CVEV 118/698 Internet

1. CVEV 118/698Internet Lecture 1 Prof. Mounir Mabsout Elsa Sulukdjian Walid El Asmar

2. History • 1957, USSR launches the first artificial satellite called Sputnik I. • 1958, President Eisenhower creates the Advanced Research Project Agency (ARPA) inside the Pentagon. • ARPA’s role is to initiate and fund high-tech research projects.

3. History (cont’d) • 1962, Joseph Licklider and Wesley Clark publish "On-Line Man-Computer Communication“. • In this visionary paper, the authors described how the spread of programs and information among a large number of computers connected by a universal network would create a system more powerful than could be built by any organization. • Immediately interested by this idea, the ARPA chooses Licklider to head the Information Processing Techniques Office (IPTO), created in October 1962.

4. Technical Innovations • Two technical innovations were necessary to enhance the development this network technology: • The Packet Switching concept, developed independently by Paul Baran(RAND) and Leonard Kleinrock (MIT). • The Distributed Network architecture, studied by Paul Baran.

5. Packet Switching • In early 60’s, data transmission methods used in telecom were very inefficient. • Data was sent from a pole to another in one batch, through analog circuits. • The line between the two poles had to remain open throughout the time of transmission. • Any error would alter the integrity of the whole message, and require to restart the transmission process.

6. Packet Switching (cont’d) • The concept, proposed by Baran and Kleinrock, consists of dividing each message into several independent packets. • Each packet can travel along a different path of the network, through intermediary nodes. • Upon arrival to the destination of all packets, the message is finally reassembled. • Communication is made digital.

7. The Network • Paul Baran compared three network architectures: • The centralized network, where all hosts are directly connected to a central unit. • The decentralized network, with several super-nodes, each taking care of a few hosts. • The distributed network, where there would be NO central authority. All nodes, now of equal status, become potential relays in the transmission of an information.

8. The Network (cont’d) • The distributed network itself is assumed to be unreliable at all times. • Every node would be equal in status to all other nodes of the network, with its own authority to originate, pass and receive messages. • A packet sent would be tossed from node to node like a hot potato, more or less in the direction of its destination. • This transmission process might first appear very hazardous and inefficient. • However, even if big parts of the network were blown away, the packets would still stay airborne, and wind their way to their destination, through whatever nodes happened to survive.

9. ARPAnet on the way ! • In 1966, the packet switching had been successfully tested, and the concept of a distributed network adopted. • The IPTO, under the direction of Robert Taylor, allocated major funds to launch the network project that would lead to the creation of the Arpanet. Lawrence Roberts is chosen as the head of the team. • At the very early conceptual stage, the project had been oriented toward the creation of a military network that could survive partial damage, after an enemy attack. • However, the military side was never predominant during the development of the network. Although it was financed by the Pentagon, the Arpanet was never “classified”.

10. ARPAnet on the way ! • 1969, Arpanet is finally functional, as four poles are connected in a network: UC-Los Angeles, the Stanford Research Institute, UC-Santa Barbara and The University of Utah. • 1970, the Network Control Protocol (NCP) developed by the Network Working Group (NWG) is ready. • As the project expands, new protocols (TCP/IP replacing NCP), and new applications (Telnet, FTP, etc…) are developed. • 1975, divides the network in two: a public part (Arpanet) and a military part (Milnet).

11. Internet on the way ! • In the 70’s, other networks than Arpanet develop. • 1981, the National Science Foundation (NSF) initiates the idea of using the TCP/IP protocol with the regular telephone connection. • 1985, the NSFnet is created, connecting first the whole American scientific community, to a single backbone. • Progressively, many countries connect to NSFnet starting from Canada and northern European countries. • NSF encourages the interconnection of all existing networks. • Private clients start financing their own connection to the network. • 1990, the first internet provider is born: “The World”.

