> On 15 May, 2015, at 01:22, Kevin Darbyshire-Bryant 
> <[email protected]> wrote:
> 
> 1) Why no ECN marks, only drops?

Probably because your hosts are not requesting ECN from servers, and therefore 
none of the traffic is ECN enabled.  Unfortunately, ECN requests are disabled 
by default in most OSes so far, but many servers will respond to them.

On Linux:
        sysctl net.ipv4.tcp_ecn=1

On Windows Vista and later:
        netsh interface tcp set global ecncapability=enabled

On MacOS X, you need two commands:
        sysctl -w net.inet.tcp.ecn_negotiate_in=1
        sysctl -w net.inet.tcp.ecn_initiate_out=1

Once set, Windows will remember it across reboots.  Linux and MacOS X require 
adding the appropriate entries to /etc/sysctl.conf.

> 2) What falls into diffserv class 0 (alias, why has nothing used it?

Traffic marked with the CS1 DSCP, which corresponds to “background”.  
Supposedly BitTorrent is planned to do that, but I haven’t heard whether it 
actually does so yet.  Application support for Diffserv is generally poor so 
far.

 - Jonathan Morton

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