Structure of the internet

what is a backbone cable?

• a set of dedicated connections that connect several large networks at various points across the globe

• they are connected by trans-continental undersea cables

• national ISPs connect directly to this backbone and distribute the internet connection to smaller providers who distribute it to homes and businesses

what is a URL?

• uniform resource locator

• the full address of an internet resource

• specifies location of a resource on the internet so that a browser can request it from the website server

• contains protocol, domain name, host, top level domain and location of file on server

what is a internet registrar?

• they hold records of all existing website names and the details of those domains that are currently available to purchase

• they are companies that can resell domain names and allow people to purchase them

• they must be accredited by a registry

what is an internet registry?

• they are five global organisations governed by the ICANN with worldwide databases that hold the records of all the domain names issued to people + details

• records contain registrar name, registrant name, date, details

• they allocate IP addresses and keep track of which addresses a domain name is associated with as part of DNS

what is the domain name

• domain name identifies the area or domain that an internet resource resides in

• contains a top level domain (eg .com .edu .org)

• domain names must be unique so that DNS requests don’t get confused

• domain names are resolved from right to left during DNS lookup

what is the DNS?

• domain name system

• it provides a set of rules for domains to follow

• each domain has one or more equivalent IP addresses

• the DNS catalogues all domain names and IP addresses in a series of global directories that domain name servers can access in order to find the correct IP address for a resource

• when a webpage is requested using the URL, the browser requests the IP address from the DNS

• if that DNS doesn’t have the correct IP address, the search is extended up the hierarchy to a root server

• once the IP address is found, the user’s computer requests the web page data

what is a fully qualified domain name?

one that includes the host server name (like www)

what is an IP address?

• a unique address assigned to a network device

• indicates where a packet of data is to be sent to or from

• routers can use it to direct the data packets

• for domain names, the IP address is the address of the server the website resides on

what is physical vs logical topology?

• physical topology= how the devices are physically laid out and wired together

• logical topology= direction in which the data travels in , how the components communicate across the physical topology

• therefore, a network can be wired as a star topology but behave as a bus topology

what is a wireless access point?

• A WAP (wireless access point) allows devices to wirelessly connect to the Internet or another wireless network.

• It has a range of about 20 metres indoors, and more outdoors.

• The WAP transmits radio waves of a fixed frequency, and all the devices within a range can receive its transmission using their station (a combination of a wireless network adaptor and the device itself).

• The stations are constantly tuned in on the WAP's frequency so they can pick up its transmissions, 

what is a mesh network?

• Every node (device) in the network is connected to every other node 

• Only one node requires an internet connection and all others can share this connection 

• The internet connected node can transmit data across any intermediate node so they can share its internet connection 

• The network is wireless so there are no cabling costs 

• The more nodes installed, the more reliable the network is because if one connection is broken or failed, the node's other connected nodes can still provide an internet connection (so the network is self-healing) 

• New nodes can be added quickly 

• Data does not need to travel via a central switch so communication is faster