Networks Flashcards
How are files separated so they can be sent across the Internet?
Files are separated into smaller units called packets. Each packet contains a portion of
the data, along with information that helps reassemble the packets into the original file
once they reach their destination.
What is the name of the device which directs packets across the Internet?
Router
Does your router have a connection to the router of the computer you are
communicating with?
No – packets travel through a series of routers forwarding the packet to the next router
closer to the destination
What is the physical address of your computer called?
MAC Address
What is the address used to get the packets to the correct router called?
IP Address
Software as a Service (SaaS)
subscription software delivered through the internet, usually via a web browser.
why use a Thin client
- Simpler installation/updating of software (as only done on server).
- Cheaper to purchase due to a lower hardware specification.
Why use a Thick client
Applications performance will not differ depending on network strength
Thin Client
computer where applications/programs are executed on an application server. (processes done by server)
Thick client
a computer that performs the majority of processing tasks
locally.
client server
one computer is nominated as a central server, the rest are seen as clients. (centralized management)
peer to peer network
all computers have equal status.
servers and clients
server: A server provides services required by a client
clients: requesting device
benefits vs negatives: client server
- single point of access and failure(data stored centrally)
+easier to back up and perform updates
negatives: peer to peer network
- offers less security (multiple points of weakness)
- potential data loss (self management)
benefits:
peer to peer network
+ each node can request and provide to each other
+ potentially more cheaper to set up
Packet Switching
Routers switching packet destinations via the routing table to make an efficient hop
benefits: serial
+ cheaper and still fast
+ doesn’t suffer crosstalk
Benefits: parallel
+ faster since simultaneous
+ reduced latency
synchronous
transfer at regular intervals, receiver and transmitter (continuously) synchronized by system clock pulses.
Asynchronous
Start and stop bits to synchronize receiver and transmitter devices temporarily
Latency
Time delay between data being transmitted and data arriving
Baud rate
Rate at which signal changes (pulses/second)
Bit rate
Rate of data transmission (bits per second)
Bandwidth
range of signal frequencies that can be transmitted (simultaneously) through a transmission medium (Hz)
POP3 (Post office protocol v3)
RETRIEVES MESSAGES FROM MAIL SERVERS
IMAP (internet access protocol)
RETREIVES MESSAGES FROM MAIL SERVERS
SMTP
TRANSFERS DATA TO MAIL SERVERS
SSH
SSH: Used for the management, access and control, remotely.
requires username/password combo and encrypts information during transmission.
DNS servers
translates each (URL) request into an IP address (DNL resolution)
(now built into devices)
Network devices and their operations (3)
Hub sends to all
Switch directs to specific devices
Router can send between networks
repeaters
Repeaters boost signal: needed over long distance 🗣️
SSID
Display identifier for people to differentiate between networks
Wireless Network Adapter
Adds wireless connectivity to (laptop) device
Wireless access point
allows Wi-Fi devices to connect to wired network point
symmetric encryption
1 key for encryption and decryption
asymmetric encryption
2 keys (private and public). only the receiver can decrypt the data encrypted with his key
Hashing
irreversible mathematical process that
produces a value from the input.
purpose of digital signatures?
confirms authentication of sender
confirms preservation of the message
Go through:
Data collision avoidance
- Sender listens for signals and will wait until clear. If data is being sent by other nodes, it will not send. (Backs
off) - When there is no signal present, the computer sends a RTS (Request To Send)
- If it goes to send data at the same time as another node, then it cancels and waits for a random amount of
time before checking again to see if the recipient is free. - The receiver (WAP in wireless networks) will send a CTS (Clear To Send) if it is ok to send.
- The RTS/CTS signals block other transmissions.
- Start to transmit when CTS received – otherwise wait until transmission has ended
- Receiver sends ack (acknowledgement) after all the data has been received
- The ack signal notifies other nodes they can transmit again
Port forwarding
external computers to connect to network nodes directly (greenlit by the router)
issues with port forwarding
internal node is immediately accessible; no longer shielded from unauthorized access
subnet mask
used to ‘mask out’ the host bits of an IP address and reveal the network to which the device belongs.
how do carry out masking
with a bitwise logical AND operation on the IP address and the subnet mask
Identifiers of a mask
- signed 32 bit number
- 1s is the network part (determines number of subnets)
- 0s is the host part (determines number of devices on a subnet)
CheckSum Error check
apply (checksum algorithm) to block of data
returns “checksum” value
value added to block of data/ packets and is used as a comparison
check digits
checks that human has input correctly 🤖
Parity Checking
Even parity is where each byte consists of an even number of 1s
Odd parity is where each byte consists of an odd number of 1s
If as odd number of bits are manipulated an error is detected
majority voting
parity checking but you send each bit 3x (to avoid mistakes)
- Role of application layer
Applies protocols for software being used to make requests to the server
- Role of transport Layer
Establishes end to end connection and performs error detection. Packets split here.
- Role of Internet Layer
Responsible for adding IP addresses of sender and recipient
- Role of the Link Layer
Physical (WiFi/Ethernet) connection established and sender and recipient MAC addresses added.
Routing happens here.
What is a Subnet?
Divisions of network that prevent unnecessary congestion during shared Bandwidth.
What is a port?
Numerical identifier that corrects data to the right software
Gateway
connects protocols on different network’s. Protocol conversion
JSON benefits over XML
Both are used to retrieve data from the web server.
1. JSON is more compact
2. JSON is faster for a computer to parse
3.JSON is easier to read for humans
difference between TCP and UDP
TCP establishes end-to-end connection whereas UDP doesn’t
UDP is faster though
difference between physical and logical topology
logical: how the data flows around the net
physical: cabling layout btw devices on the network
set of protocols for software applications to communicate with each other
API (Application Programming Interface)
REST
is the enables CRUD to be mapped to sql
uses http protocol request types to allow CRUD, using an API
CRUD
create read update delete on a database application
Internet registries (Hierarchical organisation)
Manage ownership of domain names. Can have multiple Name alternatives to remembering a specific IP address.
FTP
Sends data to file servers
HTTP(S)
establishes communication with web servers (w/ encryption)
A socket
the Ip address with a port number attached to it, assigned when the connection is agreed at the transport layer.
Well known ports
Fixed port numbers used by servers
