 addresses as 32-bit values. Why Other Options Are Wrong: 16 - bits / 48 - bits / 64 - bits: These sizes correspond to other identifiers (for example, port numbers are 16-bit; MAC addresses are 48-bit; IPv6 is 128-bit, not 64-bit). None of the above: Incorrect because 32 - bits is correct for IPv4. Common Pitfalls: Mixing up MAC address length (48 bits) with IP address length (32 bits) or confusing IPv4 with IPv6. Final Answer: 32 - bits

Q: For a noiseless channel of bandwidth 3 kHz transmitting binary level signals, what is the maximum theoretical data rate according to the Nyquist criterion?

Introduction / Context: The Nyquist criterion provides an upper bound on the data rate for a noiseless channel given a limited bandwidth and a specified number of discrete signaling levels. This question asks you to apply the Nyquist formula to a 3 kHz channel using binary signaling (two levels) to find the maximum bit rate in bits per second (bps). Given Data / Assumptions: Channel bandwidth B = 3 kHz (that is, 3000 Hz). Number of signal levels M = 2 (binary). The channel is idealized as noiseless; intersymbol interference is neglected under Nyquist sampling. Concept / Approach: Nyquist maximum data rate for a noiseless channel is given by: R_max = 2 * B * log2(M) For binary signaling (M = 2), log2(2) = 1, so the formula simplifies to: R_max = 2 * B Substituting B = 3000 Hz yields 6000 bps, which is 6 Kbps. Step-by-Step Solution: Write the formula: R_max = 2 * B * log2(M)Insert values: R_max = 2 * 3000 * log2(2)Compute log2(2) = 1 → R_max = 2 * 3000 * 1Compute numeric result: R_max = 6000 bps = 6 Kbps Verification / Alternative check: Compare with higher-level modulation: if M = 4 (quaternary), R_max would double to 12 Kbps for the same bandwidth, confirming that binary (M = 2) gives 6 Kbps at 3 kHz. Why Other Options Are Wrong: 3 Kbps: Misses the factor of 2 in the Nyquist formula for baseband signaling. 12 Kbps / 24 Kbps: These would require higher M (more levels) or additional assumptions; they exceed the binary case. None of the above: Incorrect because 6 Kbps is exactly the Nyquist limit here. Common Pitfalls: Confusing Nyquist's noiseless limit with Shannon's noisy-channel capacity, or forgetting that binary signaling (M = 2) makes log2(M) equal to 1. Final Answer: 6 Kbps

Q: Which networking device is used to connect two systems when the systems may use different protocols, performing necessary translation at higher layers?

Introduction / Context: Interconnecting heterogeneous networks often requires more than simple electrical or frame-level forwarding. When two systems speak different protocols, a device that operates at higher layers must translate or mediate between them so applications can communicate transparently. Given Data / Assumptions: Two systems or networks may use different upper-layer protocols. The goal is to enable communication despite these differences. We compare common devices: repeater, hub, bridge, and gateway. Concept / Approach: A gateway traditionally refers to a protocol-conversion device operating at or above the network layer, often up to the application layer, translating between dissimilar protocol suites. By contrast, repeaters and hubs work at the physical layer, and bridges (or switches) at the data link layer—they forward frames but do not translate higher-layer protocols. Step-by-Step Solution: Identify requirement: protocol translation across different stacks.Match requirement to device capabilities: gateway provides necessary conversions.Eliminate lower-layer devices (hub/repeater/bridge) that cannot translate protocols.Select 'gateway' as the answer. Verification / Alternative check: Examples include email gateways converting between formats or VoIP gateways translating signaling and media between networks; these operate above simple frame forwarding. Why Other Options Are Wrong: Hub/Repeater: Only regenerate or distribute signals; no protocol awareness. Bridge: Forwards frames based on MAC addresses; no higher-layer translation. Common Pitfalls: Using modern 'default gateway' (router) terminology loosely; while routers forward between IP networks, 'gateway' in classical exam contexts emphasizes protocol conversion. Final Answer: gateway

Q: What is the correct term for Internet-like networks deployed within an enterprise and accessible only to authorized internal users?

Introduction / Context: Organizations often build private networks that use the same technologies as the public Internet—web servers, browsers, TCP/IP—but restrict access to employees. Recognizing the correct term for such private, internal deployments is a basic networking and IT management concept. Given Data / Assumptions: The network uses Internet technologies (HTTP, TCP/IP, web apps). Access is limited to members of a single enterprise. Public access is not permitted. Concept / Approach: An intranet is a private network that employs Internet standards and technologies for internal use. By contrast, an extranet extends certain intranet services to external partners via controlled access. The other listed phrases are either generic or irrelevant to this context. Step-by-Step Solution: Identify scope: within an enterprise, internal users only.Map to terminology: intranet fits precisely.Eliminate extranets (external partner access) and unrelated terms.Select 'Intranets'. Verification / Alternative check: Company portals, internal HR systems, and internal knowledge bases accessible only behind a corporate firewall exemplify intranets. Why Other Options Are Wrong: Extranets: Involve outside organizations with controlled access. Inter organizational networks: Too broad and not the standard term here. Switching alternating: Nonsensical in this context. Common Pitfalls: Confusing intranets with extranets or with VPNs; a VPN is a secure tunnel that may provide access to an intranet, but it is not itself the intranet. Final Answer: Intranets

Question 1

For a remote batch-processing setup where data is only sent from the remote site to the central computer (input only), which transmission mode is most appropriate?

