CVEV 118/698CVEV 118/698 InternetInternet

Lecture 1Lecture 1

Prof. Mounir MabsoutProf. Mounir MabsoutElsa SulukdjianElsa SulukdjianWalid El AsmarWalid El Asmar

1957, USSR launches the first 1957, USSR launches the first artificial satellite called Sputnik I.artificial satellite called Sputnik I.

1958, President Eisenhower creates 1958, President Eisenhower creates the the Advanced Research Project Advanced Research Project AgencyAgency (ARPA) inside the Pentagon. (ARPA) inside the Pentagon.

ARPAARPA’s role is to initiate and fund ’s role is to initiate and fund high-tech research projects.high-tech research projects.

HistoryHistory

1962, 1962, Joseph LickliderJoseph Licklider and and Wesley ClarkWesley Clark publish "publish "On-Line Man-Computer On-Line Man-Computer CommunicationCommunication“.“.

In this visionary paper, the authors described how In this visionary paper, the authors described how the spread of programs and information among a the spread of programs and information among a large number of computers connected by a large number of computers connected by a universal networkuniversal network would create a system more would create a system more powerful than could be built by any organization.powerful than could be built by any organization.

Immediately interested by this idea, the ARPA Immediately interested by this idea, the ARPA chooses Licklider to head the chooses Licklider to head the Information Information Processing Techniques OfficeProcessing Techniques Office (IPTO), created (IPTO), created in October 1962.in October 1962.

History (cont’d)History (cont’d)

Technical InnovationsTechnical Innovations

Two technical innovations were Two technical innovations were necessary to enhance the development necessary to enhance the development this network technology:this network technology:

– The The Packet Switching Packet Switching concept, concept, developed independently by developed independently by Paul Paul BaranBaran (RAND)(RAND) and and Leonard Leonard Kleinrock (MIT). Kleinrock (MIT).

– The The Distributed NetworkDistributed Network architecture, studied by architecture, studied by Paul BaranPaul Baran..

Packet SwitchingPacket Switching In early 60’s, data transmission methods In early 60’s, data transmission methods

used in telecom were very inefficient. used in telecom were very inefficient.

Data was sent from a pole to another in one Data was sent from a pole to another in one batch, through analog circuits.batch, through analog circuits.

The line between the two poles had to The line between the two poles had to remain open throughout the time of remain open throughout the time of transmission. transmission.

Any error would alter the integrity of the Any error would alter the integrity of the whole message, and require to restart the whole message, and require to restart the transmission process.transmission process.

Packet Switching Packet Switching (cont’d)(cont’d)

The concept, proposed by Baran and The concept, proposed by Baran and Kleinrock, consists of dividing each message Kleinrock, consists of dividing each message into into several independent packetsseveral independent packets..

Each packet can travel along a Each packet can travel along a different different pathpath of the network, through intermediary of the network, through intermediary nodes.nodes.

Upon arrival to the destination of all Upon arrival to the destination of all packets, the message is finally reassembled.packets, the message is finally reassembled.

Communication is made digital.Communication is made digital.

The NetworkThe Network Paul Baran compared three network architectures:Paul Baran compared three network architectures:

– The The centralized networkcentralized network, where all hosts are , where all hosts are directly connected to a central unit.directly connected to a central unit.

– The The decentralized networkdecentralized network, with several super-, with several super-nodes, each taking care of a few hosts. nodes, each taking care of a few hosts.

– The The distributed networkdistributed network, where there would be , where there would be NO central authority.NO central authority. All nodes, now of equal All nodes, now of equal status, become potential relays in the transmission status, become potential relays in the transmission of an information.of an information.

The Network (cont’d)The Network (cont’d) The The distributed networkdistributed network itself is assumed to be itself is assumed to be

unreliableunreliable at all times. at all times.

Every node would be Every node would be equal in statusequal in status to all other to all other nodes of the network, with its own authority to nodes of the network, with its own authority to originateoriginate, , passpass and and receivereceive messages. messages.

A packet sent would be tossed from node to node like A packet sent would be tossed from node to node like a hot potato, more or less in the direction of its a hot potato, more or less in the direction of its destination.destination.

This transmission process might first appear very This transmission process might first appear very hazardous and inefficient. hazardous and inefficient.

However, even if big parts of the network were blown However, even if big parts of the network were blown away, the packets would still stay airborne, and wind away, the packets would still stay airborne, and wind their way to their destination, through whatever their way to their destination, through whatever nodes happened to survive.nodes happened to survive.

ARPAnet on the way !ARPAnet on the way ! In 1966, the In 1966, the packet switching packet switching had been successfully had been successfully

tested, and the concept of a tested, and the concept of a distributed network distributed network adopted.adopted.

The IPTO, under the direction of The IPTO, under the direction of Robert TaylorRobert Taylor, , allocated major funds to launch the network project allocated major funds to launch the network project that would lead to the creation of the that would lead to the creation of the ArpanetArpanet. . Lawrence RobertsLawrence Roberts is chosen as the head of the team. is chosen as the head of the team.

