An Investigation into Transport Protocols and Data Transport ...

A.2. Network Interface Cards 276
Layer 1 propagation.
Similarly, the transport of data also relies upon the co-ordination of other
hardware components within the PC subsystems.
CPU Speed The rate at which data from Applications can be processed
and the techniques of scheduling and the processing of hardware through
the kernel are determined by the CPU chipset and clock frequencies.
Memory Speed and Bus Speed The copying of data to and from main
memory into and out of the CPU can be crucial factors when a lot of
data is being copied to and from the application.
PCI Word Length and Frequency The number of bits that can be transferred
at once across the PCI subsystems (the Word Length) [Gro00]
and the rate at which data can be placed into the PCI bus (the frequency)
imposes a fundamental limit on the rate at which the CPU
and chipset architecture can communicate with NIC hardware.
UDP packets were used to determine the performance characteristics of
a selection of NICs. This is important as the various features of TCP may
impose a performance limit and as such would not give a determination of
the NIC performance, but the performance of the TCP stack itself. The
use of UDP also enables finer control of packet sizes and the rates at which
data is generated and sent to the NIC from userspace without modification
to any underlying systems. As such, the use of UDP packets should give
an indication of the raw performances achievable by suitably programmed
applications.
As such, a series of tests were developed to measure and determine the
performance of the various components that contribute to the performance