Papers and Reports
Ethernet Performance
When it comes to real-world network throughput, there are as many
opinions about Ethernet performance as there are Ethernet
installations. Every network site is unique, and the performance of
the network is a function of the number of stations contending for
access to the Ethernet, the type of hardware in use (station
interfaces, switches), the layout of the cables (are they the right
type, right length, and do they meet the config guidelines?), the
quality of the cable installation, the mix of applications, and so on.
The following items help demonstrate that an Ethernet LAN can transfer
data at quite close to the nominal rated speed of the technology.
A
New Binary Logarithmic Arbitration Method for Ethernet.
This paper by Dr. Mart Molle provides a very complete description of
Ethernet performance and documents tests in which the Ethernet channel
was driven to 100% load. The paper also describes the Ethernet channel
capture effect and includes a solution for channel capture based on
modifying the Ethernet MAC. Note that some pages are missing from
this file. The missing pages are composed of a set of full page
figures that accompany the paper, which can be retrieved by clicking
here:
Full page figures for Molle paper
Measured
Capacity of an Ethernet: Myths and Reality, by Boggs,
Mogul, and Kent. From the abstract:"Based on measurements of an
actual implementation, we show that for a wide class of applications,
Ethernet is capable of carrying its nominal bandwidth of useful
traffic, and allocates the bandwidth fairly. We discuss how
implementations can achieve this performance, describe some problems
that have arisen in existing implementations, and suggest ways to
avoid future problems."
Ethernet Channel Capture
Ethernet channel capture is a phenomenon in which the half-duplex
Ethernet media access control (MAC) system can become biased for a
short term toward one station on a heavily loaded network. Under
certain circumstances, this allows a station to more frequently win
the contention for the channel, or ``capture'' the channel, while that
station has something to send.
Usenet posting on Capture Effect.
A short description of how capture effect works can be found in this Usenet posting from Rich Seifert.
The
Packet Starvation Effect in CSMA/CD LANs Part 1
The
Packet Starvation Effect in CSMA/CD LANs Part 2
A paper on the "Packet Starvation Effect," and its effects on
network latency for applications like packet video. "Packet
starvation" is another way of describing the effects of Ethernet
channel capture.
Miscellaneous
The Effect of Ethernet Behavior on Networks using
High-Performance Workstations and Servers.
(Adobe PDF version - approx
96 KBytes).
A technical report from Rich Seifert, one of the original
designers of Ethernet, describing how Ethernets function in the
presence of high offered load from powerful workstations. Includes a
section on the Ethernet capture effect.
Issues in LAN
Switching and Migration from a Shared LAN Environment.
(Adobe PDF version - approx 519 KBytes).
In this technical report Rich Seifert describes how switched Ethernets
function and what issues to consider when planning to implement
switched Ethernets at your site.
Usenet postings about Ethernet collisions.
Two perennial questions about Ethernet are: What is a collision?
and, What rate of collisions are acceptable? These questions are
discussed in this set of Usenet postings.
What is SQE Test and When to Use
It.
The question: "What is the SQE Test signal and when should it be
enabled on outboard transceivers?" is discussed in this document.
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