Networking Flashcards
Topologies etc. (17 cards)
Topologies
Refers to the different arrangements of connected computers and devices
Bus topology
Has one backbone, that connects every device, as they sit at different points along it. Data is sent with a MAC address, specific for each device on it’s NIC. This way all devices ignore data unless it has there MAC address with it.
Bus topology collisions
When multiple signals are sent at the same time, they can interfere with each other on the backbone, if this happens, both signals wait a random amount of time, before resending them.
Bus topology security and reliability
Has low security, as every device has to read the data to see if their MAC address is included, this means data must be encrypted. It can be unreliable, as if the main backbone cable breaks, the whole network is down.
Star topology
Every device is connected via a hub or switch in the centre.
Star topology hub
When the hub receives a signal, it sends it to all of its connections. This is lower in security, as every device reads every message, looking for a MAC address. It’s also slower.
Star topology switch
When the switch receives a signal, it uses a table to identify which device is where, and so only sends it to the correct device. This has higher security and speed.
Star Topology Reliability
Failure of any individual device or cable will only cause the effected device to fail, but failure of the hub or switch, will cause failure in every device.
PAN, LAN, WAN
PAN stands for personal area network, for connected devices within a few metres of each other. LAN stands for local area network, connects devices is a small geographical area, like a house or a school.
WAN stands for wide area network, connects two or more NETWORKS over a large geographical area.
Client-server networks
Client devices, like laptops or phones, all connect to servers if they are permitted access. Servers usually run 24/7, and hold all information for clients, allowing clients to make requests from the server, and access their data from any device on the network.
Peer to peer network
Client devices are connected directly to each other. With permission, client’s can access and share data on other devices they’re connected to. Also, devices like printers can be accessed through connection to a computer that is connected to that device.
Client server vs peer to peer
Client server is much more expensive to set up, as you need dedicated expensive servers. In terms of physical security, client server is more secure, as its easier to guard a large and secure room containing the servers, than it is to monitor each device on a peer to peer network. Servers will automatically hold and backup important data, along with likely having a designated server manager to do this. In peer to peer, users are responsible for backing up there own files. It’s not a big deal if one device on peer to peer goes down. But in client server, if the server goes down, thats a huge problem
Wireless networks security
Networks that don’t need to be wired together to share data, as they broadcast them to each other. This has much worse security, as these signals can be intercepted. These signals can be encrypted, so it’s harder to steal data.
WLAN
The most common type of wireless network, wifi. All devices based around a WAP, wireless access point, (a router). Radio signals are sent from devices to the WAP, which sends them to the desired location. To connect to a WLAN, you need to scan for SSID’s(network name) and enter a password. Open networks don’t require a password, and won’t encrypt data.
CSMA/CA
Used to avoid collisions from signals sent at the sent time. First step is to check the channel, to see if there is any signals already. To avoid collisions, if there is a signal, then it will wait a random amount of time, before repeating to the first step. If the channel is found to be free, it will send a signal, and will wait to receive conformation from the target node, if it doesn’t receive this, it will resend the signal.
Hidden node problem
When checking to see if the channel is free, it can only see so far, there could be a node out of its range sending data to the WAP, causing both nodes to send data to the WAP at the same time, causing a collision.
RTS/CTS
As a solution to the hidden node problem, a device will send a request to send(RTS) when it deems the channel to be clear. The receiving node, will then send back a clear to send(CTS), and not respond to any other RTS’s until the original one has sent all its data.
