Computer Networks

DNS servers map hostnames to IP addresses, so hackers can use DNS data to discover a host's network location. TCP/IP, Telnet, and SSL servers don't provide this network mapping information.

Throughput measures work done per unit time (transactions/day, bytes/second, requests/minute). Options A, B, D, and E all measure completed work. Errors per hour measures failure rate, not throughput - it's a quality/reliability metric, not a productivity metric.

IP addresses have 5 classes: Class A, B, C for standard networking; Class D for multicasting; and Class E for experimental/reserved use. This is a fundamental IP addressing concept. Option C is correct.

The loopback address 127.0.0.1 is the standard IPv4 address used for testing the local network stack. It refers to the local machine and is used for diagnostics and local services. This is a fundamental networking concept. Option A is correct.

Routers operate at Layer 3 (Network Layer) of the OSI model, where they make forwarding decisions based on IP addresses. They route packets between different networks by examining destination IP addresses and using routing tables to determine the best path. Switches operate at the Data Link Layer, not routers.

Switches operate at Layer 2 (Data Link Layer) of the OSI model, using MAC addresses to forward frames within a network segment. They maintain MAC address tables to learn which devices are connected to which ports, enabling efficient frame forwarding. Routers operate at the Network Layer, not switches.

FTP is an Application Layer protocol. It provides file transfer services to end-user applications and operates at Layer 7 of the OSI model (or the Application Layer of the TCP/IP model). FTP uses TCP for reliable transport (operating at Transport Layer), but FTP itself belongs to the Application Layer.

RIP (Routing Information Protocol) is a Dynamic Routing protocol. It automatically discovers and maintains routes by exchanging routing information with neighboring routers. Routes are calculated based on hop count distance (metric). Static routing requires manual configuration, while RIP automatically adapts to network topology changes.

There are 5 classes of IP addresses in the traditional classful addressing scheme: Class A (0.0.0.0 - 127.255.255.255), Class B (128.0.0.0 - 191.255.255.255), Class C (192.0.0.0 - 223.255.255.255), Class D (224.0.0.0 - 239.255.255.255 for multicast), and Class E (240.0.0.0 - 255.255.255.255 reserved).

127.0.0.1 is the standard loopback address for IPv4. The entire 127.0.0.0/8 block is reserved for loopback, used to test the local TCP/IP stack. Sending packets to any address in this range routes them back to the local machine without leaving the host, useful for diagnostics and local services.

Routers operate at Layer 3 (Network Layer) of the OSI model, where they make forwarding decisions based on IP addresses. They route packets between different networks by examining destination IP addresses and using routing tables to determine the best path. Switches operate at the Data Link Layer, not routers.

Switches operate at Layer 2 (Data Link Layer) of the OSI model, using MAC addresses to forward frames within a network segment. They maintain MAC address tables to learn which devices are connected to which ports, enabling efficient frame forwarding. Routers operate at the Network Layer, not switches.

FTP operates at the Application Layer (Layer 7) of the OSI model. It provides file transfer services directly to user applications and uses TCP for reliable transport at lower layers.

There are 5 classes of IP addresses defined under classful addressing: Class A, B, C, D, and E. Distractors suggesting 2, 3, or 4 classes are incorrect as they omit multicast (Class D) or experimental/reserved (Class E) ranges.

The loopback address 127.0.0.1 is reserved for testing the local TCP/IP stack. Any packet sent to this address never leaves the host and loops back to the local system, useful for testing network services without actual network traffic.