12. What is Internet ? • The word “Internet” might appear a bit vague, it refers to: • Physical links and network routers. • Shared Resources. • Transmission Protocols. • Internet provides with several services: • The Electronic Mail to send messages. • The World Wide Web to access/share information. • NewsGroups or Discussion Groups. • The File Transfer. • Telnet to connect to distant machines. • The Internet Relay Chat (IRC)

13. Get Connected • Technically, all that is needed to connect to internet is a computer, a communication device (I.e. modem) and a communication software (TCP/IP protocol). • You can be part of a Local Area Network (LAN); or connect via a Provider. • Communication on internet is based on a “client-server” model. • The client program formulates a specific request, carried out by the server upon reception.

14. Get Connected

15. IP Addresses • How to find a specific machine on the net to address a certain request ? • Each machine connected to internet has a unique IP address, just like a phone number. (IPv4) • The IP address is a number of 4 × 8 bits. I.e.: IP = 11001010 00001111 10101010 00000001 Corresponding in decimal to 202.15.170.1 • Theoretically there are 2564 possible IP addresses. • Practically the number of arrangements is much smaller, due to conventional restrictions, technical purposes and even past waste.

16. IP Addresses (Cont’d) • IP addresses are organized into four different classes, each corresponding to a certain type of network: • Class A, where the most significant bit (MSB) is 0, and the seven next bits are fixed: 0xxxxxxx yyyyyyyy… (I.e. IP < 127…) • Class B, where the two MSB are 10, and the fourteen next bits are fixed: 10xxxxxx xxxxxxxx yyyyyyyy… (I.e. IP < 192…) • Class C, where the three MSB are 110, and the twenty-one next bits are fixed: 110xxxxx xxxxxxxx xxxxxxxx yyyyyyyy… (I.e. IP < 224…) • Class D • IPv4 is nearly saturated. IPv6 is a comparable system that relies 32 bytes addresses.

17. Protocols • A packet is not only modeled in function of the data to be transmitted and the destination IP address. • Protocols are communication standards. They are organized in a Layer Model, where each layer is independent. • Before being sent, a packet will pass through the layer model, where each protocol will append to it a certain header.(Encapsulation process) • The headers will contain information on the packet’s application, transport, command, etc… • Upon reception of a packet, reading/understanding the information starts with decoding the headers.

18. Application Transport Internet Application Data Network Access TCP hdr Application Data IP hdr TCP hdr Application Data TCP/IP Model Frame hdr IP hdr TCP hdr Application Data Encapsulation

19. IP and TCP/IP • The IP (Internet Protocol) is a fundamental part in the transmission process. • Yet, IP is only involved at the emission level, and ignores all the rest of the transmission process. (reception, integrity and coherence of information, etc…) • The TCP (Transmission Control Protocol) completes IP by: • Establishing a connection. • Sequencing the packets. • Controlling the flux. • Managing errors. • The notation TCP/IP really means “TCP over IP” in reference to the protocol layer model.

20. The Domain Name System • For practical reasons, there exists a transcription system called DNS (Domain Name System), that translates IP addresses into text addresses. • Usually an address contains a Name, and a Domain that can be generic (com, net, org,…), or specific to a country (I.e. lb). • A URL (Uniform Resource Locator) should always start with the following structure: Protocol://server i.e.:http://www.aub.edu.lb • The protocol can be http, ftp, etc… in reference to a certain service.

21. Who Controls Internet ? • Well, nobody really does. • Still some benevolent groups inside the ISOC try to manage its general technical orientation. • The ISOC (Internet Society), entirely composed of benevolent, is in charge of the administration of the net. • The IETF (Internet Engineering Task Force) regularly produce papers simply exposing some critical observations on the net, or proposing to the IAB and the users new standards and technical innovations. • The IAB (Internet Architecture Board) meets to adopt the proposed standards, and approve the allocation of new addresses and resources.

22. Who Controls Internet ?

23. What’s Next ? • Internet Programming…