2.1 Communications.networking Flashcards
What does ARPAnet stand for?
Advanced Research Projects Agency Network
What does WAN stand for, and what does it represent?
Wide Area Network; a network covering a very large geographical area.
Define LAN.
Local Area Network; a network covering a small area, such as a single building.
What is a MAN?
Metropolitan Area Network; a network larger than a LAN but smaller than a WAN, typically covering several buildings in a single city (e.g., university campus).
What is the purpose of a file server?
A server on a network where central files and data are stored, accessible by users logged onto the network.
What does a hub do in a LAN?
Connects devices in a LAN and directs incoming data packets to all devices on the network.
How does a switch differ from a hub?
A switch connects devices in a LAN but directs incoming data packets to a specific destination address only.
What is the function of a router?
Enables data packets to be routed between different networks (e.g., joining LANs to form a WAN).
What does a modem do?
Converts digital data to analog for transmission via telephone wires and vice versa for processing by a computer.
What does WLAN stand for?
Wireless Local Area Network.
What is a (W)AP?
(Wireless) Access Point; allows a device to access a LAN without a wired connection.
What is a PAN?
Personal Area Network; a network centred around a person or their workspace.
Describe a client-server network.
A network with dedicated servers and specific client workstations, where all clients connect to the servers.
What is spread spectrum technology?
Wideband radio frequency technology with a range of 30 to 50 meters.
Define a node in networking.
A device connected to a network, such as a computer, storage device, or peripheral.
What is a peer-to-peer network?
A network where each node can share files with other nodes without a central server.
What is the difference between thin and thick clients?
Thin clients depend on the internet and a powerful computer for processing, while thick clients can work offline and perform processing independently.
Describe the bus network topology.
Uses a single central cable, where all devices connect, and data travels in one direction with only one device transmitting at a time.
What is a data packet?
A message or data sent over a network containing the sender’s address, recipient’s address, and the actual data.
Explain the star network topology.
A network where all devices connect to a central hub or switch, and data packets are directed through this hub/switch.
Define the mesh network topology.
Interlinked devices that use routing logic to send data packets via the shortest route.
What is a hybrid network?
A network combining multiple topologies.
What is cloud storage?
A method of storing data on off-site servers.
Define data redundancy.
Storing the same data on multiple servers for maintenance or repair purposes.
What is Wi-Fi?
Wireless connectivity using radio waves or microwaves, implementing IEEE 802.11 protocols.
What is Bluetooth?
Wireless connectivity using radio waves in the 2.45 GHz frequency band.
Describe spread spectrum frequency hopping.
Transmitting radio signals by randomly picking one of 79 channels; switches channels if the chosen one is busy.
Define WPAN.
Wireless Personal Area Network; a local wireless network for devices in close proximity (e.g., a laptop, smartphone, printer).
What is a twisted pair cable?
A cable with two wires of a single circuit twisted together, multiple pairs form a single cable.
Describe a coaxial cable.
A cable with a central copper core, insulation, copper mesh, and outer insulation.
What is a fiber optic cable?
A cable using glass fibers and pulses of light to transmit data.
What is the role of a gateway?
Connects LANs that use different protocols.
Define a repeater in networking.
A device that boosts signals on both wired and wireless networks.
What are repeating hubs?
Hybrid devices combining hub and repeater functions.
What does a bridge do?
Connects LANs using the same protocols.
What is a softmodem?
A software-based modem using minimal hardware.
What is a NIC?
Network Interface Card; allows devices to connect to a network or the internet, associated with a MAC address.
What is a WNIC?
Wireless Network Interface Card/Controller.
Define Ethernet.
A protocol (IEEE 802.3) used by many wired LANs.
What is a conflict in networking?
A situation where two devices have the same IP address.
What does broadcast mean in networking?
Communication where data is sent from a sender to multiple receivers.
What is a collision in networking?
When two messages or data from different sources attempt to transmit along the same data channel simultaneously.
What is CSMA/CD?
Carrier Sense Multiple Access with Collision Detection; a method used to detect and resolve data collisions in a network.
What is bit streaming?
A contiguous sequence of digital bits sent over a network or the internet.
What is buffering?
Temporary storage that holds data before it is processed or transmitted.
Define bit rate.
The number of bits per second that can be transmitted over a network, measuring the data transfer rate in digital telecommunications.
What is on-demand bit streaming?
A system that allows users to stream video or music files from a central server as needed, without saving the files on their device.
