Theory: Communication And Networking Flashcards
1
Q
Define Baud rate
A
The number of distinct symbol changes in the medium (signalling events) made per second
2
Q
Define bit rate
A
The number of bits transmitted over the medium per second to represent a continuous medium (audio) / value being recorded.
3
Q
Define bandwidth
A
(In hertz) the range of frequencies a communication medium is capable of transmitting.
Higher bandwidth results in a larger bit rate.
4
Q
Define latency
A
-The delay during data transfer
-More specifically the delay between data transfer and the instruction for data transfer
-(in milliseconds) the difference in time between an action and its effect being noticed.
-increases with distance
5
Q
Define protocol
A
- rules for communication between devices.
-A set of rules or procedures for (? formatting and) transmitting data between electronic devices.
-international organisations decide upon and publish protocols
6
Q
Define a symbol
A
A particular pattern of bits represented by a signal. A symbol of four bits might be 1101.
7
Q
Define serial data transmission
A
Data is sent one bit at a tine over one communication wire (metal wire, optical fibre, wireless channel)
8
Q
Define parallel data transmission
A
Uses numerous parallel communication lines to send multiple bits simultaneously
9
Q
Advantages of serial data transmisson
A
-Serial data transmission can be used over longer distances ( like with wired peripherals)
-does not have the issue of skew or crosstalk, so data is less vulnerable to corruption.
-cheaper to install than parallel mediums
10
Q
Define synchronous data transmission
A
-A clock signal shared by both the sender and the receiver times when signals are sent
(Used within the busses of a computers processor)
-signals are sent at regular intervals and received in the same order
-used in real time systems
-sender and receiver must use the same baud rate, only need to synchronise clocks for the length of transmission
11
Q
Define asynchronous data transmission
A
-Start and stop bits are used to indicate the duration of a transmission.
-the start bit is either a 1 or 0 and the stop bit is always the opposite.
12
Q
What is a start/stop bit?
A
Indicates the beginning and the end of a transmission in asynchronous data transmission
13
Q
Define physical network topology
A
Refers to the actual, physical architecture of a network
14
Q
Define physical star network topology
A
-each client (device on a network) has its own direct connection to a central hub.
-The hub receives packets for all clients and forwards it to the correct recipient.
-a server can be connected just like other clients.
15
Q
Define physical bus topology
A
-clients are connected to a single cable called a backbone with a TERMINATOR at either end of the backbone.
-no need for a central hub, server is connected to backbone
16
Q
Define logical network topology
A
-Refers to the FLOW OF DATA PACKETS within a network
17
Q
Define mixing topologies
A
-a network can be set up physically as a star topology, but function logically as a bus topology if a bus protocol is run.
18
Q
Define client server networking
A
-one/many central server(s) provide services to clients on a network.
-clients and servers are connected to a network in the same way, but a server is often a more powerful machine
19
Q
Define peer to peer networking
A
-services are provided by the clients, every client has equal status
20
Q
What is carrier sense multiple access with collision avoidance
A
A protocol used in wireless data transmission that attempts to avoid collisions by listening for a transmission signal from other devices before sending. Used in combination with RTS/CTS to prevent collisions with devices outside of range that are undetected.
21
Q
What does www stand for?
A
World wide web
22
Q
What is the difference between the internet and world wide web?
A
the Internet is a global connection of networks while the Web is a collection of information that can be accessed using the Internet. In other words, the Internet is the infrastructure and the Web is a service on top.
23
Q
What does url stand for?
A
Uniform resource locator
24
Q
What is a URL and how does it differ from a domain name?
A
A URL is the whole web address, where the domain name is a part of the web address. A url is a reference to a web resource that specifies its location on a computer network and how to retrieve it.
25
Define a domain name
They hide IP addresses with something more memorable as it would be inefficient to have to enter an IP address. Sort of a “nickname” for the IP address.
26
What is DNS?
Domain name system, hierarchical naming system for computers, along with other resources on the internet
27
What is an IP address?
