Computer Networks

Step 1: Understand the evolution of Ethernet. Early Ethernet standards (like 10BASE5 and 10BASE2) used a bus topology, where all devices shared a single coaxial cable.
Step 2: Understand modern Ethernet. Contemporary Ethernet standards (like 10BASE-T, 100BASE-TX, 1000BASE-T) use a star topology. Devices are connected to a central switch or hub using twisted-pair cables. This is the dominant topology in use today.
Step 3: Evaluate the options. While legacy Ethernet used a bus, virtually all modern Ethernet installations use a star topology. In the context of a current exam, "Star" is the expected answer. Bus is historically correct but outdated.

Step 1: Define the term "protocol" in the context of computing. A protocol is a standard set of rules that allow electronic devices to communicate with each other. These rules include what data is communicated, how it's communicated, and how errors are handled.
Step 2: Analyze the other options.

(A) Resource Locator (like URL): An address for a resource on the internet, not a set of rules.
(B) Hypertext (like HTML): A system for displaying text that links to other text.
(D) Domain: A name that identifies a network or website on the internet.
The term that means "a set of rules" is a protocol. Examples include HTTP (Hypertext Transfer Protocol) and TCP/IP (Transmission Control Protocol/Internet Protocol).

Step 1: Define the characteristics of the described topology. The key feature is that all devices (nodes) connect to a single, central point (a hub or a switch).
Step 2: Compare this with the given options.

(A) Bus topology: All devices connect to a single main cable (the bus).
(B) Ring topology: Each device is connected to exactly two other devices, forming a circular pathway for signals.
(C) Star topology: All devices are connected to a central hub. This matches the description perfectly.
(D) Tree topology: A hybrid topology that combines bus and star topologies. It has a root node, and all other nodes are linked to form a hierarchy.
The topology where all devices connect to a central hub is the star topology.

In the context of computer networks, topology refers to the arrangement or layout of the various elements (links, nodes, etc.) of a computer network. It describes how the computers, printers, and other devices are connected to each other. There are two types of topology:

Physical Topology: The physical layout of the cables and devices.
Logical Topology: The way data travels through the network.
Common physical topologies include Bus, Ring, Star, Mesh, and Tree.

Transmission mode refers to the direction of signal flow between two linked devices. It specifies how data is transmitted from a sender to a receiver. There are three main types of transmission modes:

Simplex: Communication is unidirectional, like a one-way street. One device sends, the other only receives. (e.g., keyboard to computer, radio broadcast).
Half-Duplex: Each device can both send and receive, but not at the same time. It's like a walkie-talkie.
Full-Duplex: Both devices can send and receive simultaneously. It's like a telephone conversation.

A Local Area Network (LAN) is a collection of interconnected devices, such as computers, printers, and servers, that are confined to a small geographical area. This area is typically a single building, an office, a home, or a university campus. Key characteristics:

Limited Area: Operates within a restricted physical space.
High Speed: Generally offers very high data transfer rates.
Private Ownership: The network is usually privately owned and managed by the organization it serves.
Technologies like Ethernet and Wi-Fi are commonly used to build LANs.

In computing, a protocol is a set of rules and conventions that governs how data is exchanged between two or more communicating devices. It defines the syntax, semantics, and synchronization of communication. Essentially, a protocol is the "language" that devices use to talk to each other. It ensures that the sending device and receiving device understand each other. Examples include:

HTTP (Hypertext Transfer Protocol): for viewing web pages.
TCP/IP (Transmission Control Protocol/Internet Protocol): for routing data across the internet.
SMTP (Simple Mail Transfer Protocol): for sending emails.

Step 1: Define the different network types by geographical scope.

PAN (Personal Area Network): A few meters (e.g., Bluetooth).
LAN (Local Area Network): A room, building, or campus.
MAN (Metropolitan Area Network): A city.
WAN (Wide Area Network): A large geographical area (country, continent, globe).

Step 2: Match the description to the definition. A network within a building or campus fits the description of a Local Area Network (LAN).

Step 1: Define the computer network types by their geographical range.

PAN (Personal Area Network): Spans a very short distance, typically a few meters, to connect devices for a single person (e.g., connecting a mouse, keyboard, or headset via Bluetooth).
LAN (Local Area Network): Covers a limited area like a single building or a campus.
MAN (Metropolitan Area Network): Spans a city or a large town.
WAN (Wide Area Network): Covers a large geographical area, such as a country or the entire globe.

Step 2: Compare their sizes. Based on the definitions, the hierarchy of size from smallest to largest is PAN& Lt;LAN& Lt;MAN& Lt;WAN. Therefore, the Personal Area Network is the smallest.

Step 1: Recall the origin of the term "Telnet". Telnet is one of the earliest network protocols. Its name is a portmanteau.
Step 2: Break down the name. Telnet stands for Teletype Network. It was designed to allow a user to log in to a remote computer and use it as if they were sitting at a local terminal (or teletypewriter).

Step 1: Differentiate between IPv4 and IPv6. IPv4 is the older addressing system and uses 32-bit addresses. IPv6 was developed to overcome the address exhaustion of IPv4.
Step 2: State the size of an IPv6 address. An IPv6 address is 128 bits long, providing a vastly larger address space than IPv4.
Step 3: Analyze the byte options. Since 1 byte = 8 bits:

32 bytes = 256 bits.
128 bytes = 1024 bits.
These are incorrect. The correct answer is 128 bits.

Step 1: Define network edge vs. network core. The network is conceptually divided into the edge and the core.

Network Edge: Contains the end systems that users interact with, which run applications (e.g., PCs, servers, smartphones).
Network Core: Contains the interconnected routers and switches that forward data through the network.

Step 2: Classify the devices.

(B) PC, (C) Smartphone, (D) Server are all end systems, placing them at the network edge.
(A) Switch is a device that operates within the network core to connect edge devices and forward traffic between them.
Therefore, a switch is not a network edge device.

Step 1: Define the Internet. The Internet is a massive, global network that connects billions of computers and other electronic devices. It works by using standard protocols (like TCP/IP) to link together many different types of smaller networks—including private, public, academic, business, and government networks.
Step 2: Evaluate the options.

(A) Collection of WAN: While the internet involves many Wide Area Networks (WANs), this is an incomplete description. It also includes LANs, MANs, etc.
(B) Network of Networks: This is the most accurate and classic definition. It emphasizes that the Internet's primary nature is to interconnect disparate and diverse networks into a single cohesive global system.
(C) Collection of Networks: This is true but less precise than "Network of Networks". The "interconnection" aspect is key.
(D) Collection of identical LAN & MAN: The networks connected to the internet are not identical; they are highly varied.
The best description of the Internet is a "Network of Networks".

Step 1: Review the functions of the OSI layers regarding error detection.

(D) Data Link Layer (Layer 2): Uses a Frame Check Sequence (FCS), often a Cyclic Redundancy Check (CRC), to detect errors in frames.
(C) Network Layer (Layer 3): The IPv4 header includes a checksum to check for errors in the header itself.
(B) Transport Layer (Layer 4): Both TCP and UDP use checksums to verify the integrity of the header and the data payload.
(A) Session Layer (Layer 5): Its primary role is to manage, maintain, and terminate sessions (dialogues) between applications. It is not directly concerned with bit-level error detection of the data payload; that is handled by the layers below it.

Step 2: Conclude which layer does not use a checksum. Error detection via checksums is a key function of the Data Link, Network, and Transport layers. The Session layer does not operate a checksum.