Describe real-time bit streaming.
A system where an event is captured (e.g., via camera and microphone), encoded on a server, and made accessible to users live, as it happens.
What is ARPAnet, and why is it significant?
ARPAnet was an early form of packet-switching WAN (circa 1970, USA) connecting large computers in the Department of Defense. It later included university computers and developed the technical foundation for the internet.
How did local area networks (LANs) emerge?
LANs developed in the 1980s alongside personal computers and connected computers and shared devices, such as printers, within a single building.
What is the relationship between WANs and LANs?
WANs typically consist of multiple LANs connected via public communication networks, such as telephone lines or satellites.
How is a WAN different from the internet?
WANs are private networks requiring passwords and user IDs, while the internet is a decentralised network with a common access point, open to anyone with internet access.
What is a metropolitan area network (MAN)?
A MAN connects multiple smaller networks (e.g., LANs) within a limited geographical area, such as a city or a university campus.
How does the geographical scope of a WAN compare to a MAN?
A WAN covers much larger areas, such as countries or continents, while a MAN is restricted to a single city or region.
What are the benefits of networking devices and computers?
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- Shared devices, such as printers, reduce costs.
- Software licenses for networks are cheaper than for stand-alone computers.
- Users can share files and data.
- Reliable data access from a central source, such as a file server.
- Centralised backup of data and files.
- Communication via email and instant messaging.
- Network managers can oversee access rights and restrict external access.
What are the drawbacks of networking devices and computers?
- High initial costs for cabling and servers.
- Managing large networks can be complex and challenging.
- Device breakdowns, such as file server failures, can impact the entire network.
- Malware and hacking risks, especially for LANs connected to larger WANs, though firewalls offer some protection.
What infrastructure components enable networked computers to communicate?
- Hardware: LAN cards, routers, switches, wireless routers, cabling.
- Software: Network operation and management, firewalls, security applications/utilities.
- Services: DSL, satellite communication channels, wireless protocols, IP addressing.
How are private networks defined?
Private networks are owned by a single company or organization. They often consist of LANs or intranets with restricted user access requiring passwords and user IDs. Companies are responsible for equipment, software, maintenance, and staff training.
What characterises public networks?
Public networks are owned by communication carrier companies, such as telecoms providers. They are used by multiple organizations, often without specific password requirements, though sub-networks may have security measures.
What is a LAN, in more detail?
A Local Area Network (LAN) is contained within one building or a small geographical area. It connects computers and devices (e.g., printers) through hubs or switches, with at least one hub or switch connected to a router or modem for internet access or integration into a WAN.
Define a Wireless LAN (WLAN).
A WLAN provides wireless network communications over short distances (up to 100 meters) using radio or infrared signals instead of cables.
What are wireless access points (WAPs)?
WAPs are devices connected to the wired network at fixed locations, enabling WLAN connectivity. They transmit data between the WLAN and the wired network.
Why do commercial WLANs require multiple WAPs?
Due to the limited range of wireless signals (up to 100 meters for radio and 1-2 meters for infrared), multiple WAPs ensure uninterrupted wireless communication over larger areas.
What technologies do WAPs use?
Spread Spectrum Technology: Wideband radio frequency with a range of a few meters to 100 meters.
Infrared: Very short range (1-2 meters), easily blocked, and of limited use.
How do end users access WLANs?
Through wireless LAN adapters, either built into devices or as plug-in modules.
What is the approximate size range of a WAN, MAN, LAN, and PAN?
- WAN (Wide Area Network): 100 km to over 1000 km.
- MAN (Metropolitan Area Network): 1 km to 100 km.
- LAN (Local Area Network): 10 m to 1000 m.
- PAN (Personal Area Network): 1 m to 10 m (typically a home system)
What is the client-server networking model?
A model where dedicated servers manage files, security, and shared resources, and client workstations connect to the servers.
What are key features of the client-server model?
- Most files are stored on dedicated servers, accessible by users.
- Central security databases control access using passwords and user IDs.
- Allows installation of software on client computers.
- Offers scalability and centralised backup systems.
- Provides access control and better security than peer-to-peer networks.
- Central servers manage email storage, delivery, and sending.
What is the role of a file server in a client-server network?
- Central storage and management of data files.
- Enables file sharing without offline devices like memory sticks.
- Can be configured as a host machine, allowing remote access to storage as if it were local.
