26
User Guide
27
others. These applications cannot work when Network Address Translation
(NAT) is enabled. When users send this type of request to your network
via the Internet, the Router will forward those requests to the appropriate
PC. If you need to run applications that require multiple connections,
specify the port normally associated with an application in the “Trigger
Port” fi eld, select the protocol type as TCP or UDP, then enter the public
ports associated with the trigger port to open them for inbound traffi c.
. TCP (Transmission Control Protocol) -
A method (protocol) used along with
the Internet Protocol (Internet Protocol) to send data in the form of message
units between computers over the Internet. While IP takes care of handling
the actual delivery of the data, TCP takes care of keeping track of the
individual units of data (called packets) that a message is divided into for
effi cient routing through the Internet.
. UDP (User Datagram Protocol) -
A communications method (protocol)
that offers a limited amount of service when messages are exchanged
between computers in a network that uses the Internet Protocol (IP). UDP
is an alternative to the TCP and, together with IP, is sometimes referred to
as UDP/IP. Like the Transmission Control Protocol, UDP uses the Internet
Protocol to actually get a data unit (called a datagram) from one computer
to another. Unlike TCP, however, UDP does not provide the service of
dividing a message into packets (datagrams) and reassembling it at the
other end. Specifi cally, UDP doesn’t provide sequencing of the packets
that the data arrives in. This means that the application program that uses
UDP must be able to make sure that the entire message has arrived and is
in the right order. Network applications that want to save processing time
because they have very small data units to exchange (and therefore very
little message reassembling to do) may prefer UDP to TCP.