Internet protocol address. A unique numerical identifier for every device or network that connects to the internet.
28
What is an FQDN?
•Fully qualified domain name: consists of three labels, hostname, second level domain name and top level domain name (TLD)
www. networksolutions .com.
•A domain that specifies an exact resource and can be interpreted in only one way. A FQDN will always include the server’s host name.
29
what is PQDN ?
Partially qualified domain name refers to one or two of the labels of a FQDN. The trailing full stop is typically left off
30
What is WHOIS, SEO and ICANN ?
-SEO = search engine organisation
-WHOIS protocol provides you with data about the owner of a website/domain
-ICANN = Internet Corporation for Assigned names and numbers, a gov non profit corporation responsible for internet protocol (IP) address space allocation and DNS management.
31
Identify the parts of the url in:
http://www.craigndave.org/thenumbers/2017/09/cryptic_challenge.pdf
•method: https
•host: www
•domain name: craigndave.org
•FQDN: www.craigndave.org
•location: thenumbers/2017/09
•resource: cryptic_challenge.pdf
32
Define Asynchronous transmission
The transmission of data intermittently between devices without the use of an external clock signal
33
What is parallel data transmission?
Transmission of data through multiple channels which allows several bits to be transmitted at a time
34
What is serial data transmission?
The transmission of data through a single channel , a single bit at a time
35
What are advantages of serial data transmission over parallel data transmission?
-there are fewer errors
-less noise (external and unwanted information that interferes with a transmission signal)
36
What is the start bit?
The bit used to indicate the beginning of a unit of data in asynchronous data transmission. (A flag for the beginning of a block of data)
37
What is the stop bit?
The bit used to indicate the end of a unit of data in asynchronous data transmission
38
Define synchronous data transmission
The transmission of data as a continuous between devices whose time signals are synchronised via a common clock
39
Define bandwidth
The range of frequencies at which data can be transmitted through a channel measured in Hz
40
Define Baud rate
The number of symbol changes, wafeform changes or signalling events across a channel per unit time
41
Define Bit rate
The number of bits transmitted per unit time
42
Define latency
The time delay between the transmitter sending data and the recipient receiving it. (Aqa)
43
Define a logical bus topology
A network that operates logically as a bus topology. A network arrangement where every host computer is connected to a single main data cable. All the nodes and switches are connected to only one single cable/bus.
44
Describe a physical star topology
A network arrangement where every host computer has a dedicated connection to a central hub computer or switch.
45
What is troubleshooting?
Tracing and correcting faults in an electronic system
46
What are some advantages of a bus topology?
-cheap to set up
-easy to set up
47
List some cable types and where they are used
-coaxial
used to transmit high frequencies with low noise interference- insulated. Bus topology
-fibre optic
-ethernet
48
What is a client server network?
A type of network organisation where networked computers (clients) connect to one or more powerful central computers (servers) that handle service requests and has resources
49
Describe a peer to peer network
A type of network organisation where networked computers are connected to each other with equal status (are both clients and servers) and share resources and workloads without a central server
50
Describe CSMA/CA
CARRIER SENSE MULTIPLE ACCESS w/ COLLISION AVOIDANCE
a wireless protocol where computers attempt to avoid interference or collision in a channel by only transmitting data when a channel is sensed to be idle.
51
Describe collisions in a channel in wireless networking
Multiple devices attempting to transmit data through the same channel at the same time ??
52
Define MAC address
MEDIA ACCESS CONTROL ADDRESS
a hardware identification number assigned to network interface cards used to uniquely identify a device on a network for communication purposes
53
How long is a mac address?
48 bits or 6 bytes can be in 12 hexadecimal digits eg. 00:1b:63:84:45:e6
54
Describe RTS/CTS
REQUEST TO SEND/ CLEAR TO SEND
a protocol to prevent data collision during transmission on a wireless network, involving the transmitter sending an RTS to the receiver, and the receiver sending a CTS back to confirm it is idle.
55
What is the difference between viruses, worms and trojans?