What are advantages of the client-server model over peer-to-peer networks?
- Greater scalability.
- Centralised security and resource control.
- Reliable data backup and recovery.
- Better stability and support for large user bases.
What is a potential drawback of the client-server model?
Bottlenecks can occur if multiple client requests are made simultaneously.
When is the client-server model typically used?
- For large user bases or small groups needing data sharing.
- When access to network resources must be controlled.
- When strong network security is required.
- To ensure data is protected from accidental loss through centralised backups.
Provide an example of a client-server model in use.
Amazon uses a client-server network model for order processing, billing, and data security. Each user experiences a unique front-end without interaction with other users.
What is the primary difference between the client-server and peer-to-peer models?
In the client-server model, sharing of data is the most important aspect, while in the peer-to-peer model, connectivity is the primary focus.
What is the primary structure of a peer-to-peer network?
A network model where each node can share its files with all others, acts as both supplier and consumer of resources, and there is no central server.
How do services work in a peer-to-peer network?
- Services available on the network are listed on a designated “look-up” computer.
- Nodes contact the “look-up” computer to locate the required services from other nodes.
What is a key difference between peer-to-peer and client-server models?
In peer-to-peer networks, peers are equal participants, sharing resources and responsibilities, while in the client-server model, consumers and resources are separated, and servers manage resources centrally.
What are the limitations of peer-to-peer networks?
- No central storage or authentication, leading to limited data security.
- Performance and management issues arise with more than 10 nodes.
- No robust security system, making it unclear who is authorised to share certain data.
What are the advantages of peer-to-peer networks?
- Simple setup for small networks (10 or fewer nodes).
- Allows nodes to share resources and communicate directly.
- No need for a central server or complex infrastructure.
In what scenarios is a peer-to-peer network ideal?
- Small networks with minimal security needs.
- Situations requiring workstation-based applications.
- Frequent interaction among users, such as small businesses or workgroups.
Provide an example of a peer-to-peer network use case.
A small business like a builder and five associated workers needing access to each other’s schedules, past jobs, and skills without requiring robust security or central servers.
Why is there limited security in peer-to-peer networks?
Because there is no central security system or authentication procedures, users rely on their own node’s share point for control.
What is a thin client in the client-server model?
A thin client is a device or software that relies heavily on a server for processing and access to files, requiring a constant connection to function. Examples include web browsers and POS terminals.
What is a thick client in the client-server model?
A thick client is a device or software capable of functioning both offline and online, using local resources like storage and RAM for processing. Examples include PCs and offline computer games.
What are the advantages of thin clients?
- Less expensive to expand (uses low-powered, cheap devices).
- Centralised data updates and software installations.
- Server-based protection against hacking and malware.
What are the disadvantages of thin clients?
- High reliance on the server; devices fail if the server or connection is down.
- Higher start-up costs compared to thick clients despite cheaper hardware.
What are the advantages of thick clients?
- More robust; can process tasks even without a server connection.
- Clients have more control over programs and data/files.
What are the disadvantages of thick clients?
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- Less secure; clients manage their own data security.
- Data and software must be updated individually on each client.
- Potential data integrity issues from inconsistent updates among clients.
What are the key features of thin client software?
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- Requires a constant connection to a remote server to function.
- Uses minimal local resources like SSD or RAM.
- Relies on a fast, stable network connection.
- Data is stored remotely on a server.
What are the key features of thick client software?
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- Can run some features offline without a server connection.
- Relies on local resources like SSD, RAM, or CPU for processing.
- Tolerant of slower network connections.
- Stores data locally on resources like HDD or SSD.
Compare the cost structure of thin and thick clients.
Thin clients have cheaper hardware but higher start-up costs due to server reliance, whereas thick clients have higher individual hardware costs but no need for a robust server infrastructure.
Why might a company choose thin clients over thick clients?
Thin clients are preferable for centralised management, lower hardware costs, and enhanced security managed through the server.
In what situation would thick clients be more suitable?
Thick clients are better for environments where offline functionality is critical and users need direct control over their data and programs.
What is a bus network topology? Its feature?
A bus network uses a single central cable to which all devices are connected, with data traveling in one direction. Terminators at each end prevent signal reflection.
What are the advantages of a bus network?
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- Easy to expand by adding nodes.
- If one node fails, the rest of the network continues to function.
What are the disadvantages of a bus network?
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- The entire network fails if the main cable breaks.
