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44 Cards in this Set

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internet:

a global network of networks

is the internet the same as the world wide web?

no

URL:

uniform resource locator: a method for identifying the location of resources on the website.

what is each part of the web address:


http://www.awebsite.co.uk/index.html

http: protocol being used


www. : server being used


awebsite : organisation


co : type of organisation


uk : country code


index.html : file being accessed.

Domain name:

the recognisable name of a domain on the internet.

name what each top-level domain name is:


com


gov


ac


sch


org


net

commercial organisation


part of the government


academic institution


organisation of a school


organisation other than commercial business


company providing internet services

when the www is typed, what is the domain name called?

a fully qualified domain name and is completely unambiguous.

IP address:

a unique number that identifies devices on a network

Domain name server:

DNS: a server that contains domain names and associated IP addresses

why are some IP addresses private(non-routable) addresses?

they are used on a private network, like a home, schools or business. it's used to route data around the network.

ports:

used to identify a particular process or application on a network. it is a 16 bit number

what are these protocols:


HTTP


POP3


SSH


HTTPS


SMTP

hypertext transfer protocol: 80


post office protocol: 110


secure shell protocol: 22


hypertext transfer secure protocol: 443


simple mail transfer protocol: 25

how to ports work?

1) when a client sends a request to a server using a well-known port,


2) the server needs to respond by using the client port then the other port.


3) therefore, a source port must be sent so the server knows what port to use.

Domain name server system:

a system of connected domain name servers that provides the IP address of every website on the internet.

what is the system called where the private IP addresses is matched with the public ones?

Network address translation(NAT)

what are the advantages of NAT?

1: only the public IP address needs to be registered with the DNS system


2: increased level of security is the privates are not being broadcast over the internet.

what is in a translation table?

the tracking of connections and mappings between private IP addresses and port numbers with the public address.

how does NAT work?

1) the client sends packets to request some data from a server. they have the private IP address and port number so it can be sent back.


2) the router replaces the private port and IP address, with its external IP address and generated port number. the private addresses is stored in a translation table with the public addresses


3)when data is sent back, the port number on the packet is checked in the translation table


4) if there is a match, the public address in the packet is replaced with the private address from the translation table. it then goes into the private network back to the original sender.


5) if not, the packet is discarded as it could be a potential threat.

port forwarding:

a method of routeing data through additional ports

when is port forwarding used?

when a server provides services to the public from a private network

how does port forwarding work?

the router can be programmed that if a request is made to its router and it has a certain port number, then it can be forwarded to a device with a specific IP address within a network.

socket:

an endpoint of a communication flow across a computer network.

what do sockets do?

they are used to communicate the other end of the communication so that a connection can be established. for example,192.168.0.1:80 is a socket that a server will listen to. with the request, the socket address will have the clients port.

subnet Masking:

a method of dividing a network into multiple smaller networks.

why is subnet masking used?

it is easier to manage and to make it more efficient when routeing data. this means that if data is sent from one client to another, then the subnet will say whether it's on the same network or a different network.

Gateway:

a node on a network that acts as a connection point to another network with different protocols.

why should we use the IPV6 addresses than IPV4?

as the internet is expanding rapidly, there is not enough unique addresses that can be used for each device. so 128 bits with hex numbers is used to increase the amount of IP addresses.

Dynamic Host Configuration Protocol:

(DHCP): a set of rules for allocating locally unique IP addresses to devices as they connect to a network.

what is the difference between static and dynamic IP addresses?

static: are assigned to a device and never change


dynamic: allocated every time a device connects to a network.

how does the allocation of IP addresses happen?

1) it is done automatically by an application


2) the application looks for available IP addresses from its pool of addresses and allocates it to the device.

how does the domain server system work?

1) the client with the domain name is sent to its local DNS.

2) the DNS then tries to match the domain name from the request with the IP address unique to that name.


3) if there is a match, then the IP address is sent back to the client and then used to reach the specific server.


4) if there is no match, the DNS will send a request to other DNS to see if they have the match needed. if so, then its sent back to the original DNS and then back to the client.

Internet registries:

organisations who allocate and administer domain names and IP addresses

what is the hierarchical structure of internet registries, and their names?

ICANN - the internet corporation for assigned names and numbers


IANA - internet assigned numbers authority


RIR - Regional Internet Registries


NIR - National Internet Registries


LIR - Local Internet Registries



Regional internet Registry:

one of five large organisations that allocate and administer domain names and IP addresses in different parts of the world.

how is data sent through a WAN?

the packets that are sent travel through multiple nodes to get to the receiver and vice versa.

Routing:

a process of directing packets of data between networks.

how does routeing work?

it finds the optimum route between the sender and receiver. data packets are sent to the next router in the path and is referenced in a routeing table. other possible routes are also stored in the routeing table.

Packet switching:

a method for transmitting packets of data via the quickest route on a network.

what does the header contain?

MAC address of sender and receiver


sender and receiver IP address


protocols being used


packet or sequence number

what does the body contain?

the actual data

what does the footer contain?

a checksum

Checksum:

a method of checking the integrity of data by calculating a sum based on the data being sent.

why can each packet go through a different route?

the packets contain a sequence number that is used to reassemble them.

what's the use of sending packets through different routes?

this means that the packets can go through the least congested and therefore quickest route. it is also secure as it's not the same route.