Início da Internet• Antes da Internet (~1960)

– Primeiros sistemas computacionais consistiam de grandes sistemas para processamento de dados

– Arquiteturas e protocolos de redes proprietários eram usados– Infraestruturas de redes eram estendidas com o uso de

componentes similares– Não havia interesse em interoperabilidade

• Cooperação entre instituições de pesquisa– Conduzida pela “Advanced Research Projects Agency (ARPA)

Department of Defense (DoD)– Usuários em diferentes organizações necessitavam

compartilhar informações– Confiabilidade (Reliability) necessária por conta de possíveis

falhas em equipamentos– Advanced Research Projects Agency Network (ARPANET)

ARPANET• Primeiro Esboço da ARPANET• Initial ARPANET consisted of:– Interface message processors (IMP)– Host computers connected to IMP via serial line– Host-to-host protocol called NetworkControl Protocol (NCP)

ARPANET• Em 1969 a ARPA inicia uma “experimental packet

radio network” com a University of Hawaii.• Esta rede ALOHANET conectava as ilhas do Havai

mas era vista pela ARPANET como um simples terminal.

• Em paralelo outras redes baseadas em pacotes estavam sendo desenvolvidas na Europa

• Em 1972 o International Network Working Group (INWG) iniciou os trabalhos para conectar as diversas redes para criar uma rede global.

• Essa rede utilizaria rádio e satélite para com protocolos diferentes específicos para cada necessidade da rede.

O Nascimento da Internet• In 1980, the U.S. military adopted TCP/IP as

a networking standard• A "flag day" transition from NCP to TCP/IP

that took place on January 1, 1983• By 1985, the ARPANET was heavily utilized

and the National Science Foundation initiated the development of NSFNET

• In 1990, commercial agencies and other general purpose companies required networking, giving rise to Internet service providers (ISPs)

O Nascimento da Internet• The INWG managed the development of

Internet and TCP/IP related protocols. From its very beginning, anyone was allowed to participate in the process merely by generating ideas for protocols to use on these emerging networks The RFC or Request for Comments.

• The INWG evolved over the years into the Internet Engineering Task Force (IETF),

• IETF is now the standards body for TCP/IP and related protocols

Internet Traffic

Secção 2 – Componentes da Internet

• Simple Definition– The Internet is built with computers that are

connected by wires. Each wire serves as a way to exchange information between the two computers that are connected.

• Practical Definition– The Internet consists of many distributed network

architectures that are operated by many commercial organizations (ISPs) connected via major network exchange points as well as direct network interconnections [Internet Routing Architectures, 2nd Edition, Sam Halibi], all using the IP.

Home to Local ISP Connections

ISP with POPs in Different Cities

IXPs – Internet Exchange PointPOP – Point of Presence

Nem todos os POPs precisam estar conectados diretamenteAos Providores de conteudo

Slide

Com os IXPs tráfego entre dois ISPs pode ser comutadolocalmente.

IXPs – Internet Exchange PointPOP – Point of Presence

Mini Overview TCP/IP• IP – Internet Protocol defines an

unique IP address to every single computer.

• The distribution of IP addresses is supervised by a centralized authority known as the Internet Assigned Numbers Authority (IANA).

• The distribution is delegated to the Regional Internet Registry (RIR) all around the world.

Regional Internet Registry agents allocate IP addresses

Seção 3 – How the Internet Works – TCP/IP Layering

Encapsulation Process

FCS - Frame Check Sequence

The Open Systems Interconnection (OSI) reference model

Layer 1

Layer 2

Layer 7

Layer 3

7450 ESS Family

IPv4 Packet Header

IPv4 Packet Header• IHL — IP header length. The number of 32-bit words that form the header. The value is usually

five.• TOS — Type of Service is also known as the Differentiated Services Code Point (DSCP). The TOS

byte can be used to specify Quality of Service parameters for the packet, but this is often not respected by the

• network.• Total Length — The combined length of the header and the data, in bytes• Identification — Together with the source address, this 16-bit number uniquely identifies the

packet. The number is used during the reassembly of fragmented datagrams.• Flags — Three bits used for the fragmentation of packets. The first bit is unused. The second

indicates DF, or don't fragment, meaning that the packet must be discarded instead of fragmented. The third indicates MF, or more fragments, indicating that this is not the last fragment

• Fragment Offset — A value that indicates which fragment of the original packet this corresponds to. This is used during the reassembly of fragmented datagrams.

• Time To Live (TTL) — Number of hops or links that the packet may be routed over, decremented by each router (used to prevent accidental routing loops)

• Protocol — Identifier that indicates the type of transport packet being carried (for example, 1 = ICMP, 2= IGMP, 6 = TCP, 17 = UDP)

• Header Checksum —1s complement checksum that is inserted by the sender and updated whenever the packet header is modified by a router. Used to detect errors introduced into the IP header. Packets with an invalid header checksum are discarded by all nodes in an IP network.

• Source IP Address — IP address of the original sender of the packet• Destination IP Address — IP address of the final destination of the packet• Options — Not often used. However when the options are used, the IP header length is greater than

five 32-bit words to indicate the size of the options field.

IPv4 Address• The unique L3 identifier of computers,

routers, and other devices in an IP network• The 32-bit address is expressed in dotted-

decimal format, with each octet separated by a period

• IP address example: 192.168.2.100• Binary equivalent:

11000000.10101000.00000010.01100100• Ou apenas

11000000101010000000001001100100

IP Address Components

IP Address Classes

IP Address Classes• Class A (1 to 126) — A Class A network has an 8-bit network prefix and the

highest-order bit is always set to 0. This allows up to 126 networks to be defined because, 2 of the networks are reserved. The 0.0.0.0 network is reserved for default routes. The 127.0.0.0 network is reserved for loopback functions.

• Class B (128 to 191) — A Class B network has a 16-bit network prefix and the two highest-order bits are always set to binary 10. Up to 16 384 networks can be defined.

• Class C (192 to 223) — A Class C network has a 24-bit network prefix and the three highest-order bits are always set to binary 110. Up to 2 097 152 networks can be defined.

• Class D (224 to 239) — Class D is used for multicast addresses in applications such as OSPF.

• Class E (240 to 255) — Class E is reserved.