- Performance deteriorates under heavy traffic.
- Low security, as packets pass through every node.
When is a bus network most suitable?
For small-scale environments with light traffic, such as small offices.
What is a star network topology?
A star network uses a central hub or switch, with each device having a dedicated connection to the hub. Data is directed through this central node.
What are the advantages of a star network?
- Greatly reduced data collisions.
- High security, as packets travel only to nodes with matching addresses.
- Easy to upgrade by replacing the hub.
- Failure of a single connection affects only that node.
What are the disadvantages of a star network?
- High initial installation costs.
- Entire network fails if the central hub/switch malfunctions.
What is the difference between using a hub and a switch in a star network?
Hub: Broadcasts packets to all devices; less secure.
Switch: Sends packets only to intended recipients; more secure.
When is a star network ideal?
For networks with heavy data traffic and frequent device changes.
What is a mesh network topology? How does it transmit data between nodes?
A mesh network connects nodes directly and dynamically, using either routing (directed paths) or flooding (sending data through all nodes).
What are the advantages of a mesh network?
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- Faults are easily identified, and broken links don’t affect other nodes.
- High privacy and security due to dedicated routes.
- Easy to expand the network.
What are the disadvantages of a mesh network?
- Expensive and time-consuming due to extensive cabling.
- Complex to set up and maintain.
What are common applications of mesh networks?
- The internet, WANs, and MANs.
- Industrial and medical monitoring systems.
- Vehicle component connectivity and home electronics systems.
What is the difference between routing and flooding in mesh networks?
Routing: Uses logic to find the shortest route and reroutes around failures.
Flooding: Sends data to all nodes, potentially causing network congestion.
What is a hybrid network?
A hybrid network combines elements of different topologies (e.g., bus, star, or mesh) to create a tailored network structure.
Why are hybrid networks used?
They leverage the strengths of multiple topologies to meet specific needs, balancing performance, cost, and scalability.
What are the advantages of hybrid networks?
- Handles large volumes of traffic.
- Easy fault identification.
- Well-suited for creating larger networks.
- Allows seamless integration of different existing network types.
What is a disadvantage of hybrid networks?
They are complex to install, configure, and maintain.
What is an example of hybrid network use?
A company integrating three hotel chains using bus, star, and mesh networks into a single hybrid network while maintaining their individual setups and allowing easy expansion.
What is cloud storage?
Cloud storage is the storage of data on offsite servers, managed by hosting companies, providing redundancy and accessibility.
What is data redundancy in cloud storage?
Data redundancy involves storing the same data on multiple servers to ensure access during maintenance or repair.
What are the types of cloud computing?
Public Cloud: Storage where the provider and client are separate entities.
Private Cloud: Dedicated storage behind a company firewall, integrating client and provider.
Hybrid Cloud: Combines private and public clouds, with sensitive data in private storage and other data in public storage.
What are the advantages of cloud storage?
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- Access files from any device globally with an internet connection.
- Eliminates the need for physical storage devices.
- Provides remote backup for disaster recovery.
- Recovers data in case of local hard disk or backup failure.
- Offers nearly unlimited storage capacity.
What are the disadvantages of cloud storage?
- Issues with accessing data if internet is slow or unstable.
- High costs for large storage capacity.
- Expensive data transfer limits from ISPs.
- Risk of losing backup data if the cloud storage company fails.
How does a hybrid cloud function?
A hybrid cloud stores sensitive data in a private cloud while using a public cloud for less sensitive data.
What concerns arise when companies use cloud storage for vast amounts of confidential data?
Concerns include:
- Physical security of the building housing the data.
- Resistance to natural disasters or power cuts.
- Safeguards regarding personnel accessing confidential data for monetary purposes.
What risks are associated with data loss in cloud storage?
Risks include:
- Actions by hackers, such as pharming attacks.
- Loss or corruption of data due to insufficient safeguards.
- Potential breaches, such as:
1. XEN hypervisor security threat forcing server reboots.
2. Data loss during routine back-up by cloud providers.
3. Celebrity photos hacking scandal exposing private data.
4. The 2016 breach of Mexico’s voter database involving Amazon cloud servers.
What is a hypervisor in cloud computing?
A hypervisor is software, firmware, or hardware that creates and manages virtual machines.
What are cloud software services?
These are software applications hosted and managed by cloud providers, including maintenance, upgrades, and security, accessed via the internet for a monthly fee.