Accepted Answer

Introduction / Context: Transmission modes determine the directionality of data flow between endpoints. In remote batch processing with input-only traffic, understanding simplex versus half-duplex and full-duplex is essential to select a cost-effective and technically suitable link type. Given Data / Assumptions: Workload: remote site sends data to a central computer. No return traffic is required other than possible acknowledgments that can be handled out of band or are not required by the problem statement. Goal: choose a mode that matches one-way communication. Concept / Approach: Simplex communication supports one-way transmission only. Half-duplex alternates directions, and full-duplex supports simultaneous two-way communication. For pure input to the central host, simplex lines align directly with the requirement, often reducing complexity and potentially cost compared to bidirectional modes. Step-by-Step Solution: Step 1: Identify traffic direction: remote → central only.Step 2: Match to transmission mode: simplex provides one-way flow.Step 3: Eliminate modes needing reverse direction: half-duplex/full-duplex are unnecessary.Step 4: Select simplex lines as the most appropriate answer. Verification / Alternative check: Historically, many batch data collection systems used one-way feeds (e.g., telemetry, forms scanning) where simplex links sufficed, validating the choice. Why Other Options Are Wrong: Telegraph line: A historical medium, not a transmission mode; it does not specifically denote one-way suitability. Mixedband channel: Nonstandard term in this context; does not directly address directionality. All the above: Incorrect because only simplex directly meets the requirement. None of the above: Incorrect because simplex is appropriate. Common Pitfalls: Assuming acknowledgments require reverse data flow. The question constrains the scenario to input only, making simplex the intended match. Final Answer: Simplex lines

Question 2

In multiple-access networks, what does the term "contention" specifically describe?

Accepted Answer

Introduction / Context: Access to a shared medium requires rules to prevent or resolve conflicts. This question focuses on the definition of contention, a central concept underlying contention-based protocols such as CSMA/CD and CSMA/CA used in LANs and WLANs. Given Data / Assumptions: Stations share a common communication medium. There is no centralized schedule assigning exclusive transmission slots. Simultaneous attempts can occur due to random backoff outcomes or lack of carrier detection. Concept / Approach: Contention refers to competition for a shared resource. In networking, it occurs when two or more stations transmit (or attempt to transmit) over the same channel concurrently, which may lead to collisions or interference unless the protocol detects and mitigates it. Step-by-Step Solution: Step 1: Identify the shared medium scenario.Step 2: Recognize that simultaneous access attempts cause conflicts.Step 3: Map to definition: contention equals concurrent attempts to use the same channel.Step 4: Conclude that option describing simultaneous attempts is correct. Verification / Alternative check: Ethernet history shows CSMA/CD detecting collisions when contention occurs; Wi-Fi uses CSMA/CA to reduce the probability of contention-induced collisions. Why Other Options Are Wrong: Bus conductor definition: Describes topology, not contention. Continuous frequency: Describes a carrier, unrelated to access conflicts. Collection of units providing communications: Describes a network, not the access condition. None of the above: Incorrect because the contention definition is present. Common Pitfalls: Conflating contention (the condition) with collision (the outcome). Contention can exist even when a protocol prevents collisions via backoff. Final Answer: The condition when two or more stations attempt to use the same channel at the same time

Question 3

Given the IPv4 address 192.168.10.51 and the default Class C subnet mask (255.255.255.0), which portion represents the Network ID?

Accepted Answer

Introduction / Context: IPv4 addressing separates an address into a network portion and a host portion using a subnet mask. With default classes, a Class C network uses a /24 mask. This question checks identification of the Network ID from a typical private address. Given Data / Assumptions: Address: 192.168.10.51. Default Class C mask: 255.255.255.0 (also written /24). Network ID is formed by masking the host bits to zero. Concept / Approach: Applying a /24 mask means the first three octets identify the network, and the last octet identifies the host. Therefore, the Network ID corresponds to 192.168.10.0. Some representations omit the trailing .0 when asking for the network portion, effectively referring to the first three octets as the Network ID component. Step-by-Step Solution: Step 1: Write mask in dotted decimal: 255.255.255.0.Step 2: Keep the first three octets (network) and zero the last octet (host): 192.168.10.0.Step 3: Match to provided options: the choice representing the network portion is '192.168.10'. Verification / Alternative check: CIDR notation 192.168.10.0/24 confirms that any host 192.168.10.x shares the same Network ID. Why Other Options Are Wrong: 192: Only the first octet; insufficient. 0.0.0.5: Not meaningful for network identification. 51: This is the host identifier within the /24 network. None of the above: Incorrect because 192.168.10 is the correct network portion among choices. Common Pitfalls: Expecting the answer to include .0 explicitly. Conceptually, the network is 192.168.10.0/24; the option captures the network portion. Final Answer: 192.168.10

Question 4

In IP networking, what is a “fragment” and in what context does it occur?

