[Bloat] tc -s qdisc questions

[Jonathan Morton]

> On 15 May, 2015, at 01:22, Kevin Darbyshire-Bryant <kevin at darbyshire-bryant.me.uk> 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