How do cloud software applications differ from web-based apps?
Cloud software can perform tasks on a local device and store data locally if the internet connection is lost, syncing data later. Web-based apps require a constant internet connection.
What are the main advantages of cloud software applications?
- Fully tested software hosted by the provider.
- No need to install on the user’s device.
- Usable offline, with data syncing when the internet is restored.
What is the primary function of a cloud services supplier in providing software?
To connect users to required software applications, ensuring hosting, maintenance, upgrades, and security.
What is Bluetooth and how does it work?
Bluetooth is a wireless communication technology that uses 79 frequency channels centred on 2.45 GHz. Devices connect automatically, using spread spectrum frequency hopping, where communication pairs constantly change channels several times per second to minimise interference. Bluetooth supports secure wireless personal area networks (WPANs) with key encryption.
What are the primary uses of Bluetooth?
Bluetooth is useful for:
- Transferring data between devices less than 30 metres apart.
- Applications where data transmission speed is not critical.
- Low bandwidth tasks (e.g., sending music files from a phone to a headset).
How does Wi-Fi compare to Bluetooth?
Wi-Fi is suited for full-scale networks due to:
- Faster data transfer rates.
- Better range (up to 100 metres).
- Better security. Wi-Fi uses spread spectrum technology and supports wireless access at WAPs or hotspots.
What types of electromagnetic radiation are used in wireless communication?
Wireless communication uses radio waves, microwaves, or infrared. Their characteristics include:
Bandwidth: Infrared > Microwaves > Radio waves.
Penetration: Radio waves > Microwaves > Infrared.
Attenuation: Radio waves > Microwaves > Infrared.
What is the relationship between frequency and wavelength in electromagnetic waves?
The relationship is given by 𝑓=𝑐/𝜆, where: 𝑓 = frequency (Hz), 𝜆 = wavelength (m), 𝑐 = speed of light (3*10⁸m/s)
Why is infrared suitable for indoor use only?
Infrared has low penetration and high attenuation, meaning:
- Signals are blocked by walls, which prevents interference.
- Infrared is affected by rain or internal walls, limiting its range.
Why are microwaves considered a good compromise for wireless communication?
Microwaves offer reasonable bandwidth, penetration, and attenuation, making them effective for many applications.
Why can’t radio waves and microwaves transmit data globally?
The curvature of the Earth prevents short-distance electromagnetic waves from global data transmission.
How does satellite technology overcome the limitations of short-distance electromagnetic waves?
Satellites use radio waves and microwaves for communication between antennae and satellites, enabling global data transmission through the use of different frequency bands to avoid interference.
What is attenuation in wireless communication?
Attenuation refers to the reduction in amplitude of a signal, impacting its strength over distance. Radio waves have the least attenuation, making them better for long-distance transmission.
What are the three main types of cables used in wired networks? Describe them.
The three main types are:
- Twisted pair cables: Common in LANs, cheapest, low data transfer rate, most affected by external interference.
Types: Unshielded (residential) and shielded (commercial). - Coaxial cables: Common in MANs and cable TV; higher cost, better data transfer rate, less interference, but high signal attenuation.
- Fibre optic cables: Best for long distances, highest data transfer rate, least signal attenuation, highly resistant to interference, but expensive.
What is the main difference between unshielded and shielded twisted pair cables?
Unshielded cables are used by residential users and lack protection against interference. Shielded cables have a thin metal foil jacket that reduces external interference, making them suitable for commercial use.
What are the advantages and disadvantages of coaxial cables?
Advantages:
- Better data transfer rate than twisted pair cables.
- Less affected by external interference.
- Excellent anti-jamming capabilities.
Disadvantages:
- High signal attenuation.
- Higher cost than twisted pair cables.
How do fibre optic cables transmit data, and what are their key features?
Fibre optic cables transmit data using pulses of light, not electricity. Key features:
- Best data transfer rate.
- Minimal signal attenuation.
- High resistance to external interference.
- Transmission capacity is 26,000 times that of twisted pair cables.
What are the two types of fibre optic cables, and when are they used?
- Single-mode: Smaller core, less light reflection, faster and further data travel. Suitable for CATV and telecommunications.
- Multi-mode: Larger core, more light reflections, best for short distances (e.g., LANs).
What are the advantages of wireless networking?
- Easier to expand networks without cables.
- Increased device mobility (within range of WAPs).
- No cable-related tripping hazards or fire risks.
