1
Q
structure of the internet
A
- main part of the internet is known as the backbone
- these connect several large networks around the globe
- each are then controlled by ISP’s for the end user
2
Q
what is an ip address
A
*set of rules for communcation on the internet
*ip address indentifies a network or device on the internet
3
Q
what parts does the IP address consist of?
A
network ID comprising of the first three numbers of the address and a host id, the fourth number in the address.
4
Q
what is IPv4
A
made up of four octet values sperated by a fullstop. this doesnt allow us to represent enough addresses
5
Q
what is IPv6
A
uses 128 bits to represent as eight group of four hex numbers
6
Q
differences between IPv4 and IPv6
A
- ipv4 is 32 bit but ipv6 is 128 bit
- ipv4 is numeric addressing but ipv6 is alphanumeric
- ipv4 bits are seperated by a dot ipv6 are seperated by a colon
7
Q
what is a url
A
uniform resource locator is used to specify the means of accessing a resource and its location across a network. protocol and domain name of the resource together.
8
Q
what is a dns
A
- servers with an index of domain names with their corresponding ip.
- need to be unique so organization cant have the same names
- registered with a central agency called icann
9
Q
what do dns servers do when they are unable to find a website
A
- several severs catalogue every web domain name
- they are segmented into geographical groupings
- when it cannot locate the ip it sends queries to relating servers
10
Q
what is a fqdn
A
- fully qualified domain names
- can be broken into constituent parts including host name and domain name itself
11
Q
resolving an IP address
A
12
Q
what is circuit switching
A
creating a communication connection between two endpoints for the duration of a phone call or transfer of data
13
Q
what is packet switching
A
packets are often sent across networks that have multiple links with multiple routes through to a destination
14
Q
how does routing data packets work?
A
- each router stores data about the available routes to the desintation node
- looks up the destination IP in its routing table to find the best router to forward the packet
- each forwarding is known as a hop
15
Q
what does a packet consist of?
A
16
Q
why are packet sizes small?
A
- they are kept small to ensure that individual packets do not take excessive time to transfer.
- they shouldnt be too small as the additional data added makes data transfers inefficient as unnecessary headers would be added each time
17
Q
what does the paket header contain
A
- recipient address so it can be directe properly
- address of the sender is included so replies can be sent properly
- packet number and overall number of packets is attached to aid in reassembling data
- time to live or hop limit is also included
18
Q
what does the packet trailer contain
A
- error checking components that verify the data received in the payload isnt corrupted
- checksums or cyclical redundancy checks are used to check the data by the receiving host
- if checksums dont match the data has become corrupted
19
Q
what is a gateway
A
- required where data is travelling from one network to another that use different protocols
- networks using different transmission media require this
- header data are removed and reapplied using the correct format
- router and gateway can be combined to one device
20
Q
what is a firewall
A
- software or hardware that controls access to and from a network
- numbered ports are opened so that only certain traffic is allowed to pass through
21
Q
how does packet filtering work?
A
- packets are inspected by the firewall
- different network protocols use different ports
- if this traffic is allowed the port must be open for the duration otherwise it will automatically reject it
22
Q
what is stateful inspection
A
examines the payload of a packet before allowing access and remembers actions fof future decisions.
23
Q
what is a proxy server
A
- makes web requests on behalf of your own computer hiding the true request ip address from the recipient
24
Q
functions of a proxy server
A
- enables anonymous surfing
- can be used to filter undesirable content online
- logs user data with their requessts
- provides a cache of previously visited sites to speed access
25
what is encryption
* the act of encoding plaintext so that it cannot be undeciphered unless you have a key.
26
what is symmetric encryption
* uses the same key to encrypt and then decrypt the data being transferred.
* key has to be transferred between the communicating devices so that they both understand how to pass messages
27
what is a mitm attack
once they have the key all that is required for an attacker is to sit in the middle of a conversation and behave as the other party
28
benefits of symmetric encrpytion
* fast form of encryption
* communicating devices have to transfer the key between them so that hey both understand how to pass messages
29
asymmetric encryption
* uses two seperate but related keys
* public key used to encrypt data before sending
* private key decrypts the data
30
digital signatures
* to verify the integrity of a message, the sender can add a digital signature to a message
* irreversibly reducing the unencrypted message to produce a hash
* encrypting their hash using their private key
* sender bundles digital signature with message and encrypts bundle using public key
31
what is a worm
* a worm is a standalone program that does not require a user to run it in order for it to spread
* worms exploit vulnerabilities in the destination system and spread automatically
32
trojans
* malicious pieces of software that masquerade as something seemingly useful.