Viruses must be triggered by the host/victim’s interaction with the infected file. worms are stand-alone malicious programs that can self-replicate and propagate independently. Trojans mislead the user of their intent and are not self replicating.
56
How can a computer be protected from malware?
-updated software
-antvirus software
-strong password security
-educated user
-firewalls
57
List preventative measures against phishing attacks
-anti-spam software
-checking validity of emails
-not clicking on links in emails from unknown senders
-not giving out important information
58
How can you avoid intrusion on a wireless network?
-restricting access to the network
-encrypting data on a network
-firewalls
-private SSID
59
How could brute force attacks be avoided?
-using strong passwords
-limiting login attaempts
-monitoring IP addresses
–using 2FA
60
What is a firewall?
•Hardware/software placed between the user‘s computer and an external network (eg internet) to filter data
•can be installed on servers, computers or routers
•A computer that consists of two network interface cards, one connected to the internal network and one connected to the external network.
•Checks whether the incoming and outgoing data meets the requirements imposed by the network manager
61
What is a firewall? (Short)
Hardware or software placed between the user‘s computer and an external network to filter data in and out of the computer
62
Define static filtering
In a firewall, the source and destination IP addresses of a packet are inspected. If either are not allowed, the packet will be dropped or a warning may be issued.
Packets may also be filtered by the protocols used or the port trying to be accessed.
63
In networking, what is a port?
A port is a virtual point where network connections start and end. Ports are software-based and managed by a computer's operating system. A port in networking is a software-defined number associated to a network protocol that receives or transmits communication for a specific service.
64
Describe stateful inspection or dynamic filtering
This is when data packets are filtered by the payload (actual data) (payload is only part both sender and receiver see as rest of packet is stripped). If it does not form part of recognised communication, the packet is rejected.
65
Advantages of firewalls?
•Prevent malware and hackers accessing internal network
•prevent DoS attacks
•can restrict viewing of inappropriate content
66
Limitations of firewalls
•The use of modems by an internal computer to bypass a firewall cannot be stopped.
•Does not cover password strength or common sense of user
•firewalls can be disabled by a user making the computer vulnerable
•in an organisation, a network manager should control the firewall
67
What is the difference between a router and a modem?
A router creates a LAN where a modem connects directly to a ISP
68
What is a proxy server
In computer networking, a proxy server is a server application that acts as an intermediary between a client requesting a resource and the server providing that resource. It improves privacy, security, and performance in the process
69
Define a Service Set Identifier (SSID)
A local 32 character identifier for a group of wireless network devices, used to identify the network as a whole
(Network name)
70
What is Wi-Fi?
a WIRELESS LAN that is based on international standards
71
What is Wi-Fi Protected Access? (WPA/WPA2)
A security certification program that secures wireless networks by encrypting transmitted data.
72
What is a wireless network adapter?
-A physical device that allows a device or computer system to connect to a wireless network
-A physical device that creates a wireless LAN (WLAN) that allows multiple devices to connect to a wired network
73
What is a Domain name?
The name that locates a domain on the internet. It is included as part of a URL
74
Define a domain name server system
A hierarchical and decentralised naming system for computer systems connected to the Internet. It contains the IP address of all domain names on the internet.
75
What is a FQDN
-A Fully qualified domain name
-a domain name specifying the exact location of a domain in the Domain Name Server System hierarchy
76
What is a gateway?
A device that allows data to flow from one network to another.
77
What is the internet
A global network of computers systems communicating using TCIP/IP
78
What are Internet registries?
-organisations that manage the allocation and registration of internet number resources within a region of the world
-internet number resources include IP addresses and autonomous system numbers.