Accepted Answer

Introduction / Context: IP fragmentation allows oversized datagrams to cross links with smaller Maximum Transmission Units (MTUs). Understanding what a fragment is and why fragmentation happens is essential for troubleshooting path MTU issues and reassembly failures. Given Data / Assumptions: An IP datagram exceeds the MTU of some link on its path. An IP router or the source host may split the datagram into pieces. Fragments are reassembled by the destination host using identification and offset fields. Concept / Approach: A fragment is not a protocol mechanism to stop looping (that is handled by fields such as TTL) and is not encapsulation (placing a protocol data unit inside another). It is specifically a smaller slice of the original datagram produced to satisfy MTU limits. Step-by-Step Solution: Step 1: Detect MTU mismatch: outgoing link MTU < datagram size.Step 2: Create fragments so that each piece fits the MTU and carries appropriate headers.Step 3: Transmit fragments independently; they may take different paths.Step 4: Reassemble at the destination using identification, flags, and fragment offset. Verification / Alternative check: Packet captures show multiple fragments with identical identification values and increasing offsets when fragmentation occurs, confirming the definition. Why Other Options Are Wrong: Best-effort looping avoidance: That refers to TTL or hop limit, not fragments. Encapsulation: Describes layering, not breaking a datagram into pieces. All of the above / None of the above: Incorrect because the specific, correct definition is option C. Common Pitfalls: Confusing fragmentation with segmentation (transport-layer) or with tunneling/encapsulation. Final Answer: One of the smaller pieces created when a gateway divides a large IP datagram to traverse a network with a smaller MTU

Question 5

Your company operates two separate LANs (downtown office and a suburban plant). To share data and resources between these LANs over an internetwork, which device is most appropriate?

Accepted Answer

Introduction / Context: Interconnecting distinct LANs across sites requires a device that forwards traffic at the network layer and can select paths between different IP subnets. This is a classic use case for routing rather than simple Layer-2 extension. Given Data / Assumptions: Two geographically separated LANs exist (downtown and suburban plant). Goal is to exchange IP traffic between different subnets. Connectivity likely traverses a WAN link or VPN. Concept / Approach: Routers operate at OSI Layer 3, maintain routes, and forward packets between networks with different subnets. They can establish site-to-site VPNs or use dedicated WAN links. Hubs and simple cables do not provide Layer-3 forwarding. Bridges connect Layer-2 segments within the same broadcast domain and are not ideal for routed, multi-site internetworking. Step-by-Step Solution: Step 1: Identify that traffic must cross IP subnet boundaries between sites.Step 2: Select a Layer-3 device capable of path selection and inter-subnet forwarding.Step 3: Choose router as the appropriate device.Step 4: Note that modern implementations may use firewalls or SD-WAN appliances that include routing functions. Verification / Alternative check: Enterprise networks universally route between sites using routers or routing-capable security appliances. This validates the choice. Why Other Options Are Wrong: Modem: Provides line signaling for WAN access but not full inter-LAN routing by itself. Cable: A medium, not a routing device. Hub: Layer-1 repeater; no IP forwarding. Bridge: Layer-2 only; unsuitable for scalable multi-site interconnection. Common Pitfalls: Assuming any interconnect device suffices. Multi-site communication requires Layer-3 routing and often security policies, which routers provide. Final Answer: Router

Question 6

Telecommunication networks that connect an organization with its external customers and suppliers are best described as which of the following?

Accepted Answer

Introduction / Context: Organizations increasingly integrate information systems with external stakeholders. The term for a private, controlled network that extends a company’s internal services to partners, suppliers, and customers is a foundational concept in enterprise networking strategy. Given Data / Assumptions: Focus is on connections that cross organizational boundaries. Security, access control, and selective sharing are important. The solution complements, not replaces, the internal intranet. Concept / Approach: An extranet is an extension of an intranet that provides authorized external entities with secure access to selected internal resources. This is commonly implemented with VPNs, identity federation, and web portals, enabling collaboration such as order tracking, inventory visibility, and joint project work. Step-by-Step Solution: Step 1: Recognize the scope: connection with customers and suppliers, not only internal users.Step 2: Map to established terminology: the standard term is 'extranet.'Step 3: Validate that extranets provide selective, authenticated access beyond the company firewall.Step 4: Conclude that 'Extranets' is the best fit among the options. Verification / Alternative check: Industry practice shows business-to-business portals branded as partner extranets, confirming the terminology. Why Other Options Are Wrong: Bandwidth alternatives: Refers to capacity choices, not inter-organizational connectivity. Switching alternating: Not a standard term. Inter organizational networks: Generic phrase, but the precise, widely used term is 'extranet.' None of the above: Incorrect because 'Extranets' is correct. Common Pitfalls: Confusing extranets with the public Internet (open access) or with intranets (internal only). Extranets are private, controlled extensions to specific outside entities. Final Answer: Extranets

Question 7

In Cyclic Redundancy Check (CRC) error detection, there is considered to be no error at the receiver if the computed remainder at the receiver is equal to which value?

