9.2 Networking Flashcards
what is a physical network topology?
refers to the actual architecture of a network. There are two types: star and bus.
How does the physical star network topology work?
Each client has its own connection to the central hub. The hub receives packets for all the clients and delivers them to the correct recipient.
What are the advantages of physical star network topology?
(A) Packets are sent directly to their recipient so other clients on the network cannot see packets that aren’t intended for them.
(A) It is easy to add and remove clients from the network.
(A) The failure of one cable does not affect the performance of the rest of the network.
(A) no data collisions as each cable has just one device communicating over it
what are the disadvantages of the physical star network topology?
All communication over the network is stopped if the central hub fails.
Expensive to instal due to amount of cable required.
How does a physical bus topology work?
Connects clients to a single cable called a backbone. A device called a terminator is placed either end of the backbone.
What are the advantages of physical bus topology?
(A) there is not central hub reducing the chances of network failure
(A) Inexpensive to install as no need for a hub and low amount of cables
What are the disadvantages of physical bus topology?
(D) Data is sent through a shared backbone allowing every client on the network to see data that isn’t intended for them.
(D) The backbone has multiple clients which introduces the risk of collisions.
(D) if the backbone fails the entire network becomes unusable.
what is the difference between a logical bus and star network?
Bus - delivers packets to all clients on the network
Star - Delivers packets only to their recipient
Why are network topologies usually mixed?
If a network is set up as physical star it can still behave as a logical bus. Running a bus protocol on the hub allows it to distribute packets to all of the connected clients so as to act like a bus network
How does client-server networking work?
One or more central servers provide services to the clients on the network. Servers are connected to the network in the same way as clients. The servers are often more powerful than clients. the clients request services from the servers which respond with the requested service.
What are the advantages of a client-server model?
Allow for central management of clients on the network.
Can improve network security
What are the disadvantages of a client-server model?
Require high expertise to set up and manage.
How does peer-to-peer networking work?
Do not use a shared server
Services are provided by the clients themselves
Ever client has equal status. All of the clients which provide services must be running for the network to be fully operational.
What are the disadvantages of a peer-to-peer network?
All of the clients which provide services must be running in order for the network to be fully operational.
What are the advantages of peer-to-peer networking?
More cost effective as no need for a powerful server
Easier to set up and maintain than client-server networks
What’s the main benefit of wireless networking?
It allows clients to communicate within a network without being physically connected to it.
What are the disadvantages to a wireless network?
Requires a wireless access point which connects to a wired network just like any other client would.
requires a wireless network adapter in the device that connects to the wireless network
What is WIFI?
A wireless local area network that is based on international standards. It allows a device made in one part of the world to connect seamlessly to wireless networks all over the world
What are the 3 ways of keeping WiFi secure?
Encrypting transmitted data using WPA or WPA2, disabling SSID and setting up a MAC address filter
How does WPA keep a network secure?
WPA stands for WiFi protected access and requires that a new wireless client enters a password in order to connect to the network.
How can disabling SSID broadcast keep a wireless network secure?
SSID stands for service set identifier and is the name that identifies a wireless network. Disabling SSID broadcast stops wireless devices within range of the network from displaying that the network is available, only allowing those who know the SSID to connect.
How can setting up MAC address filtering keep a wireless network secure?
MAC (media access control) addresses are assigned to every wireless device by their manufacturer and are unique to that device. MAC address whitelists can be created to allow only specific devices to connect to a network. MAC address blacklists can be used to block specific devices from connecting to a network
What does CSMA/CA stand for?
Carrier sense multiple access with collision avoidance.
What is CSMA/CA?
A protocol used in wireless networks to avoid data collisions caused by multiple devices communicating simultaneously.
How does the CSMA/CA protocol work?
When a device is ready to transmit, it listens to its communication channel to check whether it is idle. If so then the data is transmitted. If the channel is busy the device waits for a random period of time before checking the channel again. An exponential backoff algorithm can be used to increase the time period for which the device waits with each check of the channel.
What is the main drawback to the CSMA/CA protocol?
Hidden nodes: when the device checking for an idle channel cannot “see” some parts of the network on which communication may be occurring.
How do you get around the hidden nodes problem in the CSMA/CA protocol?
A protocol called request to send/clear to send (RTS/CTS) is used.
How does the request to send / clear to send (RTS/CTS) protocol work?
Adds an additional step into the CSMA process
Once the transmitting device has checked whether the channel is idle it sends a “request to send” message to the server. If the server is clear it will respond with “clear to send” message meaning the device can communicate with the server
If no “clear to send” message is received the server is busy communicating with a hidden node and the transmitting device must wait before starting the CSMA process again.