79
FTP:
-FILE TRANSFER PROTOCOL
-port 20/21
-used for sending files between devices
-FTP servers can be accessed anonymously or using a username or password
80
SSH:
-SECURE SHELL
-port 22
-used for remote management of computers
-requires a username and password combination and encrypts information in transmission
-
81
HTTP:
-HYPERTEXT TRANSFER PROTOCOL
-port 80
-used to deliver web pages that are stored in text form in web servers to a client
-application software on client computer receives text file and renders them as web pages
82
HTTPS:
-HYPERTEXT TRANSFER PROTOCOL SECURE
-port 443
-same function as HTTP, only encrypts information during transmission
-encryption keeps information secure and untampered/unmodified
83
POP3:
-POST OFFICE PROTOCOL 3
-port 110/995
-used for retrieving emails from an email server
-communicates with email servers, checks and downloads new messages
84
SMTP:
-SIMPLE MAIL TRANSFER PROTOCOL
-port 25/587/465
-used for sending emails.
-used between client and email server
85
Uses for SSH:
Secure shell:
-connect to servers
-make changes
-perform uploads
-exit
-provides secure encrypted connection between two hosts over an insecure network
86
UDP
-USER DATAGRAM PROTOCOL
- a transport layer communication protocol
-used for time sensitive transmissions like video playback or DNS lookups
-fast because it doesn’t formally establish a connecton before transporting data. Means data packets can be lost.
87
VOIP
-VOICE OVER INTERNET PROTOCOL
-typically used over UDP, for internet based telephone services
88
Advantages of parallel data transmission
-faster as more bits are transfered at once
89
Disadvantages of serial data transmission
Slower than parallel data transmission
90
Disadvantages of parallel data transmission
-can not be used over longer distances
-skew
-crosstalk
91
Define skew
Differing (electrical) properties of each wire in parallel can cause bits to travel at different speeds, arriving at different times.
92
Define crosstalk
When communication lines are tightly packed, signals can leak from one line to another. Data is corrupted.
93
Why can’t parallel data transmission be used over longer distances?
-skew gets worse
-also much more expensive to install
So parallel is used over short distances, like between components of the processor and within RAM
94
Define handshaking
Before communication between two devices, a protocol to use is decided upon.
95
List some protocols
-FTP
-HTTP/S
-SMTP
-POP3
-SSH
96
What are advantages of a physical star topology?
-packets sent directly to recipient, other clients cannot see.
-easy to add and remove clients/servers from the network
-just one device per cable, no collisions
-failure of one cable doesn’t affect whole network.
97
Disadvantages of a physical star topology
-If central hub goes down, whole network communication is stopped
-expensive to install, lots of caple.
98
Advantages of physical bus topology?
-no central hub, reducing chance of whole network failure
-cheaper to install, littke cable needed.
99
Disadvantages of a physical bus topology?
-packets sent through a shared cable, each client can see others intended packets.
-risk of collisions on backbone
-if backbone fails, whole network unusable.
100
Describe a logical bus topology
-packets are delivered to ALL CLIENTS on the network
101
Define a logical star topology
Packets are only delivered to the intended recipient.
102
Why are client server networks used?
-in schools and businesses, central management of clients on a network
-improves security but can be difficult to set up
103
Advantages and disadvantages of peer to peer networks
-more cost effective
-no need for a powerful server
-easier to set up and maintain
-all clients in a network must be running for the network to be fully operational
104
Describe wireless networking
-Allows clients to communicate within a network without being physically connected to it
105
List equipment required for a wireless network to run
-Wireless access point (connects to a wired network)
- wireless network adapter (in a device, connects to wap)
106
What is the difference between TCP and UDP?
-UDP is faster but less reliable than TCP
-TCP involves handshaking where UDP doesn’t
-if a packet is lost TCP requests resending, where UDP does not.
107
Describe the structure of the internet
-a network of interconnected computer networks
-using end-to-end communication protocol
-mostly a wired network with cables that pass under oceans to connect to other continents
108
Describe an ISP
-provides its customers with access to the internet
-largest ISPs are national companies referred to as NISPs, national internet service providers
109
Describe a packet and a packet switched network
-a ”container” in which data is transmitted over networks
- a packet switched network is one in which data is sent in packets
-one message is frequently split into multiple packets and sent to the recipient via the best possible route
-reassembled at destination
110
What happens when packets are sent through a network?
-the packet passes through a number of routers before reaching its destination.