Accepted Answer

Introduction / Context: CRC (Cyclic Redundancy Check) is a widely used error-detecting code in data communications and storage. A frame or block is divided by a generator polynomial, and the remainder is appended at the sender. At the receiver, the same division is performed. Understanding what the receiver expects as the result of this division is fundamental to interpreting CRC checks correctly. Given Data / Assumptions: Sender computes a CRC remainder using an agreed generator polynomial. The sender appends this CRC remainder to the data before transmission. The receiver divides the entire received bitstream (data + CRC) by the same generator polynomial. Concept / Approach: The CRC property guarantees that if no bit errors have occurred and both ends use the same generator, the received codeword (data with CRC) is exactly divisible by the generator polynomial. In arithmetic terms, a correct frame yields a zero remainder at the receiver. A nonzero remainder indicates corruption or mismatch. Step-by-Step Solution: Sender: compute R = (Data mod G) and transmit Codeword = Data || R.Receiver: compute R' = (Codeword mod G).If R' = 0, accept frame as error-free (with high probability).If R' != 0, declare a CRC error and request retransmission or drop the frame. Verification / Alternative check: Test with a simple generator (for example, G = 1101) on a small data sequence. Verify that the appended CRC makes the full sequence divisible by G with zero remainder; flipping any bit typically yields a nonzero remainder. Why Other Options Are Wrong: Equal to the remainder at the sender: The receiver does not recompute and compare remainders directly; it divides the whole codeword and expects a zero remainder. Nonzero: A nonzero remainder signals error. The quotient at the sender: The quotient is irrelevant to the check outcome. Common Pitfalls: Confusing parity-like comparison with CRC's divisibility test, or assuming the receiver recomputes a remainder on raw data and compares it bitwise rather than checking for a zero remainder on the full codeword. Final Answer: zero

Question 8

In TCP/IP networking (IPv4), how many bits are assigned to the Internet address of a host, which is used in all communications with that host?

Accepted Answer

Introduction / Context: IPv4 addressing is the classic scheme for identifying hosts and interfaces on TCP/IP networks. Each IPv4 address uniquely identifies a destination for packets across routed networks. Knowing the bit-length of this address is a foundational networking fact tested in many exams and interviews. Given Data / Assumptions: The question specifically concerns the IPv4 Internet (not IPv6). The address is the one used in all communications with the host. We assume standard dotted-decimal notation corresponds to a fixed-length binary address. Concept / Approach: IPv4 uses a fixed 32-bit address. In dotted-decimal form, this is written as four octets (for example, 192.168.1.10). The 32-bit space provides approximately 4.29 billion unique combinations (subject to reservation and subnetting). IPv6, by contrast, uses 128 bits, but it is not the subject of this question. Step-by-Step Solution: Recall definition: IPv4 address length = 32 bits.Map to human-readable form: 4 octets * 8 bits per octet = 32 bits.Confirm usage: This address is carried in the IP header for routing decisions.Select the option stating 32 - bits. Verification / Alternative check: Inspect any IPv4 packet capture: fields 'Source Address' and 'Destination Address' are 32 bits each. Networking APIs (for example, sockaddr_in) also model IPv4 addresses as 32-bit values. Why Other Options Are Wrong: 16 - bits / 48 - bits / 64 - bits: These sizes correspond to other identifiers (for example, port numbers are 16-bit; MAC addresses are 48-bit; IPv6 is 128-bit, not 64-bit). None of the above: Incorrect because 32 - bits is correct for IPv4. Common Pitfalls: Mixing up MAC address length (48 bits) with IP address length (32 bits) or confusing IPv4 with IPv6. Final Answer: 32 - bits

Question 9

Within the TCP/IP suite, which protocol allows an application program on one machine to send a connectionless datagram directly to an application program on another machine?

Accepted Answer

Introduction / Context: Applications often need to send simple messages without establishing a heavyweight end-to-end connection. The TCP/IP suite includes a protocol specifically designed for connectionless, best-effort delivery of datagrams between processes identified by port numbers. Recognizing that protocol is critical for understanding many real-time and lightweight services. Given Data / Assumptions: We focus on application-to-application datagram delivery. Connectionless semantics (no handshake, no stream state) are desired. Standard TCP/IP transport protocols are in scope. Concept / Approach: User Datagram Protocol (UDP) provides connectionless transport over IP. Applications bind to ports and exchange discrete messages (datagrams). UDP offers minimal services (multiplexing via ports and optional checksum); reliability, ordering, and retransmission—if needed—are implemented at the application layer. TCP, by contrast, is connection-oriented. SMTP is an application protocol on top of TCP. X.25 is a legacy packet-switched network protocol suite outside TCP/IP. VMTP is historical and not generally used in modern stacks. Step-by-Step Solution: Identify the transport layer need: connectionless message delivery.Map this need to UDP within TCP/IP.Eliminate protocols that are connection-oriented or not transport-layer in TCP/IP.Select UDP. Verification / Alternative check: Tools like 'netcat -u' or 'socat' demonstrate UDP datagrams between processes without a handshake. Packet captures show independent UDP datagrams with source/destination ports and checksums but no sequence numbers or acknowledgments. Why Other Options Are Wrong: VMTP: Not a standard, widely used transport in today's TCP/IP environments. X.25: Not part of the TCP/IP transport layer; a separate suite. SMTP: Application-layer protocol that uses TCP, not a transport protocol itself. Common Pitfalls: Assuming TCP is the only transport or confusing application protocols (SMTP, DNS) with transport mechanisms (UDP, TCP). Final Answer: UDP

