Flow Control in geswitchtem Gigabit Ethernet

Rolf Laich

Semester Work Sommer 1999
Supervisors: Christian Kurmann, Prof. T. Stricker
Institute for Computer Systems, ETH Zürich


Objectives and results

At the laboratory of computer systems at ETH a cluster of PC's is used over a switched Gigabit Ethernet. In order to exploit the performance gains of a Zero Copy driver which operates with speculative packet defragmentation the used hardware components of the network had to be tested with respect to the following questions:

- which possibilities are offered from the hardware to control the flow of data?

- how does the hardware have to be configured to use IEEE 802.3x Flow control?

An additional goal of this work was to propose and implement a protocol to establish an exclusive link between two computers.

The hamachi driver for the PacketEngines GNIC II Adapter could be configured properly to use IEEE 802.3x flow control. But this does not prevent from loss of data under conditions of high network load! The hamachi controller offers further a possibility to receive only data from one specific sender.

The quality of service configuration of the smart switch router was also tested, but the effect of those configurations were not obvious.

Finally a protocol for mutual exclusion in a distributed system was integrated in the driver of the controller. With the implementation of this protocol an exclusive link between two computers could bee established. The time to establish such a link is about 0.5 ms when the receiving machine is not already busy. A throughput of a 40 Mbs link will therefore decrease about 2 % when for every MB of data a link to the partner has to bee established and broken afterwards.

To test the hardware behaviors and to implement the protocol, several modifications of the original hamachi driver were necessary.


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ETH Zürich: Department of Computer Science

Comments to Christian Kurmann <kurmann@inf.ethz.ch>
Date 27-9-1999