What are the disadvantages of wireless networking?
- Increased chance of external interference.
- Less secure; data can be intercepted more easily.
- Slower data transmission rates compared to wired.
- Signal strength can vary or be blocked by thick walls.
What are the advantages of wired networking?
- More reliable and stable connections.
- Faster data transfer rates without dead spots.
- Cheaper overall, despite cable installation costs.
What are the disadvantages of wired networking?
- Devices lack mobility; cables restrict placement.
- Potential tripping hazards and overheating risks.
- Risk of cable disconnections during cleaning.
What additional factors should be considered when choosing between wired and wireless networking?
- Wireless compatibility for mobile phones and tablets (e.g., Wi-Fi or Bluetooth).
- Legal regulations on wireless transmission frequencies.
- Permissions for laying underground cables.
- Competing wireless signals in the area.
What is a hub, and what is its function in a network?
A hub is a hardware device used to connect multiple devices or computers to form a LAN (e.g., a star network).
Function: Receives data packets at one port and sends them to all devices in the network.
Limitations:
Not secure for data distribution.
Wasteful of bandwidth.
What is the difference between a hub and a switch?
Hub: Sends data packets to all devices in the network, regardless of destination.
Switch: Checks data packets and sends them only to the intended recipient(s) based on the destination MAC address.
Result: Switches are more secure and efficient than hubs.
What is a MAC address, and how is it used by a switch?
A MAC (Media Access Control) address is a unique identifier for each device or computer on a network.
Switches use MAC addresses to identify:
- The source of the data packet.
- The destination device(s) for the data.
What does a repeater do?
A repeater amplifies signals to counteract attenuation (signal loss) over long distances.
Works on both:
- Analogue communication (copper cables).
- Digital communication (fibre optic cables).
What is attenuation, and how do repeaters address it?
Attenuation is the reduction in signal strength over long distances.
Solution: Repeaters boost and amplify signals, allowing them to travel further.
Can hubs and switches be wireless devices?
Yes, both hubs and switches can be either wired or wireless.
How can repeaters be used in wireless systems?
Wireless repeaters boost signals to eliminate ‘dead spots’ in the Wi-Fi zone.
Plugs into electric sockets and sends out booster signals.
Non-logical devices: Boost all detected signals indiscriminately.
What are repeating hubs, and what are their drawbacks?
Repeating hubs are hubs containing repeaters, boosting all signals before sending them to all devices.
Drawbacks:
- Single collision domain: Collisions are not resolved immediately, reducing performance.
- Unmanaged devices: Cannot manage delivery paths or network security.
What is a bridge, and what is its function in a network?
A bridge connects one LAN to another LAN using the same protocol.
Used to:
- Connect parts of a LAN to function as a single LAN.
- Prevent flooding of networks with unnecessary traffic.
Note: Bridges are wired or wireless devices.
What is the main difference between a bridge and a router?
- Bridge: Connects LANs with the same protocol.
- Router: Routes data between different networks and converts protocols for communication.
What are the main roles of a router?
- Restricts broadcasts to a LAN.
- Acts as a default gateway.
- Performs protocol translation (e.g., Ethernet to Wi-Fi).
- Moves data between networks.
- Calculates the best route to a network destination.
How do broadband routers enhance network security?
Broadband routers sit behind a firewall, which:
- Protects the network’s computers.
- Ensures data transmitted between networks - follows security protocols
How does a router deliver data packets to the correct device in a network?
- Inspects the data packet’s destination IP address.
- Sends the packet to the appropriate switch.
- The switch delivers it using the MAC destination address.
- If the MAC address doesn’t match any device, the packet is passed to another switch.
What is the primary function of a gateway in a network?
A gateway acts as an entrance point to another network, connecting dissimilar LANs by converting data packets from one protocol to another.
What additional roles can gateways perform in a network?
Gateways can also function as routers, firewalls, or servers, allowing traffic to flow in and out of networks.
How does a gateway differ from a router?
- Gateway: Converts data packets between different protocols; serves as an entry/exit point for networks but does not support dynamic routing.
- Router: Forwards data packets between networks and supports dynamic routing for flexible data forwarding.
Why are modems necessary in networking?
Modems allow digital data to be transmitted over analogue communication channels by:
- Converting digital data to analogue (modulation).
- Converting received analogue data back to digital (demodulation).
What are wireless modems, and how do they operate?
