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Tracelink User Manual 20
5.3 Internet Protocol
Once the network has been established, and the IP numbers have been assigned,
data can be transacted over a network with one of several protocols. By far the most
prevalent protocol is the Transmission Control Protocol (TCP), which runs on top of
the Internet Protocol in what is collectively known as the TCP/IP protocol. The TCP/IP
protocol was developed by the Department of Defense to connect different computers
from different vendors by a “network of networks,” which has become what is known
as the Internet today.
The primary purpose of the TCP/IP protocol was to prevent a complete network
outage in the case of a nuclear attack, by automatically rerouting data traffic through
the functioning part of the network. As such, the TCP/IP mechanism guaranteed
delivery of data packets by introducing a system of acknowledgements and sequence
numbers for the data packets. This mechanism, while good for transacting large
amounts of data (such as email or file transfers), is unsuitable in the real-time type
environment in which the Tracelink operates. Because the Tracelink needs to transact
data as quickly as possible to the target, it takes advantage of TCP/IP’s alternative,
the UDP/IP protocol.
Unlike TCP/IP, the UDP/IP protocol is a connectionless, single-packet protocol that
sends short data packets at the expense of not guaranteeing their delivery. This
makes the UDP/IP protocol efficient in real-time applications such as broadcasting
video over the Internet, where the occasional loss of a frame of data is not going to
hamper the overall viewing experience. Left unmodified, the UDP/IP, with its lack of
guarantees for packet delivery, would be unusable in an environment where the
delivery of a single byte of data needs to be guaranteed. The Tracelink firmware adds
mechanisms to the UDP/IP protocol, without affecting its underlying efficiency, to
guarantee delivery of data packets.
5.4 Connecting The Tracelink Device
There are two methods for establishing a connection between a Tracelink and a PC
with an Ethernet cable. The most basic method is to connect the Tracelink directly to a
PC, via a cross-over Ethernet cable. However, the more common method is to place
the Tracelink and the PC on the same network through a Hub.
5.4.1 Connecting the Tracelink to the PC over a network:
The Tracelink was intended for use on a network of multiple computers (and other
Tracelinks). There are many possible network configurations, and to describe them all
is beyond the scope of this document. However, most configurations are a