-a router uses the recipient address on the packet to determine where to send the packet
-the passing through a router of a packet is called a “hop”
111
Describe the concept of hops
-a hop is each time a packet passes through a router
-each packet has a time to live (TTL) which defines how many hops the packet can partake in
The TTL is reduced with each hop.
-when a TTL expires, the packet is DROPPED or deleted
-the recipient must request the packet to be sent again
112
What are the components of a packet?
-senders address
-recievers address
- Packet contents
-TTL
-sequence number
113
Describe the properties of a router
-send packets to recipients via fastest possible route
-decided via lowest number of hops or least congested route
-hold tables with information of fastest routes to certain devices
114
What happens when two networks use different protocols?
-packets are modified to conform to different protocols.
-gateways strip away the packets details, leaving just the packet content. Then add on new sender and receiver addresses to comply to a different protocol
115
What is a URL?
-UNIFORM RESOURCE LOCATOR
-an address assigned to files on the internet
-different protocols can be used to access different files in different ways.
116
Parts of URL?
-https://
protocol used to access a file
-www
Subdomain for world wide web. Points to web server hosted at following domain
-bb.co.uk
Domain. .uk is a TLD, .co is a 2LD
-
117
What is REST?
-a design methodology for online database applications that are queried by a web browser
118
What HTTP requests does REST use?
POST(INSERT), GET(SELECT), PUT, DELETE
119
Describe the components of a packet and their purpose
-senders address: identifies where the packet was sent from and where a response should be sent
-receiver's address: identifies intended recipient so packet is routed to right device
-packet contents: the data that is being transferred
-TTL: time to live, describes how many hops the packet has left before it is dropped
-packet sequence number: describes the position of the packet in relation to the other packets being sent.
120
What is the purpose of a Domain name?
As IP addresses can't just be remembered, Domain names map to an IP address: human-friendly IP identifier
121
What is the purpose of a DNS?
as a domain name is entered into a browser, a DNS (domain name server) is used to translate the domain name into it's IP address
122
Why may rarely visited websites take longer to load?
Because the Domain name/IP address will not be found on as many DNSs. This means the request is passed around DNS servers until a record of the Domain name is found.
123
What is an internet registry?
-organisation responsible for the allocation of IP addresses
-only 5 in operation, for 5 different geographical areas
124
What are the roles of internet registries?
-allocate IP adresses
-protect the world's depleting pool of unallocated IP addresses
-before allocating a new IP address, internet registries look for previously used IP addresses that are unused
125
What is the function of a firewall?
-sits between a device/network and the internet and regulates packets that pass through it
-can be hardware or software
-can work as a proxy server, which does packet filtering and stateful inspection
126
Describe the process of packet filtering
-packets are accepted or blocked based on their source IP address or protocol being used
-admin can block specific IP addresses or protocols or use automatic filtering software
127
Describe stateful inspection
-Examines the content of a packet before letting it through a firewall
-some firewalls keep a record of current connections/conversations and rejects packets that aren't related to recent activity
128
What is a proxy server?
-A server that sits between a public and a private network
-manages every packet that passes through
129
What makes proxy servers so secure?
-the senders IP address in a packet is that of the firewall, not of the sender
-user's IP address is masked when sending packets across a public network.
130
Describe symmetric encryption
-both sender and receiver share the same private key
-same key is used to encrypt and decrypt data
131
What is the flaw of symmetric encryption
-a key needs to be exchanged between the sender and receiver
-if a key is not exchanged in person, it is vulnerable to interception
132
Describe asymmetric encryption
-four different keys used
-each device has a pair of mathematically related keys (public and private key)
-a message encrypted with a senders
133
What are TCP and UDP examples of?
Transport protocols
134
What does TCP stand for?
Transmission control protocol
135
What does DHCP stand for? What does it do?
Dynamic host configuration protocol. Assigns private IP addresses from a pool of available private IP addresses within a private network.
136
What does NAT stand for? What does it do?
Network address translation. Used to translate private IP addresses into public IP addresses etc
