1. Unit 6.10 – L1 Structure of the Internet
Objectives:
Understand the structure of the Internet
Describe the term ‘Uniform Resource Locator’ in the context of networking
Explain the terms ‘domain name’ and ‘IP address’
Describe how domain names are organised
Understand the purpose and function of the Domain Name Server (DNS) system
Explain the service provided by Internet registries and why they are needed
To explain the structure of the Internet, explain key terms of networking and describe the purposes of Internet services.

2. A short history…
The Internet is… A network of networks set up to allow computers to communicate with each other globally The World Wide Web is… A collection of web pages that reside on computers connected to the Internet The WWW uses the Internet as a service to communicate the information contained within these pages
Question Give one example of where the Internet can be used without the World Wide Web.
Answers include: file transfer via ftp, using a non-web-based client, remote access and control of a computer / telnet services, usenet groups, smartphone apps, peer-to-peer file sharing networks and instant messaging
To explain the structure of the Internet, explain key terms of networking and describe the purposes of Internet services.

3. Physical Structure of the Internet
Each continent uses backbone cables connected by trans- continental leased lines fed across the sea beds. National Internet Service Providers (ISPs) connect directly to this backbone and distribute the Internet connection to smaller providers who, in turn, provide access to individual homes and businesses.
To explain the structure of the Internet, explain key terms of networking and describe the purposes of Internet services.

4. Internet Registries and Registrars
Internet Registrars
Internet Registries
Ensures a domain is only used by one organisation
Hold records and details of all existing websites
Details of domains available for purchase
They are companies that act as resellers for domain names and allow people and companies to purchase them.
All registrars must be accredited by their governing registry.
Five global organisations governed by the Internet Corporation for Assigned Names and Numbers (ICANN)
Worldwide databases that hold records of all the domain names currently issued and their details including:
Registrant’s name
Type (company or individual)
Registered mailing address
Registrar that sold the domain name
Date of registry
They allocate IP addresses and keep track of which address(es) a domain name is associated with as part of the Domain Name System (DNS).
To explain the structure of the Internet, explain key terms of networking and describe the purposes of Internet services.

5. Uniform Resource Locators (URLs)
A URL is…
The full address for an Internet resource
URLs:
Specify the location of a resource on the Internet, so a browser can request it from a server
Includes the name and (usually) file type
Example
Method
Host
Location
Resource
To explain the structure of the Internet, explain key terms of networking and describe the purposes of Internet services.

6. Domain Names and the Domain Name System (DNS)
A domain name identifies the area or domain that an Internet resource resides in.
These are structured into a hierarchy of smaller domains and written as a string separated by full stops as dictated by the rules of the Domain Name System (DNS).
To explain the structure of the Internet, explain key terms of networking and describe the purposes of Internet services.

7. Domain Names and the Domain Name System (DNS)
Each domain name has one or more equivalent IP addresses. The DNS stores domain names/IP addresses in global directories that domain name servers can access to find the an IP address location for a resource. When a webpage is requested via URL, the browser requests the corresponding IP address from a local DNS.
If that DNS does not have the correct IP address, the search is extended up the hierarchy to another larger DNS database. The IP address is located and a data request is sent by the user’s computer to that location to find the web page data.
To explain the structure of the Internet, explain key terms of networking and describe the purposes of Internet services.

8. Domain Names and the Domain Name Server (DNS)
Example
mail.websitename.co.uk
Fully Qualified Domain Name (FQDN)
Website Domain Name
Host
Website
Company 2LD
Country TLD
Domain names are much easier for humans to remember and type in than a string of numbers in an IP address.
Question
Why are IP addresses not used to access websites instead of alphanumeric addresses?
To explain the structure of the Internet, explain key terms of networking and describe the purposes of Internet services.

9. Fully Qualified Domain Names (FQDN)
IP Addresses
Includes the host server name
E.g. www, mail, ftp
Written as:
mail.websitename.co.uk
ftp.websitename.co.uk
A unique address assigned to a network device.
Performs a similar function to a home mailing address.
Indicates where a packet of data is to be sent/has been sent from.
Routers can use this address to direct the data packet.
To explain the structure of the Internet, explain key terms of networking and describe the purposes of Internet services.

10. Tasks Classwork Complete: PPT Tasks Exercise Questions Homework
Complete 6.10 L1 Homework
Due Friday 26th April
To explain the structure of the Internet, explain key terms of networking and describe the purposes of Internet services.

11. Plenary
An example of a Uniform Resource Locator (URL) is (a) What part of the above URL constitutes the domain name? ___________________________________________________________________ (1) (b) Using the URL, explain what each part can tell us. (i) http___________________________________________________________ (ii) www__________________________________________________________ (iii) bbc___________________________________________________________ (iv) co____________________________________________________________ (v) uk____________________________________________________________ (vi) history_________________________________________________________ (6)
(a)     bbc.co.uk; 1
(b)     (i)      (hypertext transfer) protocol / protocol used / set of rules used;
R http format
(ii)     www means it is a web site/web page/is on the web; R Internet
on a web server/the machine name;
world wide web on its own n.e.
(iii)     (bbc is the)) organisation’s/company’s name/keyword/identifier/ site name/site owner;
(iv)    (co means it is a) company; A corporation; the type of organisation;
(v)     uk means the country of origin is the UK/based in UK/A site in the UK;
where it is based/located;
(vi)    History is the folder name/subdirectory
(which contains a file with default name of index.html);
OR A history is the page/filename of the web site/part of the site;
A (specific) topic; 6
(c)     (i)      Domain name has a single IP address;
Computer looks up domain name on a (domain) name server
Which tells the computer the IP address;
Domain name is user-friendly representation of IP number;
IP number/address is numerical representation of domain name;
Domain name maps onto IP address; one-to-one;
(ii)     / 0;
To / / ; ;
Each group of digits is in the range 0-255;; 2
To explain the structure of the Internet, explain key terms of networking and describe the purposes of Internet services.