3.9 Fundamentals of Communication and Networking Flashcards
Internet address
Each device on a network needs to be uniquely identified so that the data can be sent to the correct destination
what are URLs used for
URLs are used to specify the means of accessing a resource across a network and its location
how is a URL formed
the protocol and the domain name of the resoruce
URL
Uniform Resource Locator
DNS
Domain Name System
define the Internet
a network of interconnected computer networks which uses an end-to-end communication protocol
ISP
Internet Service Provider
what is an ISP?
a company that provides its customers with access to the internet
TTL
Time To Live
what name is given to the process of a packet moving from one router to another
hop
primary components of a packet
sender’s address, receiver’s address, packet contents, TTL, sequence number
gateways
a device that is used between networks that uses different protocols
purpose of a sender’s address
identifies where the packet was sent from
purpose of a receiver’s address
identifies the packet’s intended recipient
purpose of packet contents
where the packet holds the data that is being transferred
purpose of TTL
holds the number of hops a packet can go through before being dropped
purpose of sequence number
contains the number of packets in a message and identifies a packet’s position in relation to others
what is a domain name
it identifies an organisation or individual on the internet using alphanumerical characters
FQDN
Fully Qualified Domain Name
what is a FQDN
a domain that specifies an exact resource and can be interpreted in only one way, will always include the server’s host name
three types of malware
worms, trojans, viruses
worms
pieces of malware that can self-replicate between computers, either within a network or by users downloading and running a malicious file
trojans
a type of malware that is disguised as a benign file, users can be tricked into opening this as an email attachment
viruses
requires a host file to reside in, the files are typically executable, can lie dormant until the host file is opened, can spread between computers over a private network
precautions taken to prevent malware
antivirus software, employees can be trained about opening email attachments, good code quality to prevent malware exploiting bugs in code
firewalls
sit in between a device and the internet, regulates the packets that pass through them, either software or hardware, work as a proxy server to perform packet filtering and stateful inspection
stateful inspection
examines the contents of a packet before deciding whether to allow it through a firewall, can be filtered as firewalls can keep records of current connections in a network
packet
containers in which data is transmitted over networks, labelled with addresses for their sender and recipient, contains information intended for recipient
what is a packet switched network
network in which data is sent in packets
packet switched networks process
one message is split into multiple packets, each of which is sent to recipient via the best possible route, packets are reassembled with other packets, packets pass through routers before reaching destination, each packet has a finite number of hops, with each hop TTL is reduced, when TTL expires the packet is dropped, recipient will notice a missing packet and request that the sender transmit the missing packet again
how does a router know the fastest route
holds table with information relating to the fastest routes to certain devices
when must a packet be modified
where two networks use different protocols, packets must be modified by a gateway so as to conform to both protocols
packet filtering
firewalls use this to accept and block packets based on their IP address or the protocol that they are using (determined by their port number)
baud rate definition
number of signal changes per second
bit rate definition
number of bits that are transmitted per second, bits per second
bit rate formula
bit rate = baud rate x number of bits per signal
bandwidth definition
the range of frequencies that can be transmitted across a network connection
bandwidth and bit rate relationship
direct relationship, higher bandwidth = higher bit rate
latency definition
the delay between a signal being transmitted and it arriving, increases with distance
protocol definition
a set of rules (relating to communications between devices)
serial data transmission
data is sent one bit at a time
parallel data transmission
uses numerous parallel communication lines in order to send multiple bits simultaneously, more lines = more data sent at one time
disadvantages of parallel
skew may occur as bits may not arrive at exactly the same time (worse over long distances), more expensive because of multiple lines, crosstalk can occur leading to data corruption
advantages of serial over parallel transmission
doesn’t suffer from skew or crosstalk so more reliable over long distances, cheaper
synchronous transmission
when data is transmitted, a clock signal is used to time when signals are sent, signals are sent at regular intervals and received in same order
asynchronous transmission
uses start and stop bits to indicate duration of transmission, sender and receiver use same baud rate
physical topology defintion
the physical layout/architecture of the cabling
logical topology definition
how data/packets flow around a network
physical star network topology
every device is connected to central hub, every device sends data via central hub, hub sends packets of data to intended recipient only, server can be added to network
physical star advantages
failure of one cable does not affect performance of rest of network, no collisions as each cable has just one device, packets sent directly to recipients
physical star disadvantages
if central hub fails all communication is stopped, expensive to install
