Network Address Translation (NAT)

A mechanism for converting the internal private IP addresses found in packet headers into public IP addresses and port numbers for transmission over the Internet. PAT supports a many-to-one mapping of internal to external IP addresses by using ports.
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A piece of a packet. When a router is forwarding an IP packet to a network with a Maximum Transmission Unit smaller than the packet size, it is forced to break up that packet into multiple fragments. These fragments will be reassembled by the IP layer at the destination host. When a network receives a packet larger than its maximum allowable packet size, it breaks it up into two or more fragments. These fragments are each assigned a size (corresponding to the length of the fragment) and an offset (corresponding to the starting location of the fragment).
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A network connection established between two systems over an existing private or public network. A VPN provides confidentiality and integrity for network traffic through the use of encryption. A secure private network that uses the public telecommunications infrastructure to transmit data. In contrast to a much more expensive system of owned or leased lines that can only be used by one company, VPNs are used by enterprises for both extranets and wide are intranets. Using encryption and authentication, a VPN encrypts all data that passes between two Internet points, maintaining privacy and security. Protected information system link utilizing tunneling, security controls (. See information assurance), and endpoint address translation giving the impression of a dedicated line.
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Highspeed switch that forwards packets between datalink segments. Most LAN switches forward traffic based on MAC addresses. This variety of LAN switch is sometimes called a frame switch. LAN switches are often categorized according to the method they use to forward traffic: cutthrough packet switching or storeandforward packet switching. Multilayer switches are an intelligent subset of LAN switches. Compare with multilayer switch. See also cutthrough packet switching, storeandforward packet switching.
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A mode of IPSec when used in a VPN. In tunnel mode, the entire IP packet is encrypted and a new header is added to the packet to govern transmission through the tunnel. An IPSec protocol used with ESP in which the header and contents of an IP packet are encrypted and encapsulated prior to transmission, and a new IP header is added.
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