At the very early conceptual stage, the project had At the very early conceptual stage, the project had been oriented toward the creation of a been oriented toward the creation of a military military networknetwork that could survive that could survive partial damagepartial damage, after an , after an enemy attack. enemy attack.

However, the military side was never predominant However, the military side was never predominant during the development of the network. Although it during the development of the network. Although it was financed by the Pentagon, the Arpanet was never was financed by the Pentagon, the Arpanet was never “classified”.“classified”.

ARPAnet on the way !ARPAnet on the way ! 1969, Arpanet is finally functional, as four 1969, Arpanet is finally functional, as four

poles are connected in a network: UC-Los poles are connected in a network: UC-Los Angeles, the Stanford Research Institute, UC-Angeles, the Stanford Research Institute, UC-Santa Barbara and The University of Utah.Santa Barbara and The University of Utah.

1970, the Network Control Protocol (NCP) 1970, the Network Control Protocol (NCP) developed by the Network Working Group developed by the Network Working Group (NWG) is ready.(NWG) is ready.

As the project expands, new protocols (TCP/IP As the project expands, new protocols (TCP/IP replacing NCP), and new applications (Telnet, replacing NCP), and new applications (Telnet, FTP, etc…) are developed.FTP, etc…) are developed.

1975, divides the network in two: a public 1975, divides the network in two: a public part (Arpanet) and a military part (Milnet).part (Arpanet) and a military part (Milnet).

Internet on the way !Internet on the way ! In the 70’s, other networks than Arpanet develop. In the 70’s, other networks than Arpanet develop.

1981, the 1981, the National Science FoundationNational Science Foundation (NSF) initiates (NSF) initiates the idea of using the TCP/IP protocol with the regular the idea of using the TCP/IP protocol with the regular telephone connection.telephone connection.

1985, the 1985, the NSFnetNSFnet is created, connecting first the whole is created, connecting first the whole American scientific community, to a single backbone. American scientific community, to a single backbone.

Progressively, many countries connect to NSFnet starting Progressively, many countries connect to NSFnet starting from Canada and northern European countries.from Canada and northern European countries.

NSF encourages the interconnection of all existing NSF encourages the interconnection of all existing networks. networks.

Private clients start financing their own connection to the Private clients start financing their own connection to the network. network.

1990, the first internet provider is born: “The World”.1990, the first internet provider is born: “The World”.

What is Internet ?What is Internet ? The word “The word “InternetInternet” might appear a bit vague, it ” might appear a bit vague, it

refers to:refers to:– Physical links and network routers.Physical links and network routers.– Shared Resources.Shared Resources.– Transmission Protocols.Transmission Protocols.

Internet provides with several Internet provides with several servicesservices::– The The Electronic MailElectronic Mail to send messages. to send messages.– The The World Wide WebWorld Wide Web to access/share to access/share

information.information.– NewsGroupsNewsGroups or Discussion Groups. or Discussion Groups. – TheThe File Transfer File Transfer..– TelnetTelnet to connect to distant machines. to connect to distant machines. – The The Internet Relay ChatInternet Relay Chat (IRC) (IRC)

Get ConnectedGet Connected Technically, all that is needed to connect to Technically, all that is needed to connect to

internet is a computer, a communication internet is a computer, a communication device (I.e. modem) and a communication device (I.e. modem) and a communication software (TCP/IP protocol).software (TCP/IP protocol).

You can be part of a Local Area Network You can be part of a Local Area Network (LAN); or connect via a Provider.(LAN); or connect via a Provider.

Communication on internet is based on a Communication on internet is based on a ““client-serverclient-server” model.” model.

The The clientclient program formulates a specific program formulates a specific request, carried out by the request, carried out by the serverserver upon upon reception.reception.

Get ConnectedGet Connected

IP AddressesIP Addresses How to find a specific machine on the net to How to find a specific machine on the net to

address a certain request ?address a certain request ?

Each machine connected to internet has a Each machine connected to internet has a unique IP addressunique IP address, just like a phone number. , just like a phone number. (IPv4)(IPv4)

The IP address is a number of The IP address is a number of 4 × 8 bits4 × 8 bits. I.e.:. I.e.:IP = 11001010 00001111 10101010 IP = 11001010 00001111 10101010

0000000100000001Corresponding in decimal to 202.15.170.1Corresponding in decimal to 202.15.170.1

Theoretically there are 256Theoretically there are 25644 possible IP possible IP addresses.addresses.

Practically the number of arrangements is much Practically the number of arrangements is much smaller, due to conventional restrictions, smaller, due to conventional restrictions, technical purposes and even past waste.technical purposes and even past waste.

