Kerio Tech Firewall6 - Manual (Page 395)

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will be redirected to this host. Packets that do not match with any record in the
NAT table will be dropped.
• destination address translation (Destination NAT, DNAT, it is also called port
mapping) — is used to enable services in the local network from the Internet. If
any packet incoming from the Internet meets certain requirements, its IP address
will be substituted by the IP address of the local host where the service is running
and the packet is sent to this host.
The NAT technology enables connection from local networks to the Internet using a single
IP address. All hosts within the local network can access the Internet directly as if they
were on a public network (certain limitations are applied). Services running on local hosts
can be mapped to the public IP address.
Detailed description (in English) can be found for example at Wikipedia .
Network adapter
The equipment that connects hosts to a traffic medium. It can be represented by an
Ethernet adapter, TokenRing adapter, by a modem, etc. Network adapters are used by
hosts to send and receive packets. They are also referred to throughout this document
as a network interface.
P2P network
Peer-to-Peer (P2P) networks are world-wide distributed systems, where each node can
represent both a client and a server. These networks are used for sharing of big volumes
of data (this sharing is mostly illegal). DirectConnect and Kazaa are the most popular
ones.
Packet
Basic data unit transmitted via computer networks. Packets consist of a header which
include essential data (i.e. source and destination IP address, protocol type, etc.) and of
the data body,. Data transmitted via networks is divided into small segments, or packets.
If an error is detected in any packet or a packet is lost, it is not necessary to repeat the
entire transmission process, only the particular packet will be re-sent.
Policy routing
Advanced routing technology using additional information apart from IP addresses, such
as source IP address, protocols etc.
See also routing table.
POP3
Post Office Protocol is an email accessing protocol that allows users to download mes-
sages from a server to a local disk. It is suitable for clients who don’t have a permanent
connection to the Internet.
Port
16-bit number (1-65535) used by TCP and UDP for application (services) identification on
a given computer. More than one application can be run at a host simultaneously (e.g.
WWW server, mail client, FTP client, etc.). Each application is identified by a port number.