1.3.3 Networks Flashcards
What are the two types of networks and topology?
- Local Area Networks are spread over a small geographical area or single site.
- Wide Area Networks are spread over a large geographical area or multiple sites.
- Physical topologies show the physical layout of wires and components.
- Logical topologies show the layout of data flow.
What are the benefits and downsides of a bus topology?
- Inexpensive, and does not require additional hardware.
- Single point of failure in the backbone, poor performance with high traffic, no privacy as all can see data flowing.
What are the benefits and downsides of a star topology?
- Consistent performance, faster transmissions, easy to upgrade, no data collisions.
- More expensive to cable, single point of failure in the switch.
What are the benefits and downsides of a mesh topology?
- No cable cost if wireless, reliable and fast, easy to add nodes, no central switch.
- Very expensive, very especially if cabled. Difficult to maintain.
What are commonly used networking protocols?
- HTTP for web page rendering, HTTPS is encrypted.
- TCP/IP used for routing packets through networks.
- POP3 and IMAP used to send emails and access them. (POP3 deletes mail from server on view).
- FTP is used for file transmissions.
What do the application and transport layers of the TCP/IP stack do?
- Application layer is responsible for specifying the protocols in use, related to what is being sent.
- Transport layer opens a connection with TCP, splits the data into labeled packets, and requests retransmissions of any that are lost.
What do the network and link layers of the TCP/IP stack do?
- Network layer adds source/destination IP addresses and a port number, as packets are sent through routers.
- Link layer adds the MAC addresses to identify source and destination NICs for the packets to be sent to.
How does the Domain Name System work?
- URLs are easier to remember than IP, so we use them in browsers.
- Browsers send a request to a DNS server to find the IP matching the URL.
- If it is not found, a server up the hierarchy is checked.
- Once the IP is found, it is sent back to the browser so they can access the site.
What does a data packet consist of?
- A header containing sender/recipient IPs, protocols, packet order and the time until packet expiry.
- A payload containing the raw data.
- A trailer containing a checksum or cyclic redundancy check.
How does circuit switching work, and what are its advantages and disadvantages?
- Maintains a direct, open link between two devices.
- Data arrives in a logical order, and allows calls to occur without delays.
- Bandwidth is wasted, electrical interference causes corruption, and both devices must transfer data at the same rate.
How does packet switching work, and what are its advantages and disadvantages?
- Packets of data are sent between networks, along the most efficient route.
- Checksums/CRCs ensure data intactness. Multiple routes can be used, and packets can be sent far for global communication.
- Time is wasted constructing and deconstructing data, and all packets must arrive before data can be used.
How do firewalls and packet switching protect networks?
- Firewalls can be physical or virtual. Physically, they consist of two NICs, scanning packets and comparing them against packet filters.
- These predetermined rules then lead to the accepting, dropping, or rejecting of the packet. A sender will not know if a packet is dropped.
How do proxies and encryption protect networks?
- Proxy servers act as intermediaries, allowing anonymity and security, and can hold their own cache.
- Encryption keeps data secure and makes intercepted communications unreadable.
How do trojans, worms and viruses harm computers?
- Viruses are pieces of malware dependent on a host file to run to spread, capable of self-replication, infecting files it comes into contact with in memory.
- Worms are a subclass of virus, that come without the need for host files, spreading themselves, slowing down computers and networks.
- Trojans hide inside seemingly useful files, then release a payload once installed, creating backdoors or stealing information. They cannot replicate.
What hardware is used in network communication?
- NICs are required for devices to form connections, storing a unique 48-bit 12-digit hex code.
- Switches direct the flow of data in a network.
- Routers connect networks and direct traffic between them.
- Gateways are used to translate protocols when they are different between networks.