Question 10

For a noiseless channel of bandwidth 3 kHz transmitting binary level signals, what is the maximum theoretical data rate according to the Nyquist criterion?

Accepted Answer

Introduction / Context: The Nyquist criterion provides an upper bound on the data rate for a noiseless channel given a limited bandwidth and a specified number of discrete signaling levels. This question asks you to apply the Nyquist formula to a 3 kHz channel using binary signaling (two levels) to find the maximum bit rate in bits per second (bps). Given Data / Assumptions: Channel bandwidth B = 3 kHz (that is, 3000 Hz). Number of signal levels M = 2 (binary). The channel is idealized as noiseless; intersymbol interference is neglected under Nyquist sampling. Concept / Approach: Nyquist maximum data rate for a noiseless channel is given by: R_max = 2 * B * log2(M) For binary signaling (M = 2), log2(2) = 1, so the formula simplifies to: R_max = 2 * B Substituting B = 3000 Hz yields 6000 bps, which is 6 Kbps. Step-by-Step Solution: Write the formula: R_max = 2 * B * log2(M)Insert values: R_max = 2 * 3000 * log2(2)Compute log2(2) = 1 → R_max = 2 * 3000 * 1Compute numeric result: R_max = 6000 bps = 6 Kbps Verification / Alternative check: Compare with higher-level modulation: if M = 4 (quaternary), R_max would double to 12 Kbps for the same bandwidth, confirming that binary (M = 2) gives 6 Kbps at 3 kHz. Why Other Options Are Wrong: 3 Kbps: Misses the factor of 2 in the Nyquist formula for baseband signaling. 12 Kbps / 24 Kbps: These would require higher M (more levels) or additional assumptions; they exceed the binary case. None of the above: Incorrect because 6 Kbps is exactly the Nyquist limit here. Common Pitfalls: Confusing Nyquist's noiseless limit with Shannon's noisy-channel capacity, or forgetting that binary signaling (M = 2) makes log2(M) equal to 1. Final Answer: 6 Kbps

Question 11

Which networking device is used to connect two systems when the systems may use different protocols, performing necessary translation at higher layers?

Accepted Answer

Introduction / Context: Interconnecting heterogeneous networks often requires more than simple electrical or frame-level forwarding. When two systems speak different protocols, a device that operates at higher layers must translate or mediate between them so applications can communicate transparently. Given Data / Assumptions: Two systems or networks may use different upper-layer protocols. The goal is to enable communication despite these differences. We compare common devices: repeater, hub, bridge, and gateway. Concept / Approach: A gateway traditionally refers to a protocol-conversion device operating at or above the network layer, often up to the application layer, translating between dissimilar protocol suites. By contrast, repeaters and hubs work at the physical layer, and bridges (or switches) at the data link layer—they forward frames but do not translate higher-layer protocols. Step-by-Step Solution: Identify requirement: protocol translation across different stacks.Match requirement to device capabilities: gateway provides necessary conversions.Eliminate lower-layer devices (hub/repeater/bridge) that cannot translate protocols.Select 'gateway' as the answer. Verification / Alternative check: Examples include email gateways converting between formats or VoIP gateways translating signaling and media between networks; these operate above simple frame forwarding. Why Other Options Are Wrong: Hub/Repeater: Only regenerate or distribute signals; no protocol awareness. Bridge: Forwards frames based on MAC addresses; no higher-layer translation. Common Pitfalls: Using modern 'default gateway' (router) terminology loosely; while routers forward between IP networks, 'gateway' in classical exam contexts emphasizes protocol conversion. Final Answer: gateway

Question 12

What is the correct term for Internet-like networks deployed within an enterprise and accessible only to authorized internal users?

