SMC Networks BR14VPN - annexe 3 Manual page 75

incoming data matches the predefined set of characteristics the incoming traffic is allowed. If no
match is found the incoming traffic is discarded.
Subnet Mask - A subnet mask, which may be a part of the TCP/IP information provided by your
ISP, is a set of four numbers configured like an IP address. It is used to create IP address
numbers used only within a particular network (as opposed to valid IP address numbers
recognized by the Internet.
TCP/IP - Transmission Control Protocol/Internet Protocol. This is the standard protocol for data
transmission over the Internet.
TCP - Transmission Control Protocol - TCP and UDP (User Datagram Protocol) are the two
transport protocols in TCP/IP. TCP ensures that a message is sent accurately and in its entirety.
However, for real-time voice and video, there is really no time or reason to correct errors, and
UDP is used instead.
UDP - User Datagram Protocol - A protocol within the TCP/IP protocol suite that is used in place
of TCP when a reliable delivery is not required. For example, UDP is used for real-time audio and
video traffic where lost packets are simply ignored, because there is no time to retransmit. If
UDP is used and a reliable delivery is required, packet sequence checking and error notification
must be written into the applications.
VPN - Virtual Private Network that actually exists within a public network. This consists of a point-
to-point tunnel through which users can send and receive data. The data packets are encrypted
to provide for a true private connection to the endpoint (i.e. - corporate network). These packets
cannot be decrypted without the correct encryption keys. Once the VPN tunnel is established, the
client machine is authenticated and registered on the network. Given the proper privileges, it can
then communicate directly with other machines as if it were actually on that local network.
70