Redes - Capitulo 5: OSI/ISO

Capitulo 5: OSI/ISO

Com permissão do autor Everson Santos Araujo, anexo uma clara definição do funcionamento do modelo OSI/ISO

Definições:

ISO: International Organization for Standardization, is the world’s largest developer of voluntary International Standards. International Standards give state of the art specifications for products, services and good practice, helping to make industry more efficient and effective. Developed through global consensus, they help to break down barriers to international trade.

mod_dosevasive: is an evasive maneuvers module for Apache to provide evasive action in the event of an HTTP DoS or DDoS attack or brute force attack. It is also designed to be a detection and network management tool, and can be easily configured to talk to ipchains, firewalls, routers, and etcetera. mod_dosevasive presently reports abuses via email and syslog facilities.

RFCS: (acrónimo em inglês de Request for Comments), é um documento que descreve os padrões de cada protocolo da Internet previamente a serem considerados um padrão.

Broadcast storm: A broadcast storm occurs when a network system is overwhelmed by continuous multicast or broadcast traffic. When different nodes are sending/broadcasting data over a network link, and the other network devices are rebroadcasting the data back to the network link in response, this will eventually cause the whole network to melt down and lead to the failure of network communication.

There are many reasons a broadcast storm occurs, including poor technology, low port rate switches and improper network configurations.

Spanning Tree Protocol (referido com o acrónimo STP) é um protocolo para equipamentos de rede que permite resolver problemas de loop em redes comutadas cuja topologia introduza anéis nas ligações, auxiliando na melhor performace da rede.

The quality of service (QoS) refers to several related aspects of telephony and computer networks that allow the transport of traffic with special requirements. In particular, much technology has been developed to allow computer networks to become as useful as telephone networks for audio conversations, as well as supporting new applications with even stricter service demands.

ToS (Type of Services ou ToS), trata-se de um campo no cabeçalho IPv4 originalmente e tem sido definida de diferentes maneiras pelas normas (RFC 791, RFC 1122, RFC 1349, RFC 2474 e RFC 3168), hoje definido pelas normas RFC 2474 como (DiffServ) combinando o IPv6, é utilizando para diferenciar o tipo do pacote a ser transportado, classificando-o para que possa ter prioridade em sua transmissão. Seu campo contém oito bits sendo utilizado 6 bits para os serviços diferenciados (Differentiated Services Code Point ou DSCP) e 2 bits para o controle de alertas para congestionamento (Explicit Congestion Notification ou ECN). Mesmo com as mudanças que o ToS vem passando ao longo do tempo hoje se tornado o DiffServ algumas de suas peculiaridades ainda são mantidas devido a compatibilidade de versões anteriores.

CoS, Class of service is a parameter used in data and voice protocols to differentiate the types of payloads contained in the packet being transmitted. The objective of such differentiation is generally associated with assigning priorities to the data payload or access levels to the telephone call.