Re: [Bloat] Random idea in reaction to all the discussion of TCP flavours - timestamps?

[Jonathan Morton <chromatix99@gmail.com>]

On 16 Mar, 2011, at 3:02 am, Dave Täht wrote:

>>>> 1) Wired devices, where we want to push more 10+ Gbps, so we can assume
>>>> a posted skb is transmitted immediately. Even a basic qdisc can be a
>>>> performance bottleneck. Set TX ring size to 256 or 1024+ buffers to
>>>> avoid taking too many interrupts.
>>> 
>>> To talk to this a bit, the huge dynamic range discrepancy between a
>>> 10GigE device and what it may be connected to worries me. Some form of
>>> fair queuing should be applied before the data hits the driver.
>> 
>> You mean plugging a 10GigE card into a 10Base-T hub?  :-D
> 
> More like 10GigE into a 1Gig switch. Or spewing out the entire contents
> of a stream to one destination across the internet. 

Then that's no different to what I have in my apartment right now - a GigE switch connected to a 100base-TX switch, then to a 2Mbps DSL uplink, which could then be routed (after bouncing around backhauls for a bit) through a 500Kbps 3G downlink to a computer I've isolated from the LAN.

If the flow is responsive, as with every sane TCP, the queue will end up in front of the slowest link - at the 3G tower.  That's where the AQM would need to be.  The GigE adapter in my nettop would be largely idle, as a normal function of the TCP congestion window.

If it isn't, the queue will build up at *every* narrowing of the channel and the packet loss will be astronomical.  All AQM could do then is to pick any real traffic out of the din.

 - Jonathan