IP Addresses (Cont’d)IP Addresses (Cont’d) IP addresses are organized into four different classes, IP addresses are organized into four different classes,

each corresponding to a certain type of network:each corresponding to a certain type of network:– Class A, where the most significant bit (MSB) is 0, Class A, where the most significant bit (MSB) is 0,

and the seven next bits are fixed: and the seven next bits are fixed: 0xxxxxxx yyyyyyyy… (I.e. IP < 127…)0xxxxxxx yyyyyyyy… (I.e. IP < 127…)

– Class B, where the two MSB are 10, and the Class B, where the two MSB are 10, and the fourteen next bits are fixed: fourteen next bits are fixed: 10xxxxxx xxxxxxxx yyyyyyyy… (I.e. IP < 192…)10xxxxxx xxxxxxxx yyyyyyyy… (I.e. IP < 192…)

– Class C, where the three MSB are 110, and the Class C, where the three MSB are 110, and the twenty-one next bits are fixed: twenty-one next bits are fixed: 110xxxxx xxxxxxxx xxxxxxxx yyyyyyyy… (I.e. IP < 110xxxxx xxxxxxxx xxxxxxxx yyyyyyyy… (I.e. IP <

224…)224…)– Class DClass D

IPv4 is nearly saturated. IPv6 is a comparable system IPv4 is nearly saturated. IPv6 is a comparable system that relies 32 bytes addresses.that relies 32 bytes addresses.

ProtocolsProtocols A packet is not only modeled in function of the A packet is not only modeled in function of the

data to be transmitted and the destination IP data to be transmitted and the destination IP address.address.

ProtocolsProtocols are communication standards. They are communication standards. They are organized in a are organized in a Layer ModelLayer Model, where each , where each layer is independent.layer is independent.

Before being sent, a packet will pass through Before being sent, a packet will pass through the layer model, where each protocol will the layer model, where each protocol will append to it a certain append to it a certain headerheader.(.(EncapsulationEncapsulation process)process)

The headers will contain information on the The headers will contain information on the packet’s application, transport, command, etc… packet’s application, transport, command, etc…

Upon reception of a packet, Upon reception of a packet, reading/understanding the information starts reading/understanding the information starts with decoding the headers.with decoding the headers.

EncapsulationEncapsulation

Application Data

TCP hdrIP hdr Application Data

Application DataTCP hdr

IP hdr Application DataTCP hdrFrame hdr

TCP/IP Model

Application

Transport

InternetNetworkAccess

IP and TCP/IPIP and TCP/IP The The IPIP (Internet Protocol) is a fundamental part in (Internet Protocol) is a fundamental part in

the transmission process. the transmission process.

Yet, Yet, IPIP is only involved at the emission level, and is only involved at the emission level, and ignores all the rest of the transmission process. ignores all the rest of the transmission process. (reception, integrity and coherence of information, (reception, integrity and coherence of information, etc…)etc…)

The The TCPTCP (Transmission Control Protocol) completes (Transmission Control Protocol) completes IP by:IP by:– Establishing a connection.Establishing a connection.– Sequencing the packets.Sequencing the packets.– Controlling the flux.Controlling the flux.– Managing errors.Managing errors.

The notation The notation TCP/IPTCP/IP really means “ really means “TCP over IPTCP over IP” in ” in reference to the protocol layer model.reference to the protocol layer model.

The Domain Name The Domain Name SystemSystem

For practical reasons, there exists a For practical reasons, there exists a transcription system called transcription system called DNSDNS (Domain Name (Domain Name System), that translates IP addresses into text System), that translates IP addresses into text addresses.addresses.

Usually an address contains a Usually an address contains a NameName, and a , and a Domain Domain that can be generic (that can be generic (comcom,, net net,, org org,…), ,…), or specific to a country (I.e. or specific to a country (I.e. lblb).).

A A URLURL (Uniform Resource Locator) should (Uniform Resource Locator) should always start with the following structure:always start with the following structure:

Protocol://serverProtocol://serveri.e.:i.e.: http://www.aub.edu.lbhttp://www.aub.edu.lb

The protocol can be http, ftp, etc… in reference The protocol can be http, ftp, etc… in reference to a certain service.to a certain service.

Who Controls Internet ?Who Controls Internet ? Well, nobody really does.Well, nobody really does.

Still some benevolent groups inside the ISOC try to Still some benevolent groups inside the ISOC try to manage its general technical orientation.manage its general technical orientation.

TheThe ISOC ISOC (Internet Society), entirely composed of (Internet Society), entirely composed of benevolent, is in charge of the administration of the benevolent, is in charge of the administration of the net.net.

The The IETFIETF (Internet Engineering Task Force) (Internet Engineering Task Force) regularly produce papers simply exposing some regularly produce papers simply exposing some critical observations on the net, or proposing to the critical observations on the net, or proposing to the IABIAB and the users new standards and technical and the users new standards and technical innovations.innovations.

The The IABIAB (Internet Architecture Board) meets to (Internet Architecture Board) meets to adopt the proposed standards, and approve the adopt the proposed standards, and approve the allocation of new addresses and resources.allocation of new addresses and resources.

Who Controls Internet ?Who Controls Internet ?

What’s Next ?What’s Next ?

Internet Programming…Internet Programming…