An Investigation into Transport Protocols and Data Transport ...

A.2. Network Interface Cards 282
A.2.3
Throughput
Due to the simplicity of the UDP datagram format and stateless nature of
UDP packets, the use of UDP packets to determine throughput can determine
the raw absolute throughput achievable by appropriately designed programs.
The UDPMon [HJ] program was used to transmit a stream of UDP packets
at regular intervals. The rate at which the packets are received can be used
to determine the throughput achieved.
The rate at which data is transferred is determined by two factors:
Packet Size The amount of data in each packet; each packet requires the
necessary overhead of UDP, IP and Ethernet information, each Ethernet
frame must have at least 60B 5 for data communication to occur. As
the amount of application data in each packet is increased, the headers
require a lower relative overhead and performance improves. In all
tests, the ‘wire rate’ is shown which includes all the necessary header
overheads for comparison against the published Ethernet rates 6 .
Inter-packet Time By adjusting the time between the injection of packets
into the network, and assuming constant packet size, the rate at which
data is sent into the network can be increased or decreased. Therefore,
a 1 t
relation between the throughput and the inter-packet time, t, is
expected.
Therefore higher throughputs will be achieved with an increase in the
packet size and by increasing the amount of data that is sent per time unit.
5 Includes: 8B for the inter-packet gap, 6B for the preamble, 18B for the Ethernet
header and CRC, 20B for the IP header and 8B for the UDP header.
6 The actual transfer rates achievable for real data exclude the header overheads.