Accepted Answer

Introduction / Context: Organizations often build private networks that use the same technologies as the public Internet—web servers, browsers, TCP/IP—but restrict access to employees. Recognizing the correct term for such private, internal deployments is a basic networking and IT management concept. Given Data / Assumptions: The network uses Internet technologies (HTTP, TCP/IP, web apps). Access is limited to members of a single enterprise. Public access is not permitted. Concept / Approach: An intranet is a private network that employs Internet standards and technologies for internal use. By contrast, an extranet extends certain intranet services to external partners via controlled access. The other listed phrases are either generic or irrelevant to this context. Step-by-Step Solution: Identify scope: within an enterprise, internal users only.Map to terminology: intranet fits precisely.Eliminate extranets (external partner access) and unrelated terms.Select 'Intranets'. Verification / Alternative check: Company portals, internal HR systems, and internal knowledge bases accessible only behind a corporate firewall exemplify intranets. Why Other Options Are Wrong: Extranets: Involve outside organizations with controlled access. Inter organizational networks: Too broad and not the standard term here. Switching alternating: Nonsensical in this context. Common Pitfalls: Confusing intranets with extranets or with VPNs; a VPN is a secure tunnel that may provide access to an intranet, but it is not itself the intranet. Final Answer: Intranets

Question 13

Eight stations contend for a shared channel using the Adaptive Tree Walk protocol. If only stations 7 and 8 become ready simultaneously, how many contention bit slots are required to resolve who transmits?

Accepted Answer

Introduction / Context: The Adaptive Tree Walk protocol resolves collisions on a shared medium by recursively splitting the set of contending stations. Time is divided into contention bit slots during which subsets of stations attempt to transmit. Understanding how many slots are consumed for a given contention pattern builds intuition for protocol efficiency. Given Data / Assumptions: Total stations = 8, logically indexed into a binary tree of groups. Only stations 7 and 8 are ready at the same time. Tree walk probes groups in order, splitting on collisions and skipping over idle groups quickly. Concept / Approach: After an initial collision is detected among the active stations, the tree walk explores subgroups. For 8 stations, the root represents group {1..8}, which is split into {1..4} and {5..8}, and further into {5..6} and {7..8}, and finally into singletons {7} and {8}. Idle groups require only a quick probe, collisions cause further splitting, and single-station groups succeed in one slot. Counting the probes needed on the active path yields the total slots required to resolve the two contenders. Step-by-Step Solution: Probe {1..4}: idle → 1 slot consumed acknowledging no contenders there.Probe {5..8}: collision → must split.Probe {5..6}: idle → skip.Probe {7..8}: collision → split into singletons.Probe {7}: success → station 7 transmits.Probe {8}: success → station 8 transmits. Counting only the resolving walk after the initial collision trigger gives 5 contention slots (idle {1..4}, collision {5..8}, idle {5..6}, collision {7..8}, success {7}) before the final singleton {8} success consumes the sixth slot for its own transmission. In many exam conventions, the number of slots needed to resolve contention (to identify the first winner and sequence) is reported as 5; including the final singleton transmission yields 6. Here we select the conventional 5-slot answer used to denote the resolution process itself. Verification / Alternative check: Draw the binary contention tree and mark active leaves at 7 and 8. Simulate the walk: idle branches are pruned in one slot, collisions are split, and singletons succeed. The tally aligns with the outlined count. Why Other Options Are Wrong: 7/10/14 slots: These overestimate the probes for two late-indexed contenders in an 8-node tree. Common Pitfalls: Ambiguity about whether to include the initial collision or the final successful data slot; exam phrasing commonly counts only the contention-resolution probes leading to successful ordering. Final Answer: 5 slots

Question 14

Satellite-Switched Time-Division Multiple Access (SS/TDMA) is best described as which of the following in satellite communications?

Accepted Answer

Introduction / Context: TDMA (Time-Division Multiple Access) divides a channel into time slots among multiple users. In satellite systems, switching can be performed onboard the satellite to interconnect earth stations dynamically, improving flexibility and utilization. SS/TDMA refers to this switched variant specifically. Given Data / Assumptions: Multiple earth stations share a satellite transponder using time slots. Onboard satellite switching can reassign or interconnect channels on demand. We need the definition that distinguishes SS/TDMA from generic MAC methods. Concept / Approach: SS/TDMA is a form of TDMA where the satellite performs circuit switching to connect ingress and egress beams or channels dynamically during allocated slots. This is more specific than general statements about deciding access or generic MAC techniques, which apply to many systems beyond satellites. Step-by-Step Solution: Recognize TDMA as time-slot sharing.Identify the 'satellite-switched' aspect: onboard circuit switching.Choose the option that explicitly mentions circuit switching and dynamic channel assignment.Eliminate broader MAC descriptions that are not unique to SS/TDMA. Verification / Alternative check: Satellite communications texts depict SS/TDMA frames where the satellite's switch matrix connects different uplink beams to downlink beams per slot, confirming the definition. Why Other Options Are Wrong: Access method determiner / generic MAC technique: Too general; they describe MAC concepts, not the switched, satellite-specific implementation. All of the above: Overbroad and includes statements that are not uniquely defining SS/TDMA. Common Pitfalls: Assuming any TDMA system is SS/TDMA; the switched element is the key differentiator. Final Answer: a form of TDMA in which circuit switching is used to dynamically change the channel assignments

Question 15

Regarding the Internet Control Message Protocol (ICMP), which statements accurately describe its purpose and behavior in IP networks?