Wireless modems transmit data in a modulated form, enabling multiple simultaneous wireless communications without interference.
What is the relationship between a modem and a router in a home network?
- Modem: Connects to external networks (e.g., the internet).
- Router: Creates a local network and distributes the internet connection.
Combined devices integrate both functions into a single unit.
What is a softmodem, in more detail?
A softmodem (software modem) uses minimal hardware and relies on software running on the host computer, using the computer’s processor and RAM to replace traditional modem hardware.
What are some key features of routers?
- Forward packets of data between networks.
- Route traffic to different networks or connect LANs to the internet.
- Support dynamic routing for flexible data forwarding.
What are the limitations of gateways compared to routers?
Gateways do not support dynamic routing and are primarily used for protocol conversion rather than packet forwarding.
What is the role of a Network Interface Card (NIC)?
A NIC allows a device to connect to a network (e.g., the internet) and frequently contains the MAC address generated during manufacturing.
How does a Wireless Network Interface Card/Controller (WNIC) function?
A WNIC connects devices to the internet or networks using an antenna to communicate via microwaves. It operates in two modes:
- Infrastructure mode: Requires WAPs (Wireless Access Points) for data transfer.
- Ad hoc mode: Allows devices to connect directly without WAPs.
What layers of the OSI model do NICs and WNICs work on?
They work on layers 1 (Physical Layer) and 2 (Data Link Layer).
What is Ethernet and its IEEE designation?
Ethernet is a protocol used in wired LANs, also known as IEEE 802.3.
What are the components of an Ethernet network?
- Node: Any device on the LAN.
- Medium: The path (e.g., Ethernet cable) used by LAN devices.
- Frame: Data transmitted in frames containing source and destination MAC addresses.
What is an IP address conflict, and how can it occur?
IP address conflict happens when devices on the same network are assigned the same IP address. This often occurs when dynamic IP addresses overlap with static IP addresses.
How can IP address conflicts be resolved?
Restarting the router reassigns dynamic IP addresses, potentially resolving the conflict.
What is a collision in Ethernet networks?
A collision occurs when two messages are sent simultaneously on the same data channel, leading to interference.
How does Ethernet handle collisions?
Using Carrier Sense Multiple Access with Collision Detection (CSMA/CD):
Detects a collision by monitoring voltage changes.
Stops frame transmission and sends a ‘jam’ signal.
Waits for a random time interval before resending the frame.
What is the function of transmission counters in CSMA/CD?
Transmission counters track how many collision detection routines have been entered, with a defined limit as part of the CSMA/CD protocol.
What is bit streaming?
Bit streaming is a contiguous sequence of digital bits sent over the internet or a network, requiring high-speed communication (e.g., fast broadband).
Why is data compression necessary for bit streaming?
Bit streaming often involves large files, such as videos, which require data compression to reduce transmission size and improve efficiency.
What is the purpose of buffering in bit streaming?
Buffering ensures smooth playback by temporarily storing data and regulating the bit rate sent to the media player.
What determines the effectiveness of a buffer in bit streaming?
The effectiveness is determined by the transmission rate from the server to the buffer, which must exceed the rate from the buffer to the media player.
What are the “low water mark” and “high water mark” in buffering?
- Low water mark: Minimum data threshold in the buffer.
- High water mark: Maximum data threshold in the buffer.
What are the advantages of bit streaming?
- Immediate playback without downloading the entire file.
- No need to store large files locally.
- On-demand playback for videos/music.
- No specialist hardware required.
- Protection against piracy (harder to copy streamed files).
What are the disadvantages of bit streaming?
- Requires an active broadband connection.
- Playback pauses if the buffer capacity or broadband speed is insufficient.
- High bandwidth usage.
- Security risks associated with downloads.
- Copyright issues.
What is on-demand bit streaming?
In on-demand streaming:
- Digital files are encoded and uploaded to a server.
- A link to the file is provided on a web server.
- Users can stream files as needed, with options to pause, rewind, or fast-forward.
What is real-time bit streaming?
In real-time streaming:
- Events are captured live using cameras and microphones.
- The video signal is encoded into a streaming media file.
- The encoded file is uploaded to a video streaming server.
- The server broadcasts the live stream to the user’s device.
What is the main difference between on-demand and real-time bit streaming?
On-demand: Files are pre-recorded and allow pausing, rewinding, or fast-forwarding.
Real-time: Broadcasts live events without options to pause, rewind, or fast-forward.
