1. Internet Infrastructure 1 (Review) University of Khartoum

2. THE INTERNET The Internet consists of a worldwide interconnection of governmental, academic, public, and private networks based upon the networking technologies of the Internet Protocol (IP) Suite. It is an example of a global WAN. Asia Pacific Europe/Middle East/Central Asia/Africa North America Latin American and Caribbean

3. University of Khartoum Internet history ARPANET – Implemented in late 1960’s by ARPA (Advanced Research Projects Agency of DOD) – Networked computer systems of a dozen universities and institutions with 56KB communications lines – Grandparent of today’s Internet – Intended to allow computers to be shared – Became clear that key benefit was allowing fast communication between researchers – electronic-mail (email)

4. ARPA’s goals – Allow multiple users to send and receive info at same time – Network operated packet switching technique Digital data sent in small packages called packets Packets contained data, address info, error-control info and sequencing info Greatly reduced transmission costs of dedicated communications lines – Network designed to be operated without centralized control If portion of network fails, remaining portions still able to route packets University of Khartoum Internet history

5. Huge variety of networking hardware and software appeared – ARPA achieved inter-communication between all platforms with development of the IP Internetworking Protocol Current architecture of Internet – Combined set of protocols called TCP/IP The Internet – Limited to universities and research institutions – Military became big user – Next, government decided to access Internet for commercial purposes University of Khartoum Internet history

6. Internet traffic grew (I) – Businesses spent heavily to improve Internet Better service their clients – Fierce competition among communications carriers and hardware and software suppliers – Resulted in massive bandwidth increase and plummeting costs University of Khartoum Internet history

7. Internet traffic grew(II) – Tim Berners-Lee invents HyperText Markup Language (HTML) Also writes communication protocols to form the backbone new information system = World Wide Web Hypertext Transfer Protocol (HTTP): – a communications protocol used to send information over the web – Web use exploded with availability in 1993 of the Mosaic browser – Marc Andreessen founds Netscape Company many credit with initiating the explosive Internet of late 1990s. University of Khartoum Internet history

8. W3C Founded in 1994 by Tim Berners-Lee Homepage at www.w3.org www.w3.org Goals – Internet universally accessible – Standardization – W3C Recommendations: Technologies standardized by W3C include the Extensible HyperText Markup Language (XHTML), Cascading Style Sheets (CSS), HyperText Markup Language and the Extensible Markup Language (XML). University of Khartoum World Wide Web Consortium

9. Scenario Access http://www.uofk.eduhttp://www.uofk.edu

10. Web browser. Web server. DNS. Routers. University of Khartoum Main Elements

11. University of Khartoum Web browsers Software applications for retrieving information resources on the world wide web. URL (Unified Resource Locator) used to identify the resource on the web. Examples: IE, Firefox, Chrome,....

12. University of Khartoum Web Servers Is a software that hosts web sites/web applications. Mainly use HTTP protocol to deliver the content to web browsers. Examples: Microsoft IIS & Apache.

13. University of Khartoum DNS IP addresses are how machines are located on the internet, so how come we use URIs? http://www.google.com/ Because the Domain Name System (DNS) allows use to translate a URI into an IP address (it has other functions too). It’s a bit like a phonebook for the internet. The advantage of DNS is that it allows us to assign names to organizations independent of physical routing – even if their IP addresses change.

14. University of Khartoum DNS (2) DNS was invented in 1983. The theory is straight-forward. The domain name space consists of a tree of domain names. A URL typically consists of two or more parts separated by dots – like www.google.com DNS works from right to left; in this instance: com. is the top-level domain. google. is a subdomain of.com www. is a subdomain of google.com.

15. University of Khartoum DNS (3) When you type in a URL, the top-level domain is first queried. We do this by contacting a root DNS server (there are 13), which gives us the IP address of the DNS server that has information for.com. We then contact that DNS server, and it gives us the IP address of the DNS server that has information for google.com. We contact that DNS server and it gives us the IP address of the DNS server that contains information about www.google.com. Which returns the IP address of www.google.com.www.google.com

16. University of Khartoum DNS (4)

17. A computer network is a group of interconnected computers connected together which share resources such as data, printers over a network connection. University of Khartoum Networks

18. Networks can consist of a small group of computers localized to a building or they can extend over large geographic areas. The most common types of networks include: – Local Area Network (LAN) – Metropolitan Area Network (MAN). – Wide Area Network (WAN) University of Khartoum Networks Types

19. University of Khartoum Local Area Network (LAN) A LAN is high-speed, low-error, data networks that are confined to a small geographic area e.g. within a building. Current LANs are most likely to be based on Ethernet technology. Each individual computer can access data and devices anywhere on the LAN. Local area networks (LANs) are one of the most widely used types of networks. LANs connect workstations, servers, and peripheral devices, such as printers, together.

20. University of Khartoum Metropolitan Area Network (MAN) A metropolitan Area Network (MAN) is a network that covers a metropolitan area such as a city or suburban area. MANs are larger than LANs but smaller than WANs (discussed next slide). A MAN is usually created when two or more LANs are connected together, offering high-speed connections.

21. University of Khartoum Wide Area Network (WAN) A WAN is a computer network that spans a relatively wide physical geographic area. A WAN consists of a system of interconnected LANs. WANs differ from LANs in a number of ways: – They cover greater distances than LANs. – WAN speeds are slower. – LANs primarily use private network transports while WANs can use public or private network transports.

22. University of Khartoum IP Addresses The internet is all about computers and resources connected together. How do they identify themselves? They use IP addresses: a unique address that electronic devices can use to identify and communicate with each other on a computer network utilizing the Internet Protocol standard (IP).

23. University of Khartoum IP Addresses (2) IP addresses come in two versions:

24. University of Khartoum IP Addresses (3) The first major version of addressing structure is referred to as Internet Protocol Version 4 (IPv4). IPv4 is a data-oriented protocol to be used on a packet switched internetwork. IPv4 uses 32-bit (4-byte) addresses, which limits the address space to 4,294,967,296 (2^32) possible unique addresses. However, IPv4 reserves some addresses for special purposes such as private networks (~18 million addresses) or multicast addresses (~270 million addresses). This reduces the number of addresses that can be allocated as public Internet addresses.

25. University of Khartoum IP Addresses (4) An IP address does not always uniquely identify a particular device – it is simply a locator. There are both dynamic (DHCP – dynamic host configuration protocol) and static (manually assigned) IP addresses. Not every device needs a unique, global IP address – can you think of an example? Any thoughts on how you could have devices with local IP addresses and still have them interact with devices on the global internet?

26. University of Khartoum Summary