Topic 6, Lesson 3: The Internet Computer Communications and Networking

Learning Check What is a Wide Area Network (WAN)? How is it different from a LAN? Learning Objectives: i) Describe the nature of the internet as a worldwide collection of networks. ii) Describe the hardware needed to connect to the internet, including modems and routers. iii) Explain the need for IP addressing of resources on the internet and how this can be facilitated by the role of DNS services. Networking – The Internet

LANs and WANs LAN – Local Area Network – Located on one site – Owner of network owns the infrastructure WAN – Wide Area Network – A series of LANs connected together – Covers multiple sites – Often covers a large geographical area – Relies on infrastructure provided by other companies, e.g. telecoms companies

Today we will discuss how The Internet works, & related topics …

The Internet is … A worldwide network of networks. Linked by a common set of protocols (TCP/IP). Used by billions. Supports many applications such as – the world wide web; – instant messaging; – file transfer; – . Learning Objectives: i) Describe the nature of the internet as a worldwide collection of networks. ii) Describe the hardware needed to connect to the internet, including modems and routers. iii) Explain the need for IP addressing of resources on the internet and how this can be facilitated by the role of DNS services. Reliable because of redundancy. - Many alternative routes available from A to B.

Modems – Computers use digital signals. – Globally, many internet connections are still made via the Plain Old Telephone System (POTS). – Many telephone systems use analogue signals. – This requires a modem (modulator / demodulator) to do the conversion. – This is not needed if a digital link is used. Learning Objectives: i) Describe the nature of the internet as a worldwide collection of networks. ii) Describe the hardware needed to connect to the internet, including modems and routers. iii) Explain the need for IP addressing of resources on the internet and how this can be facilitated by the role of DNS services.

Bandwidth and Broadband Bandwidth is the difference between the upper and lower frequencies in a set of carrier signals. – it is often taken to mean the rate of data transmission in a network. Broadband means a channel carries many frequencies. – This means that it has bigger data carrying capacity than narrow band. – > 4 Mbit / sec is considered to be broadband Learning Objectives: i) Describe the nature of the internet as a worldwide collection of networks. ii) Describe the hardware needed to connect to the internet, including modems and routers. iii) Explain the need for IP addressing of resources on the internet and how this can be facilitated by the role of DNS services.

ADSL and Cable ADSL Asymmetric Digital Subscriber Line ; uses spare capacity on POTS (Plain Old Telephone Service); more bandwidth in the down direction than in the up direction; most users download more than they send. Cable Subscribers to cable TV can access the internet via a cable modem. Learning Objectives: i) Describe the nature of the internet as a worldwide collection of networks. ii) Describe the hardware needed to connect to the internet, including modems and routers. iii) Explain the need for IP addressing of resources on the internet and how this can be facilitated by the role of DNS services.

Routers A router is a device that connects networks. It selectively passes data between networks. They are at the heart of the internet. They guide data packets to their destination. ADSL modems often have router functionality built in for home networking. Learning Objectives: i) Describe the nature of the internet as a worldwide collection of networks. ii) Describe the hardware needed to connect to the internet, including modems and routers. iii) Explain the need for IP addressing of resources on the internet and how this can be facilitated by the role of DNS services.

IP addressing Every node on the internet has an IP (internet protocol) address. Just like any network, an IPv4 address is made from four 8-bit numbers, e.g Private networks have their own IP addresses. The router that connects a network to the internet has an IP address. Because every node has its own IP address, data can be sent and received on the Internet. Without them, computers wouldn’t know where data needs to be sent to. Learning Objectives: i) Describe the nature of the internet as a worldwide collection of networks. ii) Describe the hardware needed to connect to the internet, including modems and routers. iii) Explain the need for IP addressing of resources on the internet and how this can be facilitated by the role of DNS services.

DNS Serves DNS servers change domain names, such as bbc.co.uk, to IP addresses. So when you type in a web address into your browser, the address is sent to a DNS server, which looks up the address and finds the IP address of the node which hosts that website. Your computer then uses the IP address to access the website. Learning Objectives: i) Describe the nature of the internet as a worldwide collection of networks. ii) Describe the hardware needed to connect to the internet, including modems and routers. iii) Explain the need for IP addressing of resources on the internet and how this can be facilitated by the role of DNS services.

How The Internet works …

Activity Create an illustration to describe how the internet works. Use your own research to help. Success Criteria: You must make reference to : Hardware (modems & routers) IP addressing & DNS services Learning Objectives: i) Describe the nature of the internet as a worldwide collection of networks. ii) Describe the hardware needed to connect to the internet, including modems and routers. iii) Explain the need for IP addressing of resources on the internet and how this can be facilitated by the role of DNS services.

Learning Check What is the Internet? What hardware is needed to connect? What is the purpose of IP addressing? Learning Objectives: i) Describe the nature of the internet as a worldwide collection of networks. ii) Describe the hardware needed to connect to the internet, including modems and routers. iii) Explain the need for IP addressing of resources on the internet and how this can be facilitated by the role of DNS services.