* cannot self replicate
* open backdoors in computer to the internet
33
what is phishing
* using email to manipulate a victim into visiting a fake website and giving away personal information
34
what is buffer overflow
* occurs when a program accidentally writes data to a location too small to handle it
* overflowed data may end up in an instruction space
* malware can deliberatley cause this to execute instructions
35
what is an sql injection
* user can enter sql commands via online database forms to change the processing
36
what are the layers of the tcp/ip stack
* application layer
* transport layer
* network layer
* link layer
37
purpose of application layer
* used to provide services for applications that want to commuinicate across a network
* uses high level protocols that set an agreed standard between communcation end points
* specifies the rules of what should be sent
38
purpose of transport layer
* uses tcp to establish end to end connections witht he recipient computer
* splits data into packets and numbers them
* adds the port number to be used
* confirms packets have been recieved and requests missing packets
39
purpose of network layer
* internet protocol to address packets with the source and destination ip addresses
* forwards each packet towards an endpoint
* each router uses a routing table to instruct the next hop
40
purpose of link layer
* operates across a physical connection
* adds the mac address of the physical nic that packets should be sent to
* mac addresses can change with each hop
41
process of recieving data through ip stack
* link layer removes the mac address from each packet and passes it to the network layer
* network layer removes ip address from each packet and passes it to the transport layer
* transport layer removes the port number from each packet and reassembles packets ni the correct ortder
* application layer presents the image data for the user in a browser
42
what is a mac address
* uniquely identifies a physical device with a NIC
43
port numbers
* port is used to alert a specific application to deal with data sent to a computer
44
transferring files with ftb
* application level protocol used to move files across a network
45
what is ssh
secure shell is an encrypted protocl that allows secure communcation between nodes across a network. ssh uses public key encryption to protect data
46
sending and recieving emails
* smtp: used to send emails and forward them between mail and servers to their destination
* pop3: downloads email stored on a remote server to a local client
* imap: manages emails on a server so multipole clients can access the same email account
47
difference between pop and imap
imap holds mail on the server so that multiple devices can access all mail
pop downloads mail to a local device and removes it from the server
48
use of ip addresses
unique numerical address this identifies a host computer or network node trunk to communicate over ip on a network
49
ipv4
uses four octets(8 bits)
0.0.0.0 - 255.255.255.255
50
broadcast address
the last address in a network x.y.z.255 is reserved as the broadcast address on that network for sending data to all hosts on that network
51
ipv4 vs ipv6
ipv4 only provides a maximum of 2^32 addresses
ipv6 uses 128 bits as a string of 32 hexadecimal
52
parts of an IPv4 address
*network identifier - left hand bits of 32 bits number used to define the network where nodes are communicating
* host id - right hand bits of 32 bit number used to identify separate nodes
53
what is classful ip addressing
ip addresses used to be categorised into classes to identify the network and host ids of various ranges
54
what classless ip addressing is
use of a suffice such as /24 enables ip addresses to be used with varying portions of network id and host id
subnet msk is used to define network id and this can be segmented however a network admin sees fit
55
what is a subnet mask
used together with an IP address to identify the network identifier within the address
all network id bits set to 1 and all host id set to 0 so using an and operation the network is identified
56
what is subnetting
an organisation can choose to further subdivide the number of available host ids that they have between individual subnetworks
57
network address translation process
a number of devices with a private ip can use a single public ip. records the source and destination socket addresses for each request. when a response returns it is passed back to the host who made the request
58
what is port forwarding
servers accessible to the public can be given non routable IP address within a private network
a public request reaches the external router of the private network using a given port
data packets are forwarded internally to the correct device
59
what is DHCP
dynamic host configuration protocol is used to automatically assign ip addresses and any other network config information.
allows limited pools of dynamic ip addresses
allows hosts to reconfigure themselves when moving between networks
60
how does DHCP work
can assign a limited number of temporary ip addresses to transient devices operating within a local hotspot
61
application programming interface
* set of functions and protocols that clients can use
* a serverside web api is a set of web services to enable programmers to build web applications
62
limitations of http communication
* client has to request data from the server
*if too much time passes between establishing a socket connection drops to conserve resources and returns an error
63
what is the web socket protocol
includes api for establishing a persistence tcp socket connection
- connection is sumultaneous two way
- allows data to be sent at any time
- encrypted
64
what benefit does web socket protocol give in regards to smaller packets
* they contain usual headers this creates super fast connection used in websites with real-time updates
* server load is reduced saving bandwidth
65
what are the four basic data manipulation operations (CRUD)
Create - write a record to a database
Retrieve - retrieve a record from a database
Update - amend a record
Delete - remove a record from the database
66
HTTP common set of actions
Get - request data from a source
Post - submit data to be processed
Put - uploads a new resource to the server
Delete - removes a resource from the server
67
what Is Representational State Transfer
REST is architectural style which determines how systems communicate with each other
68
What is JSON
javascript object notation is written in a standard programming form like javascript
69
what is XML
Extensible markup language has a format similar to html
70
JSON vs XML
71
what are thick clients?
using standard computers as hosts and join them via a network medium
each host on the network would be a powerful computer
expensive
72
what are thin clients
use low powered processors in hosts specifically designed as network machines
processing is done on a powerful central server
simple os requiring little administration
update itself OS
powerful server and highly responsive network is required
73
thick client vs thin client
