Human-Computer Interface Course 4

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

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 – Project success=> handed to the Defense Communication Agency

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

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

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.

What is Internet Internet Structure

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

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)

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

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

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.

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

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

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.

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

Routing Internet Routing

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.

ISPs and Internet connection