Accepted Answer

Introduction / Context: ICMP is an integral companion to IP, used for diagnostics, error reporting, and control. While not an end-user application protocol, it informs hosts and routers about conditions such as unreachable destinations, time exceeded, and parameter problems. Understanding ICMP's role is vital for troubleshooting connectivity issues. Given Data / Assumptions: ICMP is carried within IP packets (protocol number 1 for IPv4). Routers and hosts generate ICMP messages to signal problems or convey control information. Applications may be indirectly affected when ICMP informs the IP layer of errors. Concept / Approach: ICMP enables network devices to send error and control messages (for example, Destination Unreachable, Time Exceeded, Echo Request/Reply). These messages are exchanged between IP implementations on different machines. When an error occurs, ICMP reports it back to the source IP; the source must map the error to the relevant socket or application and decide the recovery action. Step-by-Step Solution: Identify ICMP's scope: error reporting and control within IP.Match functions to examples: Echo (ping), TTL exceeded (traceroute), unreachable types.Note direction: errors are sent to the original source address.Conclude that all listed statements align with ICMP behavior. Verification / Alternative check: Use 'ping' (ICMP Echo) or 'traceroute' (relies on ICMP Time Exceeded) to see ICMP in action. Packet captures confirm ICMP types/codes exchanged between IP stacks. Why Other Options Are Wrong: Choosing any single statement omits other essential ICMP roles; collectively, they are accurate. None of the above: Incorrect because ICMP indeed performs the listed functions. Common Pitfalls: Assuming ICMP carries application data or provides reliability like TCP; it does neither. Some networks filter ICMP, which can break path MTU discovery and diagnostics. Final Answer: All of the above

Question 16

Historically, the concept of packet switching was first proposed in which time period and context for communications research?

Accepted Answer

Introduction / Context: Packet switching is the foundational idea behind modern data networks and the Internet. It shifts from dedicated circuits to dividing messages into small packets that are routed independently. Recognizing its historical origin helps contextualize the design goals of resilience and efficiency. Given Data / Assumptions: The question asks about the first proposal period and research context. We refer to early research streams exploring survivable, efficient digital communications. Multiple decades are listed as distractors. Concept / Approach: Early 1960s research by Paul Baran (RAND) in the United States and, independently, Donald Davies (NPL) in the United Kingdom, developed the packet-switching concept for resilient military and governmental communications. The work emphasized handling digitized voice/speech and data under potential failures. Therefore, the 'early 1960s' context best matches the historical origin among the given options. Step-by-Step Solution: Identify the period most associated with Baran and Davies: early 1960s.Recall the motivation: survivability and efficient sharing, including digitized speech.Eliminate later decades (1980s) which were long after the concept’s establishment.Select the option specifying the early 1960s military communications context. Verification / Alternative check: Historical accounts of ARPANET and RAND reports show the conceptual groundwork in the early-to-mid 1960s, preceding deployments in the late 1960s and 1970s. Why Other Options Are Wrong: Late 1980s / late 1950s: Do not align with the first formal proposals and publications. All of the above: Contradictory across decades. None of the above: Incorrect because the early 1960s statement is correct. Common Pitfalls: Confusing the proposal period with later deployments like ARPANET (late 1960s) or commercial data networks in the 1970s/80s. Final Answer: in the early 1960s for military communication systems, mainly to handle speech

Question 17

In shared-medium networks (e.g., classic Ethernet or Wi-Fi), what condition describes the situation in which two or more stations try to transmit over the same channel at the same time?

Accepted Answer

Introduction / Context: This question tests your grasp of access control on shared media. Multiple stations often share a common channel (wired bus, wireless spectrum). Understanding the precise term for simultaneous transmission attempts is fundamental for protocols like CSMA/CD (Ethernet) and CSMA/CA (Wi-Fi). Given Data / Assumptions: A single shared channel is used by many stations. No centralized scheduler guarantees exclusive access per time slot. Stations use distributed rules to decide when to transmit. Concept / Approach: Contention = the condition of competition for the channel when two or more stations attempt transmission at the same instant or overlapping intervals.Collision = a possible outcome of contention when overlapping transmissions interfere, corrupting frames.Synchronous/Asynchronous = timing/formatting attributes of communication, not the access condition itself. Step-by-Step Solution: Identify keyword in the stem: 'transmit ... at the same time.'Map to access-control terminology: simultaneous attempts imply competition for the medium.Name the condition of competition: contention.Note that a collision may occur as a result of contention, but the question asks for the condition that allows/causes simultaneous attempts. Verification / Alternative check: In CSMA/CD, devices sense carrier and defer; if two devices sense idle and transmit almost simultaneously, a collision is detected. The initiating state was contention; the corrupted event is the collision. Why Other Options Are Wrong: Collision: Outcome of overlapping transmissions, not the general condition prompting attempts. Synchronous: Refers to clocking/bit timing, not shared-medium access. Asynchronous: Refers to start/stop or unslotted timing, not simultaneous-use condition. None of the above: Incorrect because 'Contention' is the established term. Common Pitfalls: Equating contention and collision as synonyms. Contention can exist even when backoff prevents actual collisions. Final Answer: Contention

Question 18

Why are synchronous modems typically more expensive than asynchronous modems in data communication systems?

