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Tsi578 User Manual
June 6, 2016
Integrated Device Technology
www.idt.com
8. Performance
This chapter is a detailed description of the packet switching performance characteristics of the Tsi578.
It consists of the following general topics:
•
•
“Performance Monitoring” on page 188
•
“Configuring the Tsi578 for Performance Measurements” on page 192
•
“Port-to-Port Performance Characteristics” on page 193
•
“Multicast Performance” on page 195
•
“Congestion Detection and Management” on page 196
8.1
Overview
Performance for packet switching is characterized by three measurements: throughput, latency, and
latency variation.
Performance is specified for error free transmission and reception of packets. Performance is specified
for end-to-end transfers through the Tsi578. No performance specifications are made for the different
stages of transfers through the Tsi578.
Performance is specified for a single switch. Performance for larger systems can be computed from this
data.
8.1.1
Throughput
Throughput for packets is a measurement of the amount of packet data that can be transferred in a
given amount of time. It can be presented in different forms:
•
Percentage of a link’s bandwidth (for example, 56% of a 1x @ 3.125 Gbaud)
•
Number of packets of a given size per unit time (for example, 3000 44 byte packets every second)
•
Bit transfer rate (for example, 300 Mbits/s)
Throughput measurements include only successfully transferred packets. Measured throughput does
not include control symbols, retried packets, or other non-packet data transmitted/received on a link
(/K/ and /R/ characters).
8.1.2
Latency
Latency is the amount of time between packet reception and packet transmission. However, the specific
time at which packet reception and packet transmission are deemed to have started must still be
defined. Throughout this document, latency is measured as the time interval between the first bit of the
Start-of-Packet arriving at the ingress of the Tsi578 and that same bit leaving the device.