1. Human-Computer Interface Course 4

2. Content History of Internet What is Internet ? Internet Protocols The OSI 7 layers model TCP/IP The World Wide Web Internet Security Mail, WWW, HTTP, FTP, SSL

3. Internet History 1969 – Birth of Internet - DoD project - wartime digital communications. Solution - The Defense Advanced Research Projects Agency (DARPA) launched the DARPA Internet Program 1970 – Infancy – 1 decade of research obscurity. 1975 – Project success=> handed to the Defense Communication Agency

4. Internet History 1980 – Key protocols are stable and used (IP and TCP) 1983 – ARPANET – Internet community dominated by research and military sites. 1983 – 562 ARPANET registered hosts. Unix – the first operating systems implementing Internet protocols. Late 1980 – The PC and LAN Revolution.

5. Internet History 1987 – The first Internet Worm appeared. 1987 – NSFNET – backbone = T1 line connected to 170 small networks at 1.544 Mbps Early 1990 – Internet faces the Address Exhaustion Problem – Solution CIDR = Classless Inter domain routing Mid 1990 – Internet Exponential Growth

6. What is Internet ? Internet = a set of interconnected networks. Backbone = a trunk connecting multiple access points together. Internet communication – follows some predefined rules = communication protocols.

7. What is Internet Internet Structure

8. The Internet Protocols Protocol = "a formal description of message formats and the rules two or more machines must follow to exchange those messages." Internet communicates using multiple protocols at different levels: IP, TCP, UDP DNS, FTP, WWW, etc

9. Protocol Layering Simplifies network designs by dividing it in functional layers and assigning protocols to perform each layer's task. Layering models: The OSI Seven layer model The DoD Network model (original for Internet)

10. Dod Network Model 4 Layers Network access Internet IP Host to host (TCP/UDP) Process

11. The OSI 7 Layer model A ll P eople S eem T o N eed D ata P rocessing

12. The TCP/IP protocol TCP/IP the ARPANET communication protocol. TCP/IP provides: TCP - connection oriented reliable comm. UDP - connectionless unreliable comm. ICMP – error reporting and protocol diagnostic. Tightly integrated into IP.

13. TCP/IP Addressing Each host on the network has a UNIQUE IP address on 32 bits = 4 bytes. Ex: www.cs.ubbcluj.ro - 193.231.20.34www.cs.ubbcluj.ro 4 bytes = 2 32 = 4,294,967,296 Address = Net Part + Host part.

14. IP Address Classes Class A (1 Byte Net Address) => (1=126).x.x.x =>126 class networks with 2 24 -2 hosts each. Class B => (2 bytes Net Address) => (128-191).N.x.x =>16384 Networks with 2 16 -2 hosts. Class C => (3 bytes Net Address)=>(192- 223).N.N.x => networks with 254 hosts. Class D => (Octet 1- 1110) – multicast Class E => (Octet 1- 1111) - Experimental

15. Routing Method for choosing the path of a TCP/IP packet. Implemented as tables Each entry specifies the next hop. Default entry = the next hop for non specified targets. Each network provides a gateway that routes packets.

16. Routing Router = special machine implementing the routing algorithms. Router’s tasks Ensures that information doesn’t go where is not needed. Ensures that information does make it to its destination

17. Routing Internet Routing

18. LAN/WAN/Internet LAN – small area network with reduced routing capabilities. Communication is based on the Ethernet’s broadcast nature. WAN – wide area networks – based on inter- connection of multiple lines over leased lines, Fiber optic, radio links, etc. Provides and requires important routing support in order to function properly.

19. ISPs and Internet connection