Camada de rede

Camada de Rede
Protocolos da Camada de Rede: IP v4 (ARP); IP v6 (ND); ICMP NAT – Network Address Translation Protocolos de Routing: RIP; OSPF Comandos: Ping; Traceroute; Route Print

Novembro, 2010

•

Fonte: acetatos Prof. Manuel Ricardo - FEUP

NAT

•

NAT/PAT
– By using a different port number for each user, the NAT device knows which client PC to route the incoming packets to.

NAT
• Network address translation
– From Wikipedia, the free encyclopedia

•

In computer networking, network address translation (NAT) is the process of modifying network address information in datagram packet headers while in transit across a traffic routing device for the purpose of remapping a given address space into another.
Most often today, NAT is used in conjunction with network masquerading (or IP masquerading) which is a technique that hides an entire address space, usually consisting of private network addresses (RFC 1918), behind a single IP address in another, often public address space. This mechanism is implemented in a routing device that uses stateful translation tables to map the "hidden" addresses into a single address and then rewrites the outgoing Internet Protocol (IP) packets on exit so that they appear to originate from the router. In the reverse communications path, responses are mapped back to the originating IP address using the rules ("state") stored in the translation tables. The translation table rules established in this fashion are flushed after a short period without new traffic refreshing their state. As described, the method enables communication through the router only when the conversation originates in the masqueraded network, since this establishes the translation tables. For example, a web browser in the masqueraded network can browse a website outside, but a web browser outside could not browse a web site in the masqueraded network. However, most NAT devices today allow the network