Re: [PATCH 2.6.16.19 0/2] LARTC: trace control for netem

Thanx for your feedback! We will try to fix this.
Rainer

Stephen Hemminger wrote:

On Wed, 02 Aug 2006 19:21:27 +0200
Rainer Baumann [off-list ref] wrote:

  

quoted

Hi,

We developed an extension to the network emulator netem, that provides
emulation of long term network properties such as long-range dependence
and self-similarity of cross-traffic. It is not possible to emulate
these properties with the  statistical tables for the packet delay
values used by the original netem.

We read the values for the packet delay, drop, loss and corruption from
a pre-generated trace file. This trace file is obtained by monitoring
network traffic and writing all actions to a trace file. During the
emulation the packets get processed according the values in such a trace
file. Detailed information are available on our
Webseitehttp://tcn.hypert.net

A new option (trace) has been added to the netem command. If the trace
option is used, the values for packet delay etc. are read from a trace
file, afterwards the packets are processed by the normal netem functions.
The packet action values are readout from the trace file in user space
and sent to kernel space via procfs.

The evaluation results show similar behavior for our enhancement and the
original netem with respect to packet delay precision and packet loss at
high load (e.g. 80'000 packets per second).
It is possible to add, change or delete multiple netem qdiscs on-the-fly
(original netem qdiscs and trace qdiscs mixed).

We are looking forward for any comments, feedback and suggestions!

Thanks,
Rainer
    

I like the idea and want to get it incorporated.

Major things that need fixing:
* Don't extend size of tc_netem_qopt instead use a new netlink
  payload.
    + add type to TCA_NETEM_ enum
    + new structure containing the payload
  This allows for binary compatiablity.

* Don't use proc for a interface to netem features. Use netlink.
  Either add a new command (or option) to the iproute2 commands
  to handle flow table, or add a new payload.


Minor stuff:
* the bzero macro in netem is a BSDism, just use memset
* bad indentation and style issues.
* minor whitespace damage in several places in patch

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