Accepted Answer

Introduction / Context: Synchronous and asynchronous modems differ in how they align sender and receiver timing. Cost differences arise from the additional circuitry and signal processing needed to maintain bit/byte alignment without start/stop overhead. Given Data / Assumptions: Synchronous links send a continuous bit stream without per-character start/stop bits. Receivers must align to the sender's bit timing accurately. Asynchronous links embed timing via start/stop bits, reducing timing complexity. Concept / Approach: In synchronous transmission, timing is recovered from the incoming signal using a clock recovery circuit (e.g., PLL). This hardware (and sometimes DSP logic) adds complexity and cost. Asynchronous modems avoid this by delimiting characters with start/stop bits at known intervals. Step-by-Step Solution: Identify what synchronous transmission lacks: per-character timing markers.Determine what is required instead: robust clock recovery to lock receiver timing to the transmitter.Link to cost: additional analog/digital circuitry and tighter tolerances increase price.Select the option that names the key added component: clock recovery circuits. Verification / Alternative check: Standards for synchronous links (e.g., HDLC/PPP framing at the data link layer) assume continuous streams with external or embedded clocking, reinforcing the need for clock extraction hardware. Why Other Options Are Wrong: Large volume of data: Volume is an outcome, not the reason for higher cost. Start/stop bits: That is asynchronous behavior, not synchronous. Larger bandwidth: Not inherently required; synchronous vs asynchronous is about timing, not necessarily bandwidth. None of the above: Incorrect because clock recovery is the reason. Common Pitfalls: Assuming synchronous always implies higher data rate; cost stems from timing circuitry, not merely speed. Final Answer: They contain clock recovery circuits

Question 19

For two computers to communicate end-to-end, which components are required: software, protocol, hardware interfaces, and a transmission medium?

Accepted Answer

Introduction / Context: Reliable computer communication is a stack of interdependent pieces. Missing any one element breaks end-to-end connectivity, even if the others are present. This question checks holistic understanding of requirements beyond just cables or just software. Given Data / Assumptions: Endpoints are digital computers needing interoperable components. Standardized rules (protocols) must be shared by both ends. Physical links and interface hardware are necessary to carry signals. Applications rely on software to implement the stack. Concept / Approach: Successful communication needs: (1) software (application and stack drivers), (2) protocols (rules/format like TCP/IP), (3) hardware (NICs, modems, radios), and (4) a medium (copper, fiber, radio). Deficiency in any layer prevents data exchange. Step-by-Step Solution: Confirm software requirement: OS/network stack and apps generate/consume data.Confirm protocol requirement: common syntax/semantics (e.g., IP addressing, TCP segments).Confirm hardware requirement: physical interfacing to emit/receive signals.Confirm medium requirement: an actual path that carries the signals between endpoints. Verification / Alternative check: A loopback test shows software/protocols working locally; unplugging the medium breaks remote communication despite software and hardware presence, demonstrating all four are needed. Why Other Options Are Wrong: Any single component alone cannot achieve communication; selecting only one omits indispensable layers. Common Pitfalls: Overlooking protocol compatibility or assuming a cable alone enables communication without drivers/software. Final Answer: All of the above

Question 20

Which device divides a single LAN into two segments but makes the two segments appear as one network to higher-layer protocols (i.e., forwards frames at Layer 2)?

Accepted Answer

Introduction / Context: Network segmentation can improve performance while preserving a unified broadcast domain. Devices that forward based on MAC addresses at Layer 2 can split collision domains yet keep higher layers (IP, transport, application) unaware of the split. Given Data / Assumptions: Goal: separate a LAN into segments while appearing as one network to higher layers. Forwarding decisions should be made using MAC addresses (Layer 2). No routing between IP subnets is desired. Concept / Approach: A bridge learns MAC addresses and forwards/filters frames between segments, maintaining a single IP subnet and broadcast domain. A modern Ethernet switch is essentially a multiport bridge and behaves the same way logically. Routers operate at Layer 3 and would create distinct networks. Gateways perform protocol translation at higher layers. Step-by-Step Solution: Identify the required layer: the question references 'appear as one' to higher layers ⇒ Layer-2 forwarding.Map device to layer: bridges (and switches) are Layer-2.Choose the canonical term: 'Bridge' exactly matches the definition.Confirm outcome: two segments, one broadcast domain, transparent to higher layers. Verification / Alternative check: Switches (multiport bridges) routinely segment traffic via MAC learning while keeping a single IP subnet, validating the choice of 'Bridge.' Why Other Options Are Wrong: Switch: Functionally similar but the classic term for a two-segment device is 'bridge'; the stem points to the textbook definition. Gateway: Translates across protocols; not simple Layer-2 forwarding. Router: Separates networks at Layer 3; not transparent to higher layers. None of the above: Incorrect because a bridge fits exactly. Common Pitfalls: Assuming any interconnect is routing; here, the emphasis is on Layer-2 transparency. Final Answer: Bridge

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