Network Address Translation translates and IP address used in a network to another IP address known within another network. A NAT table is maintained for global to local and local to mapping of IP?s. NAT can be statically defined or dynamically translate from a pool of addresses. The NAT router is responsible for translating traffic coming and leaving the network. NAT prevents malicious activity initiated by outside hosts from reaching local hosts by being dependent on a machine on the local network to initiate any connection to hosts on the other side of the router.
Flag field: 1 byte: - Indicates frames beginning or end Address field: 1 byte: - Used for broadcast address (destination address) Control field: 1 byte: - Used as a control byte Protocol field: - 1 or 2 bytes: - Setting of protocol in information field (of datagram) Information: - 0 or more bytes: - Datagram (whether it contains data or control information) Padding: - 0 or more bytes: - optional padding FCS: - 2 or more bytes: - error check sum Source: CoolInterview.com