ECN Capability in the Network Layer

[Feighery, Patrick D.]

I've spent some time changing various parameters within pf.conf that I must
be missing something so obvious.
 
My real goal is to have FreeBSD see either the ECT_0 or ECT_1 bit in the IP
packet (which contains a TCP data segment) and set the CC bits so my
transport layer can react to it.  For testing purposes I am also using pfctl
to emulate a 20,000 bps link, so in theory I won't need any competing flows
to congest the link.  I could use Dummynet to constrain the link, but I have
no idea what the interaction between the two would be. I have set the
interface queue both via sysctl and pfctl to a small number 5.  I should see
and via wireshark do see packet loss.  Therefore, I would expect to set some
parameter which defines a threshold where the ECN CC bit would be set before
packet loss occurs.
 
Is there a problem with RED and constraining my link to 20,000 bps?  
 
Best Regards.
 
    Pat
 
 



  _____  

From: ady at ady.ro [mailto:ady at ady.ro] On Behalf Of Adrian Penisoara
Sent: Tuesday, September 25, 2007 4:05 PM
To: Feighery, Patrick D.
Cc: freebsd-ipfw at freebsd.org
Subject: Re: ECN Capability in the Network Layer


Hi,

  You should lookup the pf.conf(5) man page for the red and ecn scheduler
parameters (as a matter of fact ecn implies red).

Regards,
Adrian.


On 9/24/07, Feighery, Patrick D. <feighery at mitre.org> wrote: 

I am currently trying to integrate an ECN capability into a third
party's transport layer protocol.  In the past I have used Dummynet to
test how transport protocols react under a variety of strange and
non-typical network characteristics.  Now I am trying to use a 
combination of Dummynet and ECN.  Unfortunately after crawling the
network for a few days, I can't really figure out how to configure
FreeBSD to support ECN.  I have been testing with a FreeBSD 6.2
installation and have added the ALTQ into the kernel.  However I can't 
figure out how to create an /etc/pf.conf config file for ECN.  Do I
need to install a different version of FreeBSD to get this
functionality.

Can anyone point me into the correct direction?

Best Regards 

    Pat Feighery

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